# Forget Horst, ICT, D-W; here's the holy grail (Merged thread from 4 boards)



## Steve from JH (Dec 30, 2003)

I first heard about this a week or so ago:

http://www.feltequilink.com/

Since then, when not riding my bike, I've been thinking about this design. I've decided it's probably the real thing.

What you have is something that looks like a D-W link but with an extra vertical link connecting the rocker and bottom links. The seat stay and chain stay are carbon and are not connected vertically, so you have a "V" instead of a triangle. The carbon is designed to flex vertically but not horizontally. In fact it has to flex in order for the linkage to move because the rear pivots get farther apart in compression and closer together in extension.

The result is an axle path that is close to a vertical straight line. This means the axle path perpendicular is approximately a horizontal line throughout travel, as though you had a very distant fixed pivot at about the height of the axle.

The advantages would be very low pedal feedback and a highly active suspension. Braking would be like with a parallel floater that always stayed parallel to the ground, making it even more neutral than a real floater. This gives traction advantages. There would also be traction advantages when pedaling, since the loss of thrusting force at the ground would not cause suspension movement.

If it were not for the equilink itself, this kind of axle path would produce very little anti-squat, compared with, say, a D-W link. The bike would tend to squat in the rear with every pedal stroke. But the equilink changes that. Its connecting pivots can be placed to give a leverage bias in favor of extension from the force of the chain tension pulling the axle and BB together. This means that a good amount of anti-squat unrelated to the chain angle can be tuned into the suspension, without producing pedal feedback. You could set it up so that in a middle range gear, at sag, the bike had 100% anti-squat and zero pedal feedback. It would develop some feedback with compression travel, but it would still be very low.

No other design, except for URT's, can claim this. And URT's have all kinds of other problems and have been abandoned as a design.

Unless there is some unforeseen problem, I predict you'll be hearing a lot about this design in the future.

Remember, you heard it here first.


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## Steve from JH (Dec 30, 2003)

*Here's what DT should license*

DT should license and build some of these:

http://forums.mtbr.com/showthread.php?p=2178859#post2178859


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## Jaybo (Mar 5, 2008)

*Interesting...*



Steve from JH said:


> DT should license and build some of these:
> 
> http://forums.mtbr.com/showthread.php?p=2178859#post2178859


We shall see how it rides. I love new technology! But, even more, I like good customer services and pivots that last forever...like a Turner.

Jaybo


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## CharacterZero (May 19, 2004)

The fact that you are compelled to post this in so many different areas draws from your crediblity, and only serves to fragment the ensuing discussion.


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## TIMBERRR (Feb 24, 2006)

Get that FELT garbage out of here!!!!!


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## Jerk_Chicken (Oct 13, 2005)

Just in the nick of time because I suddenly felt that my Turner's rear suspension wasn't working anymore.

Oddly enough, it coincided with me finally getting used to the TNT name. Might need a new buzzword to help me get the riding bug back.


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## MartinS (Jan 31, 2004)

Saw Seamus Mcgraths at Transrockies, definately looks well executed, he did pretty well on it too.


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## indyfab25 (Feb 10, 2004)

I like it...it seems to make perfect sense.


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## cactuscorn (Feb 5, 2004)

a *red* link? but that wont go with my new blue turner jersey. guess ill have to pass.

but really, it looks interesting. but as i say with anything newer, better and a zillion % efficiant, time will tell if it lives up to the marketing hype. when jim felt was still behind the wheel, you could count on good things. i hope this will be true again here.


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## SMR (Apr 20, 2004)

Steve,
how many different forums did you post this on?? Getting a little excited about something no one has ever seen in person or ridden yet? Who knows maybe it will be the greatest, I'll give it a couple years to prove itself.


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## Structure (Dec 29, 2003)

If what I read on the magazine reviews is right the bike looks great in other respects too. Five inches travel, but light. I don't need freeride tough, but I do want a smooth efficient ride. Nice to see another contender.


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## Thylacine (Feb 29, 2004)

Actually I didn't read it here first. Brian Caulfield of Kavik bikes was the first to do that design, and clearly Felt have snaffled him up because very little info can be found about Kavik anymore.

I tried looking for pictures of the prototype he did some 3-4 years ago but for some reason can't find any pix of it on the net whatsoever.


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## derby (Jan 12, 2004)

*I heard it before*



Steve from JH said:


> I first heard about this a week or so ago:
> . . . . .
> Remember, you heard it here first.


Oh that? It's old news. I heard about it before in General, AM, and Other Manufacturers first.

:eekster: :skep: :eekster:

Welcome back!

:thumbsup:


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## ferday (Jan 15, 2004)

thanks Steve. i hadn't seen that.

what a sweet feedback loop....amazing it hasn't been tried before.


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## Thylacine (Feb 29, 2004)

Thankfully, no Felt goons raided my CD collection last night.


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## roy harley (May 8, 2004)

*Very cool!*

Do you know if the Equilink is a Felt own technology or is it a collaboration with someone or some group/company? I am just wondering if we will see other companies with the same Equilink or if this will be a licensed technology like what happened with the Horst link and ICT.


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## Blue Shorts (Jun 1, 2004)

Hey Steve... It sounds great, but did you get a gander at the rear wheel? It's waaay behind the seat tube. I'm curious what the extra long wheelbase and long chainstays will do to the handling.

It is interesting, though.


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## Thylacine (Feb 29, 2004)

Well let's add one and one up shall we.

Type in 'Kavik' into google images and instead of a dozen or so images (including pix of the frame as shown above) like you used to, you get....one pic.

Mr. Caulfield isn't credited on the Felt site, so I would suspect they have either purchased the design from him or just done it anyway and Brian has had to sell his business to pay for the legal fight!

If he's licenced the design I would suspect there'd be a sticker on there saying 'BC Link' or whatever but that doesn't seem to be the case.

Velly Inneresting.


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## totally_fixxated (Aug 24, 2005)

*Suzuki-esque*

Looks similar to the Full-Floater suspension on Suzuki dirt bikes.
I have always liked Kaviks modular dropouts!:thumbsup:


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## cjh_mtb (Jul 1, 2005)

They even know how to spell vertical!










It's so compelling


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## r1Gel (Jan 14, 2004)

Steve from JH said:


> I first heard about this a week or so ago:
> 
> http://www.feltequilink.com/
> 
> Remember, you heard it here first.


First to hear about equilink or your impressions of it? I saw and read about equilink months ago  , and thought, "Boy, Dave Weagle is going to be a rich man with all these copy cats..."


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## Quattro (Dec 26, 2003)

*Has anybody ever ridden one?*

Has anyone ridden a Kavik or a Felt with this suspension, to see if it actually works as the computer says it does?


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## UP Dude (Feb 21, 2004)

It certainly looks impressive. It surprises me that innovative designs are still being released. I have a feeling that we are going to get into an era where everyone settles into their suspension design of choice (in Rocky Mtns case, 5 choices  ) and new suspension designs will taper off. However, the similar prior design from Kavik is an interesting twist. Dwuh, nuh, nuhhhh......

I really like the idea of a vertical hub path. I've thought for some time now that a truely vertical hub path may have some benifits. It can't be vertical through the whole travel, chain growth would be a bit out of hand. So if the travel here is actually vertical, I'm interested to try it.

The one problem I have with it is that it relies on the flex of the rear triangle to move through the travel. It has always been my feeling that a suspension needs to be as stiff as possible (laterally and in line) as to transmit as much of the force as possible to the spring/damper unit. I think a suspension can do a better job if the shock is responsible for all of the vibrations, without uncontrollable variables in the system.

I've never liked Trek Fuels, just not active. This design is completely different, so it may not have the same characteristics. I'm also curious to see if they can make bikes with longer travel. Trek tried to make the liquids with flexing stays and it didn't really work. Now for '07, even the Fuel EX gets a proper pivot. But it does give that snappy, responsive feeling that XC racer types live for. Which is great for racers, but maybe not as much for everyone else.

Time will tell. If they have demos in Vegas, I'll do my best to try one and report back.


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## _dw (Jan 20, 2004)

*governed by physics*

The equilink is governed by the same physics as the rest of the world. The suspension produces some sort of anti-squat curve, and that coupled with the leverage rate is going to govern how the bike responds to acceleration force input. Its that simple. If it makes it easier to comprehend, think of it as a 5-bar link instead of a 4-bar. There is no "feedback loop", no magic voodoo, and certainly no religious intervention.

dw


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## igorion (Oct 12, 2005)

the system has a fixed axle path, and thus is subject to any benefit or problem any other traditional (mono pivot or four bar) system has.

the axle path is not perpendicular by any means, it has a center of curvature that may even fall within the tire radius.

so, not better or worse than any other system from the beginning.

i have spent quite some time playing around with the mechanics of this system and while it has some serious potential that not even felt may have though of yet, it turns out to be a rather conservative system as it is now.

all the systems below are kinematically equivalent (as for drivetrain issues, not for braking)

A










B










C










D










cheers, hannes


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## UP Dude (Feb 21, 2004)

*Jesus is a mountain biker*



_dw said:


> There is no "feedback loop", no magic voodoo, and certainly no religious intervention.


I heard the Catholic church is working on their own suspension for next year. Dubbed the "JC Link", it is supposed to not only float over terrain, but it can also ride on water. It will redefine "all mountain".

It's gonna be sweet. :thumbsup:


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## igorion (Oct 12, 2005)

oh, i even had my original four bar tool adapted to play around with the system...


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## jeffscott (May 10, 2006)

I dont quite get it yet. How does it compare to the Rocky ETSX.


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## Mr.P (Feb 8, 2005)

rigel said:


> First to hear about equilink or your impressions of it? I saw and read about equilink months ago  , and thought, "Boy, Dave Weagle is going to be a rich man with all these copy cats..."


Yea. It seems to be a variation of the DW link - just without the final "kick" in the stroke.

I didn't see any carbon bendy bits, as there was too much marketing speak on the website that turned me off from reading. But Trek did try carbon flexy bits on their Fuel and 5" bike lines. It seemed to work ok for short travel, but it was no substitute for a pivot at 5". Cannondale tried carbon flex chain stays too. Neither design continues, except maybe the Fuel.

P


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## ferday (Jan 15, 2004)

> Dave Weagle is going to be a rich man with all these copy cats...


 

the equilink will be nice competition for the dw, the vpp, and the maestro (and all the others in between...)


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## wyrm (Jan 19, 2004)

What do you think of the braking performance? Would the E-link also neutralize the squat and almost lock up... causing brk jack?


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## chad1433 (Apr 5, 2004)

It looks interesting. It also looks limitless in it's travel abilities. Changing rockers would effect longer travel, so it seems like if they do well with this model, they could have many other bikes in the future.

Looks a bit like a reverse VPP to me.


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## derby (Jan 12, 2004)

*Tongue in cheek?*

I think (at least I hope!) Steve was being cynical or in the spirit of tongue-in-cheek in humor in his original post about the Felt 4 bar 

The Felt rear stays would flex slightly during travel introducing a modification of the axle path and spring rate. The flex tension changes may alter the ride time experience from expected relative effects of path and shock relation to inertia analysis.

The Felt web site seems to be infected with a similar strain of delusional fuzzy physics as Ellsworth's patented mistakes about ICT. :eekster:


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## Steve from JH (Dec 30, 2003)

Hannes, am I wrong in stating that one gear combination and suspension position could have !00% anti-squat and 0 pedal feedback instantaneously? 

I don't think that combination can be achieved with conventional single pivot or 4-bar systems.


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## Ridge Rider (Sep 21, 2005)

Steve from JH said:


> I first heard about this a week or so ago:
> 
> http://www.feltequilink.com/
> 
> ...


I am having a hard time understanding how the system works. The equilink is connected to 2 rotating links that are not parallel. As they rotate it seems that the distance between the end pivots of the equilink will change. Does the equilink flex? I looked at one up close recently at the Trans Rockies race but still didn't understand it. Please enlighten me on this aspect.


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## wyrm (Jan 19, 2004)

AWWW I found the problem...... E type frt derailler...............


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## endurowanker (Mar 22, 2004)

all that really matters is wheel path. anti-swat angle is all about changing wheel path. the claim of "near vertical wheel path" remidns me of specialized's claim on FSR. actually ended up being a less vertical wheel path than a single pivot faux bar. not necessarily a bad thing. in fact a vertical wheel path would actually have more chain growth than FSR. 

this thing doesn't appear to be able to counter out sloppy pedaling any better than FSR, DW, or faux bar. 


i think it's just a game of millimeters at this point. I'm gonna stick wiht what i feel are the most proven and rugged designs. namely FSR and faux bar. probably goin with a faux bar turner next time around.

i'm not saying this thing is bad, i just don't think it's a revolution.


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## 856er (Jul 16, 2005)

Here's some more info

http://www.bikemagic.com/news/article.asp?SP=&v=2&UAN=4855


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## 856er (Jul 16, 2005)

Some more info

http://www.bikemagic.com/news/article.asp?SP=&v=2&UAN=4855


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## 856er (Jul 16, 2005)

Some more info

http://www.bikemagic.com/news/article.asp?SP=&v=2&UAN=4855


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## Steve from JH (Dec 30, 2003)

derby said:


> I think (at least I hope!) Steve was being cynical or in the spirit of tongue-in-cheek in humor in his original post about the Felt 4 bar
> 
> The Felt rear stays would flex slightly during travel introducing a modification of the axle path and spring rate. The flex tension changes may alter the ride time experience from expected relative effects of path and shock relation to inertia analysis.
> 
> The Felt web site seems to be infected with a similar strain of delusional fuzzy physics as Ellsworth's patented mistakes about ICT. :eekster:


No tongue in cheek, except for "Remember, you saw it here first." Obviously, if you didn't see it here first, you can't remember that (unless you have false memories).


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## UP Dude (Feb 21, 2004)

endurowanker said:


> all that really matters is wheel path. anti-swat angle is all about changing wheel path. the claim of "near vertical wheel path" remidns me of specialized's claim on FSR. actually ended up being a less vertical wheel path than a single pivot faux bar. not necessarily a bad thing. in fact a vertical wheel path would actually have more chain growth than FSR.
> 
> this thing doesn't appear to be able to counter out sloppy pedaling any better than FSR, DW, or faux bar.
> 
> ...


I agree. I was thinking this was a pure vertical wheelpath. But "near vertical" is nothing new. I'm gonna have to maintain that at this point, its going to be pretty darn hard to revolutionize suspension. Endurowanker is right, its a game of millimeters at this point. Between FSR, ICT, DW and VPP, how much better can it get? And more importantly, is it worth all of the development and patent costs to do it?

I don't think so. We're at a point where all designs perform very well, and each has their advantages and disadvantages depending on what the consumer wants. This is where style and creativity is frame design take over. Think Ibis and DW. If developing a new suspension that doesn't really do anything significantly better counts as creative style, I would think there are probably better ways to spend that money. But if you can sell it and justify the costs, I guess that is the bottom line.

And maybe I'm dead wrong. Maybe the absolutely perfect suspension has yet to be developed. Maybe it has a completely different form we haven't seen yet, does things we didn't imagine a bike would be allowed to do. That's what makes engineering fun.

Sorry, got sidetracked there. Bikes are cool :thumbsup:


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## UP Dude (Feb 21, 2004)

856er said:


> Some more info
> 
> http://www.bikemagic.com/news/article.asp?SP=&v=2&UAN=4855


Interesting comment in this article that contradicts what I just said.

"It was just biding its time, though. As Felt's Director of Product Development Brian Wilson explained, "We didn't want to just do something that someone else had done - it had to be our design". That's not just a matter of corporate ego - these days you've pretty much got to have your own suspension design to acheive any sort of brand credibility. Specialized has FSR, Marin has Quad-Link, Giant has Maestro and now Felt has Equilink."

I guess everyone does has to have their own design.


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## SCUBAPRO (Jun 29, 2004)

Steve from JH said:


> DT should license and build some of these:
> 
> http://forums.mtbr.com/showthread.php?p=2178859#post2178859


Looks like a DW with a "red band aid". I think the "red cross-brace" might get in the way of the tire so you'll need to extend the chainstay to compensate. Also, the suspension would be less compliant when pedaling due to the cross brace pulling down on the rocker.


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## Dusty Bottoms (Jan 14, 2004)

The techology description actually contradicts itself:

"As you pedal, the red link automatically pulls down on the upper horizontal link, which instantly negates and equalizes weight transfer."

vs.

"By keeping the drivetrain independent of the suspension, it is allowed to perform the job it was solely intended: to propel the bicycle and rider forward."

IT IS IMPOSSIBLE TO KEEP THE DRIVETRAIN INDEPENDENT OF THE SUSPENSION IF THE RED LINK PULLS ON THE HORIZONTAL LINK AS YOU PEDAL!

You also notice they don't say a damn word about braking preformance. This design smells a lot like vpp. 

After a month on a Horst 5 Spot, I can say I like how the design tracks, and it lands medium airs VERY smoothly. However, it still suffers from brake induced suspension lockout, just like every full suspension design I've ever ridden.


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## mbmojo (Aug 9, 2004)

Sure does have a lot of bolts, bushings and/or bearings though.


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## Ridge Rider (Sep 21, 2005)

The equilink is connected to 2 rotating links that are not parallel. Won't the distance between the end pivots of the equilink change as the 2 links rotate? Can someone explain this to me.


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## SCUBAPRO (Jun 29, 2004)

Dusty Bottoms said:


> IT IS IMPOSSIBLE TO KEEP THE DRIVETRAIN INDEPENDENT OF THE SUSPENSION IF THE RED LINK PULLS ON THE HORIZONTAL LINK AS YOU PEDAL!


I agree!!! Until you stop pedaling then the suspension becomes independent of the drivetrain


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## Steve from JH (Dec 30, 2003)

Ridge Rider said:


> The equilink is connected to 2 rotating links that are not parallel. Won't the distance between the end pivots of the equilink change as the 2 links rotate? Can someone explain this to me.


The equilink controls the movement of the rocker and lower link. The rear stays are carbon and must flex because the two rear pivots change in their distance from one another.

Since the rear assembly is not a rigid body, we can consider the chain force translated to the axle as acting separately on the upper and lower links. The pivots of the equilink and the angles of the upper and lower links are designed to give more leverage to the lower link, rotating it forward and causing extension. This extension is designed to balance exactly the compressing force from rearward load transfer from acceleration, in at least one gear combo. The thrusting force from the ground, translated to the axle, produces negligible anti-squat because the axle normal line is very close to horizontal all the way through travel. You could get this 100% anti-squat condition in a gear that had a chain line parallel to the axle normal--thus 0 pedal feedback, at least initially.


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## Bortis Yelltzen (May 18, 2004)

First thing I would do is ride the bike up a rough climb and back down. Then remove the red "Equilink" and do it again. I would be suprised if other than a small amount of flex there is any difference at all. But I would need to ride it to make an offical call.

Based on visual analysis I call BS.

The two links are already fixed together by the rear triangle, so I don't see how adding this extra link changes anything. If you take that link out all you have is a DW-Link/Maestro type design from what I can tell. All I can see is the rear triangle has no brace closest to the seat stay like a DW-Link and VPP bike has, the Felt has a "V" shaped rear triangle where DW/VPP has a closed triangluated rear triangle. Felt then moved/added a "5th" link tying the links together, which in my mind does the same thing a stiff triangulated rear triangle does. The downward angle of the lower pivot link is what is causing chain tension to pull the rear wheel forward (extending the suspension) when pedaling load is applied to reduce squat, the red link is a distraction. The geometry of the two links is what is controlling the wheel path, the red link has nothing to do with that either. And the link driving the shock rotates the same direction as the lower link, therefore it will not function like VPP in terms of wheel path. Now if the "V" shape of the rear triangle is designed to flex and open up and close during extension and contraction of the suspension I could see this little red link might have some effect, but I'm not convinced. I would like to see an animation of some sorts explaining things better, my sketches and free body diagrams are just telling me it is all marketing.

Looks like clever marketing and a way to circumvent the DW-Link and VPP patents by making new claims, even if they are fless than real.

My $0.02

B


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## rzozaya1969 (Nov 28, 2004)

I think there still not a holy grail of suspension. I think it's a great think looking at new designs, I have no idea if this one will be a good or a bad or aregular one, but it's always nice that designers are searching for new stuff.

What I think is that all designers and bike builders post their designs as the ultimate ones, and this is where I get skeptical. I doubt there will be a design that will exceed at all aspects (peddaling while seated, standing up and mashing the pedals, breaking, plushness). One design will favour one at the cost of others. I really don't know much about designs nor the engenieering stuff about it. I have had 2 HL bikes (Moto Lite and Stumpjumper FSR) and a single pivot (Cannondale Jekyll). I have liked all 3, but I prefer the ML and SJ over the Jekyll.


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## Bortis Yelltzen (May 18, 2004)

derby said:


> I think (at least I hope!) Steve was being cynical or in the spirit of tongue-in-cheek in humor in his original post about the Felt 4 bar
> 
> The Felt rear stays would flex slightly during travel introducing a modification of the axle path and spring rate. The flex tension changes may alter the ride time experience from expected relative effects of path and shock relation to inertia analysis.
> 
> The Felt web site seems to be infected with a similar strain of delusional fuzzy physics as Ellsworth's patented mistakes about ICT. :eekster:


My thoughts exactly. Here is a reply I posted in one of the other threads discussing this. It seems to be in-line with what igorion and you have expressed.

First thing I would do is ride the bike up a rough climb and back down. Then remove the red "Equilink" and do it again. I would be suprised if other than a small amount of flex there is any difference at all. But I would need to ride it to make an offical call.

Based on visual analysis I call BS.

The two links are already fixed together by the rear triangle, so I don't see how adding this extra link changes anything. If you take that link out all you have is a DW-Link/Maestro type design from what I can tell. All I can see is the rear triangle has no brace closest to the seat stay like a DW-Link and VPP bike has, the Felt has a "V" shaped rear triangle where DW/VPP has a closed triangluated rear triangle. Felt then moved/added a "5th" link tying the links together, which in my mind does the same thing a stiff triangulated rear triangle does. The downward angle of the lower pivot link is what is causing chain tension to pull the rear wheel forward (extending the suspension) when pedaling load is applied to reduce squat, the red link is a distraction. The geometry of the two links is what is controlling the wheel path, the red link has nothing to do with that either. And the link driving the shock rotates the same direction as the lower link, therefore it will not function like VPP in terms of wheel path. Now if the "V" shape of the rear triangle is designed to flex and open up and close during extension and contraction of the suspension I could see this little red link might have some effect, but I'm not convinced. I would like to see an animation of some sorts explaining things better, my sketches and free body diagrams are just telling me it is all marketing.

Looks like clever marketing and a way to circumvent the DW-Link and VPP patents by making new claims, even if they are fless than real.

My $0.02

B


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## Bikezilla (Dec 19, 2003)

*Just what we need...MORE pivots...*

I'll wait for TE patent his own rendition first.


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## Hardtails Are Better (May 4, 2005)

Bortis Yelltzen said:


> Looks like clever marketing and a way to circumvent the DW-Link and VPP patents by making new claims, even if they are fless than real.


Ding ding ding, we have a winner. Exactly. It's a way to make a DW link without paying DW.


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## tiSS'er (Jan 6, 2004)

I want a suspension design that is capable of doubling my power output  You could call it (TNT)x2.:thumbsup:


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## miles e (Jan 16, 2004)

tiSS'er said:


> I want a suspension design that is capable of doubling my power output  You could call it (TNT)x2.:thumbsup:


Whoah there. Are you suggesting TNT is 100% efficient? I'd hate to see the patent thing rear its ugly head again.


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## tiSS'er (Jan 6, 2004)

miles e said:


> Whoah there. Are you suggesting TNT is 100% efficient? I'd hate to see the patent thing rear its ugly head again.


No, I'm saying DT needs to develop (TNT)x2. It needs to be be 200% efficient  Then I will be impressed with how "efficient" a suspension design is.


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## miles e (Jan 16, 2004)

tiSS'er said:


> No, I'm saying DT needs to develop (TNT)x2. It needs to be be 200% efficient  Then I will be impressed with how "efficient" a suspension design is.


Wow, so the bar has effectively been raised. 200% is the new 100%. Only time will tell who could possibly make such a claim. :yesnod:


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## rbx (Mar 14, 2004)

-Vertical axle paths HAVE chin growth

-Anti squat is calculated from rear tire ground contact and chain line(you cannot only take into consedration chain and rear axle paths)

-Felts says that the red link is attached to the rear lower link and it pull on the upper link to counter squat.well there effectively locking out the suspension (topping the shock)to counter squat-so the system is not fully avtive

My 2 cents


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## MartinS (Jan 31, 2004)

Does that mean it'll only have 5" in the rear?:nono::madmax: 

Sometimes you just have to risk going to hell


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## bitflogger (Jan 12, 2004)

Sorry, but Felt sounds too much like felch.


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## Jet-Mech (Feb 21, 2006)

Bortis Yelltzen said:


> Felt then moved/added a "5th" link tying the links together, which in my mind does the same thing a stiff triangulated rear triangle does. The downward angle of the lower pivot link is what is causing chain tension to pull the rear wheel forward (extending the suspension) when pedaling load is applied to reduce squat, the red link is a distraction.
> Looks like clever marketing and a way to circumvent the DW-Link and VPP patents by making new claims, even if they are fless than real.


Nice analysis Boris Yelltzen. I do see your point about the 5th link being similar to a stiff triangulated rear. I think that there is a subtle difference though. With DW-link / VPP / Maestro, none of the angles in the rear triangle change with suspension movement. With the Felt Equilink, the angle between the seatstay and chainstay does change during suspension movement. Thus, the movement of the instant centre with the Equilink system is governed by the lower link, upper link and Equilink members. An added complexity of the Felt system is the exact stiffness / flexibility properties of the chainstay / seatstay assembly. This is subtly different to the DW-link / VPP / Maestro systems where the movement of the instant centre is governed by the lower link , upper link and swingarm members. The geometry of the Felt system would be unstable with the Equilink removed. Whether the Felt system performs better or worse than other designs I have no idea.


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## Steve from JH (Dec 30, 2003)

Ridge Rider said:


> I am having a hard time understanding how the system works. The equilink is connected to 2 rotating links that are not parallel. As they rotate it seems that the distance between the end pivots of the equilink will change. Does the equilink flex? I looked at one up close recently at the Trans Rockies race but still didn't understand it. Please enlighten me on this aspect.


The equilink controls the movement of the rocker and lower link. The rear stays are carbon and must flex because the two rear pivots change in their distance from one another.

Since the rear assembly is not a rigid body, we can consider the chain force translated to the axle as acting separately on the upper and lower links. The pivots of the equilink and the angles of the upper and lower links are designed to give more leverage to the lower link, rotating it forward and causing extension. This extension is designed to balance exactly the compressing force from rearward load transfer from acceleration, in at least one gear combo. The thrusting force from the ground, translated to the axle, produces negligible anti-squat because the axle normal line is very close to horizontal all the way through travel. You could get this 100% anti-squat condition in a gear that had a chain line parallel to the axle normal--thus 0 pedal feedback, at least initially.


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## Bortis Yelltzen (May 18, 2004)

Jet-Mech said:


> Nice analysis Boris Yelltzen. I do see your point about the 5th link being similar to a stiff triangulated rear. I think that there is a subtle difference though. With DW-link / VPP / Maestro, none of the angles in the rear triangle change with suspension movement. With the Felt Equilink, the angle between the seatstay and chainstay does change during suspension movement. Thus, the movement of the instant centre with the Equilink system is governed by the lower link, upper link and Equilink members. An added complexity of the Felt system is the exact stiffness / flexibility properties of the chainstay / seatstay assembly. This is subtly different to the DW-link / VPP / Maestro systems where the movement of the instant centre is governed by the lower link , upper link and swingarm members. The geometry of the Felt system would be unstable with the Equilink removed. Whether the Felt system performs better or worse than other designs I have no idea.


Interesting. So my statement "Now if the "V" shape of the rear triangle is designed to flex and open up and close during extension and contraction of the suspension I could see this little red link might have some effect" is what you are talking about when you say the angle between the seatstay and chainstay changes. But I sitll don't see how the small amount of flex in the seatstay/chainstay assembly is enough to allow the "equilink" to take over as the driving force in terms of determining the instant center. I could be wrong, it's happened before and will happen again, but I just don't see the equilink and small amount of flex making a large enough difference to make this design heads and shoulders better than any of the other current designs.

If the seatstay/chainstay flex has a lot to do with the functionality of this design that brings up a few more questions.

Where is the seatstay/chainstay flexing the most, at the beginning, middle or end of travel?

I guess to convince me they need to pony up and get some more graphical and quantifiable analysis to back up their claims. Because I keep thinking the little red link is the equivalent of a zero force member in a truss structure.

B


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## AusMTB Orienteer (Jun 30, 2006)

Looking at that picture I can't see how the suspension at the front can do it's job as the stay the is effectively banning it from moving, oh the bottom pivots moves as well. Ah I see so its jobs is to effectively make sure that the upper and lower links stay perpendicular to each other to ensure eveness through the system thus avoiding chainflex etc.


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## uktrailmonster (Oct 10, 2004)

This has cropped up several tims in the last few months. Interesting concept, but I haven't got my head round it yet. From a very quick look I'm not convinced there are supposed to be any flexible parts in this design, but I can't say I've studied it much. However, it does look over-constrained, so perhaps there are. 

Anyway, it will have to do something very useful to warrant yet more pivots, increased friction and weight. Non of these multi-link designs do much for me to be honest. I'm still flying the "simple is better" banner for real world mountain bikes which you have to live with and maintain over several years.


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## UP Dude (Feb 21, 2004)

Bortis Yelltzen said:


> But I sitll don't see how the small amount of flex in the seatstay/chainstay assembly is enough to allow the "equilink" to take over as the driving force in terms of determining the instant center. I could be wrong, it's happened before and will happen again, but I just don't see the equilink and small amount of flex making a large enough difference to make this design heads and shoulders better than any of the other current designs.


If you go to the DW Link website, he has a good animation showing instant center. So if you take that and apply it here, things get kind of interesting. So the solid 4-bar linkage is going to be the frame, upper link, lower link, the equilink, and we'll ignore the rear triangle. Those fixed length pieces determine the motion of the linkage, so one might think that the instant center is defined by the pivot points of those members. But the hub is not moving on the equilink member, its on it's own member (that doesn't have a fixed length). So would the instant center be defined by those points? I dunno. DW told me once that pedalling performance is not determined by the instant center, but braking is. Again, I don't know what that means here, but it may help you others trying to reverse engineer this thing.

I don't know how to go about analyzing this thing. I haven't taken the time to sit down and draw it all out. I do know that its pretty complex as compared to a standard 4 bar. Like DW mentioned above, you can consider it a 5 bar to make it simpler, but the 5th bar doesn't have a fixed length, which makes things interesting. But my gut instinct says that this bike probably isn't a suspension revolution, just another way to make a mousetrap. Not to say the engineers that made it don't deserve credit, its a nice looking design that I'm sure performs well. I don't like that it relies on the rear end flexing, it takes away from the activeness of the rear suspension. But I suppose only riding one will determine it's worthiness.


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## JMH (Feb 23, 2005)

By the way, how many forums did you spam with this exact same post? I am counting 3, but there might be more?

JMH


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## Vrock (Jan 24, 2004)

Too many pivots IMHO, Steve the V "rear Triangle" flex almost an inch but it doesn't modify too much the axle path, There is another model with more travel and it has another pivot near the rear axle on the seatstays.


Happy Trails..


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## Steve from JH (Dec 30, 2003)

UP Dude said:


> If you go to the DW Link website, he has a good animation showing instant center. So if you take that and apply it here, things get kind of interesting. So the solid 4-bar linkage is going to be the frame, upper link, lower link, the equilink, and we'll ignore the rear triangle. Those fixed length pieces determine the motion of the linkage, so one might think that the instant center is defined by the pivot points of those members. But the hub is not moving on the equilink member, its on it's own member (that doesn't have a fixed length). So would the instant center be defined by those points? I dunno. DW told me once that pedaling performance is not determined by the instant center, but braking is. Again, I don't know what that means here, but it may help you others trying to reverse engineer this thing.
> 
> I don't know how to go about analyzing this thing. I haven't taken the time to sit down and draw it all out. I do know that its pretty complex as compared to a standard 4 bar. Like DW mentioned above, you can consider it a 5 bar to make it simpler, but the 5th bar doesn't have a fixed length, which makes things interesting. But my gut instinct says that this bike probably isn't a suspension revolution, just another way to make a mousetrap. Not to say the engineers that made it don't deserve credit, its a nice looking design that I'm sure performs well. I don't like that it relies on the rear end flexing, it takes away from the activeness of the rear suspension. But I suppose only riding one will determine it's worthiness.


You can think of the system as having two competing instant centers. One is what you'd get by ignoring the equilink and assuming the rear is rigid. The other is by using the equilink and ignoring the rear. The end result, allowing for precise flexing of the rear stays in just the desired manner, is an axle path that is close to linear (very slightly curved) and close to vertical (slants slightly rearward). The axle path normal line is not through either IC. It stays close to horizontal throughout travel.

I don't know about revolutionary, but the truly unique feature of this design is the creation of an additional source of torque beyond what is found on other FS bikes. Normally you can calculate the percentage of anti-squat if you know the following things: the location of the intersection of the chain line and the axle path normal, the size of the rear cog and rear wheel, the height of the center of mass, and the wheelbase. All those still apply here. But in addition you have a torque upon the suspension from the chain force acting along the axle path normal line and affecting the lower link and upper link differently, based on the positioning of the equilink.

I haven't worked it all out precisely either, but I've worked out a lot of it. Here's what I think is happening. At 25% sag in a 32/20 gear combo you have a chain line parallel to the axle path normal and both those lines are almost horizontal. That gives you effectively zero anti-squat and zero pedal feedback using the conventional calculation. So the equilink and upper and lower links are positioned to yield 100% anti-squat from the chain force acting to try to flex the rear assembly. So you have 100% anti-squat and zero pedal feedback--the holy grail as far as these two things are concerned.

What happens when you move to other gear combos? When you move to lower gears, you start to develop pedal feedback and some anti-squat of the conventional kind.. The pedal feedback, since it starts from zero, never gets very big. It's much lower than on a DW link, for example. The equilink anti-squat remains about the same. (It falls off very slightly as the chain line moves farther from parallel with the axle path normal--in either direction). But as you move to lower gears, the greater torque on the wheel produces more thrusting force at the ground and therefore more center of mass reaction and more compressing force from load shift. The equilink anti-squat is no longer sufficient to counter the load shift.

But it turns out that the anti-squat from the chain pull angle--the kind found on other bikes--just about exactly compensates. The same thing happens in reverse when you move to higher gears. The result is almost 100% anti-squat throughout the gear range, with relatively low pedal feedback in the lower half of the range and negative feedback (binding of rebound rather than compression) in the upper half of the range. [Edit]: I should make it clear that I'm referring to the gear range in the rear. The chain ring is assumed to stay at 32. When you drop to the small ring, the anti-squat goes well above 100% and when you move to the big ring it goes well below. That's also true of the DW link.

I agree that the flexing of the rear is the potential problem spot. Can carbon technology produce stays that will flex vertically but not laterally and flex vertically precisely as wanted with no slop? The resistance from the flex would seem to be no problem. It simply adds to the spring rate and can be compensated for by using a slightly softer spring. If carbon technology is up to it, then this design seems to be a winner, and is at least somewhat revolutionary.


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## Steve from JH (Dec 30, 2003)

JMH said:


> By the way, how many forums did you spam with this exact same post? I am counting 3, but there might be more?
> 
> JMH


Only one now. I let my editors take care of such details.

Fried spam sandwiches. Yum!


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## Steve from JH (Dec 30, 2003)

Vrock said:


> Too many pivots IMHO, Steve the V "rear Triangle" flex almost an inch but it doesn't modify too much the axle path, There is another model with more travel and it has another pivot near the rear axle on the seatstays.
> 
> Happy Trails..


I didn't know about that. I guess a seatstay pivot could perform the same function as the flexing stays. It gets rid of the flex problem but now you have 7 pivots and 6 bars!


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## CraigH (Dec 22, 2003)

For future reference, from:
http://www.mtbr.com/messageboard/postingguidelines.shtml



> 6. The message has been posted to more than 2 boards. Posting the same message to multiple boards is spam, and all posts may be removed and the user may be banned. Please post to the most relevant board only, no more than 2.


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## Stuart B (Mar 21, 2005)

Bortis Yelltzen said:


> Then remove the red "Equilink"
> 
> B


Hi Bortis

Not sure if this has been commented on, sorry if it has.

Just using my visual inspection....if you removed the red link wouldn't the bottom short link behind the BB be unconstrained and simply rotate down into the the BB, splaying the rear carbon traingle. Kind of turning its self into a stressed faux bar.

Stu


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## Bortis Yelltzen (May 18, 2004)

Stuart B said:


> Hi Bortis
> 
> Not sure if this has been commented on, sorry if it has.
> 
> ...


No, if you remove the red link all you have is a DW-Link bike with a flexy rear triangle, that yes, could compress and fail, but I bet it is strong enough to support riding weight and whatnot. Take a look at a DW bike.

B


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## Stuart B (Mar 21, 2005)

Bortis Yelltzen said:


> No, if you remove the red link all you have is a DW-Link bike with a flexy rear triangle, that yes, could compress and fail, but I bet it is strong enough to support riding weight and whatnot. Take a look at a DW bike.
> 
> B


Not sure I agree, but It will certainly be flexy hehe. I think I might knock a lego model up (yes I'm 29 and couldn't throw my techic lego out hehe...thinking about it....do you get lego in the US lol).

I'll let you all know if I do hehe.

Stu


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## Stuart B (Mar 21, 2005)

right...I have thrown a quick model together. I am not claiming that it is flawless....but I have tried to get all the leverage ratios and pivot points as close to the image as I can by eye.

I didn't make the rear traingle stiff on purpose so that I can see what it would do with out the relying on the triangle stiffness to hold the back end in shape. The bottom short pivot tens to try and rotate up (the opostite way to what I thought) and flip up against the seat tube. There appears to be a significant/noticable amount of flex between the stays for this to work with the beam in place.

Woth the beam the bottom rocker visibly moves, moving the front chain stay pivot rearwards. I haven't compared the difference in this movement for a similar DW setup though. I agree theat DW and this WITH the bar might not right day an night different. But I disagree this would work without the bar in place with out very very unusual/undesirable/damaging behaviour.

By the way...I think its great they have come with a different design.

Stu


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## Steve from JH (Dec 30, 2003)

I guess I should have read those guidelines some time in the last 8 years. I've done this before and nothing happened. It gets a lot of people interested quickly, but it does fragment the discussion.

It is not spam. Spam is unsolicitied junk mail advertising done electronically. I'm not selling anything.


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## Speedub.Nate (Dec 31, 2003)

You guys are missing something: that red link is a piece of taffy!


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## Hardtails Are Better (May 4, 2005)

Hahahahahaha..... Why is the area around the crank in that picture all fuzzy?


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## Steve from JH (Dec 30, 2003)

Bortis Yelltzen said:


> The two links are already fixed together by the rear triangle, so I don't see how adding this extra link changes anything. If you take that link out all you have is a DW-Link/Maestro type design from what I can tell. All I can see is the rear triangle has no brace closest to the seat stay like a DW-Link and VPP bike has, the Felt has a "V" shaped rear triangle where DW/VPP has a closed triangluated rear triangle. Felt then moved/added a "5th" link tying the links together, which in my mind does the same thing a stiff triangulated rear triangle does. The downward angle of the lower pivot link is what is causing chain tension to pull the rear wheel forward (extending the suspension) when pedaling load is applied to reduce squat, the red link is a distraction. The geometry of the two links is what is controlling the wheel path, the red link has nothing to do with that either. And the link driving the shock rotates the same direction as the lower link, therefore it will not function like VPP in terms of wheel path. Now if the "V" shape of the rear triangle is designed to flex and open up and close during extension and contraction of the suspension I could see this little red link might have some effect, but I'm not convinced. I would like to see an animation of some sorts explaining things better, my sketches and free body diagrams are just telling me it is all marketing.
> 
> B


It shouldn't take too much anaylsis to see that the rear stays have to flex or the linkage could not move at all. The only way you could add the red link and have a rigid rear triangle would be if the upper and lower links were parallel and equal in length.

So the red link does indeed have "some effect".


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## Steve from JH (Dec 30, 2003)

SCUBAPRO said:


> the suspension would be less compliant when pedaling due to the cross brace pulling down on the rocker.


I'm glad you see that the cross brace will indeed pull down on the rocker. What this does is try to extend the suspension. Since the load shifts to the rear with each pedal acceleration, this extension can be programmed to exactly cancel the compression that would otherwise occur. That leaves the suspension perfectly balanced and active.


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## Steve from JH (Dec 30, 2003)

Blue Shorts said:


> Hey Steve... It sounds great, but did you get a gander at the rear wheel? It's waaay behind the seat tube. I'm curious what the extra long wheelbase and long chainstays will do to the handling.
> 
> It is interesting, though.


Actually, assuming the distance from axle to tire edge is 13" I get a measurement of 16.3" from axle to BB--rather short.

I found a German site that gives some specs (but not the chainstay length), and for the 19.5" model the wheelbase is 43.8. What's really scary is the head angle, 71.4!


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## akhoundog (Apr 10, 2006)

it's a gimmik. the rear triangle isnt independent.

it's basically just like any other rocker link bike.


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## Dougal (Jan 23, 2004)

It's good to see a truely new design emerging.

Time is a great crap filter. Where are all those Y bikes and Mantra's now?


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## Dougal (Jan 23, 2004)

Bortis Yelltzen said:


> First thing I would do is ride the bike up a rough climb and back down. Then remove the red "Equilink" and do it again. I would be suprised if other than a small amount of flex there is any difference at all. But I would need to ride it to make an offical call.
> B


Without the red "equilink", it would be so flexible as to be unstable. Almost like a five bar linkage with the extra pivot at the rear dropouts.

Note that other VPP style bikes require a brace triangulating the rear swingarm. This does away with that by adding a link that requires the rear triangle to flex.


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## beanbag (Nov 20, 2005)

I don't know why nobody else has mentioned this, but doesn't bob while standing mostly occur when the pedal is pointed downwards? It is the same as just standing on both pedals and bouncing up and down. That's what I notice to be most energy-sapping on a full suspension bike, and this design doesn't do anything to fix that.


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## Jerk_Chicken (Oct 13, 2005)

I still don't see how this design would be the next holy grail. Every so often someone comes up with another ground breaking design that's supposed to destroy all others before it. They all fall to the same fate of being replaced by the next best thing that corrected all the flaws of the previous one. 

This keeps going on while others continue to build and refine great riding, user friendly, and simple bikes that flat out work and feel good to ride.


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## Steve from JH (Dec 30, 2003)

beanbag said:


> I don't know why nobody else has mentioned this, but doesn't bob while standing mostly occur when the pedal is pointed downwards? It is the same as just standing on both pedals and bouncing up and down. That's what I notice to be most energy-sapping on a full suspension bike, and this design doesn't do anything to fix that.


You're right that the design doesn't fix that. In fact, compared to a DW-link, the equilink makes it worse. The only thing you can build into a frame that will combat that kind of rider weight shift bobbing is a fairly high level of pedal feedback. And that compromises activeness.

While that kind of bobbing is not good because it compromises traction, it does not in my opinion sap much energy. The wasted energy would occur on a rigid bike. That's why road racers don't stand up except to break away from other riders. It's a powerful but inefficient riding style.


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## Speedub.Nate (Dec 31, 2003)

Jerk_Chicken said:


> Every so often someone comes up with another ground breaking design that's supposed to destroy all others before it. They all fall to the same fate of being replaced by the next best thing that corrected all the flaws of the previous one.


I think you're speaking too broadly. Sure, there's too much hype & marketing BS out there, but there are a few systems that work really, really well and continue to be refined.

Horst has gone through how many such refinements now, and continues to sit on a lofty pearch.

Weagle's dw-link is the new kid on the block, but has probably been deployed on more bikes than anything but Horst, and it continues to be tweaked and polished to continually improve it.

Even the guys who are selling crap learn a thing or two from the designs that work. (and that's not a comentary on this Felt design). If Felt borrowed a page from Fishers flexing stays and Weagle's emphasis on anti-squat, good for them -- they might have something here.


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## Steve from JH (Dec 30, 2003)

Speedub.Nate said:


> I think you're speaking too broadly. Sure, there's too much hype & marketing BS out there, but there are a few systems that work really, really well and continue to be refined.
> 
> Horst has gone through how many such refinements now, and continues to sit on a lofty pearch.
> 
> ...


If I understand the Equilink design correctly, it might be a good candidate for a Rohloff. I think it's designed to keep 100% anti-squat through all gears in the rear when in the middle chain ring and have very low pedal feedback as well.

If they designed one around a Rohloff (they're both German companies) they could have a 14 speed bike with 100% anti-squat and virtually zero feedback. That's what they claim now, but they're exaggerating.


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## Speedub.Nate (Dec 31, 2003)

Steve from JH said:


> If I understand the Equilink design correctly, it might be a good candidate for a Rohloff. I think it's designed to keep 100% anti-squat through all gears in the rear when in the middle chain ring and have very low pedal feedback as well.


Interesting comment, Steve. However, I've always wondered what effect the Speedhub's torque, or more specifically the anti-torque, has on the suspension.

Whether leveraged against the chainstay, the disc brake tabs, or a Rohloff-specific dropout, both the direction and severity of the anti-torque vary by gear selection (and, of course, pedaling effort).

Dave Weagle helped me choose ideal, dw-friendly ring/cog combos for the three dw-link bikes I set up with Speedhubs. But like you say, It'd be interesting to see a suspension designed spcifically with the Speedhub in mind. When the engineer knows exactly what ring/cog they're designing for, it removes many variables from the system.


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## Steve from JH (Dec 30, 2003)

*Artificial foot?*

For what it's worth, I just learned that the Equilink was borrowed from a design for a prosthetic foot.


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## edouble (Apr 16, 2004)

*That is funny...*



UP Dude said:


> I heard the Catholic church is working on their own suspension for next year. Dubbed the "JC Link", it is supposed to not only float over terrain, but it can also ride on water. It will redefine "all mountain".
> 
> It's gonna be sweet. :thumbsup:


as hell  ,


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## edouble (Apr 16, 2004)

*reading this thread has made me...*

so happy I ride hardtails  .


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## Ridge Rider (Sep 21, 2005)

"The end result, allowing for precise flexing of the rear stays in just the desired manner, is an axle path that is close to linear (very slightly curved) and close to vertical (slants slightly rearward)."

The flexing of the carbon stays is enough to straighten out the circular path?

"At 25% sag in a 32/20 gear combo you have a chain line parallel to the axle path normal and both those lines are almost horizontal. That gives you effectively zero anti-squat and zero pedal feedback using the conventional calculation."

My understanding of pedal feedback is that it is related to chain growth over the range of travel of the suspension. If that is correct and the axle path is close to linear and slants slightly rearward, there should be a large amount of pedal feedback (kickback) during compression of the suspension? Your criteria for pedal feedback is based on one position of the suspension?

"So the equilink and upper and lower links are positioned to yield 100% anti-squat from the chain force acting to try to flex the rear assembly."

Will this action be independent of the stiffness of the flexing carbon spring? The geometry of the upper and lower links appears to provide the anti squat due to the increased leverage on the lower link from chain force, but the flexing spring force has more leverage on the upper link. Both of these will give anti squat but the flexing force will increase as the suspension compresses.


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## Thylacine (Feb 29, 2004)

Steve from JH said:


> For what it's worth, I just learned that the Equilink was borrowed from a design for a prosthetic foot.


Link?

Actually, this looks like the same system


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## Steve from JH (Dec 30, 2003)

> The flexing of the carbon stays is enough to straighten out the circular path?


That's what they claim. I'm accepting their word and the diagram showing the axle path on their website. I don't have any software that can deal with this design.



> My understanding of pedal feedback is that it is related to chain growth over the range of travel of the suspension. If that is correct and the axle path is close to linear and slants slightly rearward, there should be a large amount of pedal feedback (kickback) during compression of the suspension? Your criteria for pedal feedback is based on one position of the suspension?


When the chain line parallels the axle path normal, the rate of pedal feedback is zero. If the lines remained parallel during suspension motion, as with a BB concentric pivot and equal size cogs, then there would never be any pedal feedback.

You can compare the rate of pedal feedback by looking at the angle between chainiline and axle path normal. The larger the angle, the greater the feedback. The Equilink, in this one gear, would start with a feedback rate of zero and it would increase with compression. But compared with, say, a DW link it would never get very high. The DW link's rate decreases, but never falls as low as the Equilink's at its highest.



> Will this action be independent of the stiffness of the flexing carbon spring? The geometry of the upper and lower links appears to provide the anti squat due to the increased leverage on the lower link from chain force, but the flexing spring force has more leverage on the upper link. Both of these will give anti squat but the flexing force will increase as the suspension compresses.


The only role the flexing force plays (aside from modifying the axle path) is to increase the over all spring rate, as far as I can see. This can easily be compensated for by running a slightly softer spring.


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## Ridge Rider (Sep 21, 2005)

"When the chain line parallels the axle path normal, the rate of pedal feedback is zero. If the lines remained parallel during suspension motion, as with a BB concentric pivot and equal size cogs, then there would never be any pedal feedback."

The difference is that with a BB concentric pivot the chain length remains the same throughout the suspension travel (except for the small effects due to the difference in size between the chainring and cog) with a circular axle path centered on the BB, but with this design (if it actually has a nearly linear and nearly vertical axle path) the chain length will grow considerably during compression which will cause pedal kickback.


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## Steve from JH (Dec 30, 2003)

> The difference is that with a BB concentric pivot the chain length remains the same throughout the suspension travel (except for the small effects due to the difference in size between the chainring and cog) with a circular axle path centered on the BB, but with this design (if it actually has a nearly linear and nearly vertical axle path) the chain length will grow considerably during compression which will cause pedal kickback.


With a BB concentric pivot the chain length remains absolutely the same. Difference in size of cogs doesn't matter. A tangent drawn between two circles that are a fixed distance apart is always the same length. Draw two circles on a paper; draw a tangent; and now rotate the paper. Obviously the line stays the same.

There is still pedal feedback, however, if the cogs are different size. It causes "kickback", where the pedal tries to rotate backward, or slows its rotation if it is rotating forward, when the front cog is smaller than the rear--even with a concentric BB. Consider a 22 tooth cog in the front and a 33 in the rear. When the rear rotates around the front the chain will wrap around the rear and unwrap from the front. For every three teeth engaging in the rear, only two teeth can disengage in the front unless the front rotates back one tooth worth. In fact the suspension can not cycle without this backward rotation of the front. This is a significant effect.

Comparing a DW-link in a 32/20 gear with an Equilink I get 20mm of total chain growth for the DW and something like 12mm for the Equilink. But I'm just making an educated guess about the Equilink.

If we consider these two bikes at sag hitting the same bump and only look at a tiny amount of suspension travel, the DW link crank will experience a substantial deceleration, while the Equilink will experience practically none. That deceleration goes against the momentum of your legs and the muscular force you are exerting to accelerate the pedals. The result is a slowing of both the cranks and the suspension.


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## D.F.L. (Jan 3, 2004)

*I'm always late to the party...*

This design looks like it would exhibit a lot of pedal feedback:

On the Felt, the lower link provides the rearward chainstay motion, which isn't countered to a great degree because the upper link moves up as much as it does foward.

VPP links counter each other's motion to provide a PRIMARILY vertical axle path.

I don't know (I haven't ridden one), but it looks like it'll be a great fireroad climber, while being less than ideal on grinding, technical, granny-ring climbs. If so, I'll pass.


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## Steve from JH (Dec 30, 2003)

D.F.L. said:


> This design looks like it would exhibit a lot of pedal feedback.


Read what I said above:

http://forums.mtbr.com/showthread.php?p=2207693#poststop


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## All Mountain (Dec 9, 2005)

ummm.... I bet the Heckler will still smoke it  !


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## keavsh (Sep 13, 2006)

Here are some picture of Felt's Equilink by itself.


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## Dougal (Jan 23, 2004)

Steve from JH said:


> I don't have any software that can deal with this design.


Time to crack out the pencil, ruler and compass then.

Software just makes the process faster and prettier, hand drawings will tell you all the software is capable of telling you (albeit at an accuracy that depends on your pencil width).


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## Steve from JH (Dec 30, 2003)

Dougal said:


> Time to crack out the pencil, ruler and compass then.
> 
> Software just makes the process faster and prettier, hand drawings will tell you all the software is capable of telling you (albeit at an accuracy that depends on your pencil width).


Well this evening I made a little model, using pieces of wooden lath screwed together for the front 4-bar linkage and two lengths of string attached to a pencil for the rear stays. Keeping the the strings stretched taut and cycling the linkage definitely produced a much less curved path than you would get with a regular linkage or swingarm. The center of curvature was probably at least six feet ahead of the pencil (which represented the axle).


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## derby (Jan 12, 2004)

Steve from JH said:


> Well this evening I made a little model, using pieces of wooden lath screwed together for the front 4-bar linkage and two lengths of string attached to a pencil for the rear stays. Keeping the the strings stretched taut and cycling the linkage definitely produced a much less curved path than you would get with a regular linkage or swingarm. The center of curvature was probably at least six feet ahead of the pencil (which represented the axle).


So the physical result is that it would squat and bob a lot if the line from axle to center of curvature was much below passing through the CM, and have lots of pedal bump kickback if a very rearward path, or smooth pedal bump stall like VPP if more horizontal with the axles line.

I did a little cardboard model last night. Depending on the alignment of the connector link the rear two pivots with the stays' distance change would be towards or away from each other, or change not much at all during usable travel range in a "sweet-spot" alignment.

If during compression the rear pivots flex the stays apart then the axle is drawn forward with a relatively tightening path radius, if the stays flex together it would open the axle path radius.

I bet this design really performs best with a high-end platform shock.

It is a very sophisticated design.

Dougal, do Euro seals reduce the stiction of the Nixon? My Nixon Elite is breaking in but even with a couple hundred miles it still has as much stiction as a Fox air shock. Maybe It just needs more miles.


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## Dougal (Jan 23, 2004)

derby said:


> Dougal, do Euro seals reduce the stiction of the Nixon? My Nixon Elite is breaking in but even with a couple hundred miles it still has as much stiction as a Fox air shock. Maybe It just needs more miles.


I'm currently running sherman lowers on my Nixons (original lowers taken off for painting). The enduro seals took about 50-100km of offroad riding to bed in, but now there's no noticable stiction.
I didn't have a stiction problem beforehand, essentially none noticable with the stock seals.
What splash bath lube are you running?


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## Steve from JH (Dec 30, 2003)

Leaving aside URT's and those bikes that somewhat resemble URT's, like the Maverick and I-Drive, you can determine the amount of anti-squat by finding the intersection of the chain line and the axle path perpendicular. If you apply that rule to the Equilink, with its path resembling a low monovpivot, you would have a low level of anti-squat, allowing squat from acceleration, but also a low level of pedal feedback, allowing good compliance when pedaling through bumps.

What you're not seeing is that there is an additional source of anti-squat with this design, and it's unique to this design. The component of the chain's force that acts along the axle path perpendicular, and would therefore tend to neither raise nor lower the axle, acts on the connecting link with its high IC and causes it to move downward, extending the suspension. They can tweak the equilink pivot placements to get as much anti-squat as they want--and it's independent of and additional to the anti-squat determined by the chain pull angle (described above).

So you can come close to the ideal of eliminating acceleration induced squat while at the same time haviing low initial pedal feedback.

The design would not tend to resist bobbing from up and down rider weight shift when pedaling, however. So an on/off platform shock like the RP23 might be the best choice. I recently got one direct from PUSH, with their mods. I got it valved so that it's very plush in the off position. I really like it.


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## igorion (Oct 12, 2005)

i have posted this image on the first page of this thread, i will repost it now to show that the equilink system has no "vertical" wheel path by any means:










steve, i don't agree with your last post.

the wheel path is a result of all the levers in the system working together. if the wheel can move in one direction only, forces perpendicular to that direction will have no effect on the system, however complicated or simple the leverage within the linkage is. that applies just as well to the sixbar linkage that the equilink is. any effects the "red lever" in the equilink system has, are already "implied" in the wheel path.

so, with the equilink, just as with any other system, it is about wheel path direction and nothing else. the wheel path in the equilink is similar to the dw-link (concluded not from of the apparent similarity, but from my analysis).


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## derby (Jan 12, 2004)

Dougal said:


> I'm currently running sherman lowers on my Nixons (original lowers taken off for painting). The enduro seals took about 50-100km of offroad riding to bed in, but now there's no noticable stiction.
> I didn't have a stiction problem beforehand, essentially none noticable with the stock seals.
> What splash bath lube are you running?


The splash bath is still stock, and I hear it's very high viscosity like 30 wt. or something. Closer to a lube than regular 7.5 fork oil. But I would think that wouldn't produce noticeable stiction, just a damping effect. Are you using a more regular rate like 7.5? - or ATF 

I checked the fork stiction again today and the fork is noticeably looser today than a week ago, it's about equal now with the '07 Float-RL I took off my new bike. So it looks like it will soon be noticeably better.

I did run this Nixon Elite fork for about 6 months on the Tracer wound down and it took a few weeks to really loosen up then too. It's just going through the break in again in the unused more extended area of the stantions. The Fox Float rode so smooth right out of the box for an air fork (or any fork) I was concerned the Nixon wouldn't be as smooth over small bumps. I read that PUSH rebuilds using tighter tolerance bushings in the forks so they take a little time to break in too but then are smoother with the reduced slop than broken in stock Fox bushings.

I sure like the handling much better than the Float fork.


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## Ridge Rider (Sep 21, 2005)

"the wheel path is a result of all the levers in the system working together. if the wheel can move in one direction only, forces perpendicular to that direction will have no effect on the system"

Except that the force is acting on the cog which in turn acts on the tire contact patch which produces accelleration which causes squat due to the CM inertia in most designs. The "system" is not just the linkage but the whole bike + rider and it's interaction with mother earth.


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## Steve from JH (Dec 30, 2003)

igorion said:


> steve, i don't agree with your last post.
> 
> the wheel path is a result of all the levers in the system working together. if the wheel can move in one direction only, forces perpendicular to that direction will have no effect on the system, however complicated or simple the leverage within the linkage is. that applies just as well to the sixbar linkage that the equilink is. any effects the "red lever" in the equilink system has, are already "implied" in the wheel path.
> 
> so, with the equilink, just as with any other system, it is about wheel path direction and nothing else.


I see what you are saying and at first glance it seems to be true. If true, then all the claims made by Felt on their website are bogus. I see their claims more as typical manufacturer's exaggerations with a genuine and new principle lying behind them.

Consider the rear assembly from the red connecting link back to the axle. The force acting along the axle normal line will not tend to move the axle up or down and therefore will create no flexing of the rear stays and no pivot movement. That means that this whole rear assembly, with respect to this force line, will behave like a single rigid body with the red link as its leading edge. The force line, passing well below the instant center of the red link with respect to the main frame, will cause the red link to move downward with respect to the main frame and this will then cause flexing of the rear stays and extending of the suspension.


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## Dougal (Jan 23, 2004)

derby said:


> The splash bath is still stock, and I hear it's very high viscosity like 30 wt. or something. Closer to a lube than regular 7.5 fork oil. But I would think that wouldn't produce noticeable stiction, just a damping effect. Are you using a more regular rate like 7.5? - or ATF
> 
> I checked the fork stiction again today and the fork is noticeably looser today than a week ago, it's about equal now with the '07 Float-RL I took off my new bike. So it looks like it will soon be noticeably better.
> 
> ...


I'm using ATF in some of my forks and 15w40 engine oil in others. Basically I'm riding around on a lot of guinea pigs with different fluids to see which ones have issues.
The 15w40 does seem smoother than th ATF.

My Nixon was second hand when I bought it (very little use though) so I don't know what the initial breakin was like.


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## Ridge Rider (Sep 21, 2005)

igorion said:


> i have posted this image on the first page of this thread, i will repost it now to show that the equilink system has no "vertical" wheel path by any means:
> 
> 
> 
> ...


Please explain the axle path that looks something like a hysterisis loop. How was it generated? Does it take into account the flexing of the rear stays?


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## Dougal (Jan 23, 2004)

Ridge Rider said:


> Please explain the axle path that looks something like a hysterisis loop. How was it generated? Does it take into account the flexing of the rear stays?


I think it's due to one of the links turning completely over centre.


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## igorion (Oct 12, 2005)

i have put the little tool the screenshot was taken from online! the app is very basic but gives you a pretty good idea how the six-bar "equilink" system actually works. you can even drag the pivots around to simulate different setups.

igorion's six-bar test app

yuo will have to install adobe's svg-viewer to be able to run the animation:
svg-viewer download (free)

@steve

i wouldn't have picked the word "bogus", but if that's what you want to call it, i agree. just like many other manufacturers felt is selling it's system to custumers and tries to give them a plausible explanation why exactly their system is "the one". don't get me wrong, i think the equilink is a very capable system, especially after rider reports being so positive, but what i am trying to say is that their system is not better "by nature". like i said before, the system has a fixed axle path and as such is subject to any advantages or disadvantages that four-bars or mono-pivots (or most other systems) have.

as for your theory about the extra instant center the red link has, i don't agree. again: if the force at the axle is perpendicular to it's path that means the ENTIRE system will be unaffected (motion-wise) by that force. while there may be forces acting upon the red-link, those forces will be balanced by the other links in the system.

@Ridge Rider

you are charging open doors with your comment about forces at cog, contact patch etc.
still, after having considered all those forces, you will end up with a resulting force at the axle. that force i have been referring to.


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## Steve from JH (Dec 30, 2003)

igorion said:


> as for your theory about the extra instant center the red link has, i don't agree. again: if the force at the axle is perpendicular to it's path that means the ENTIRE system will be unaffected (motion-wise) by that force. while there may be forces acting upon the red-link, those forces will be balanced by the other links in the system.


The argument comes down to the answer to this question: Is it possible to build a simple mechanical device that has a moving part with a defined path, such that a force exerted on that part in a direction perpendicular to its path can cause it to move along its path?

As I said before, at first glance the answer would seem to be no.


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## derby (Jan 12, 2004)

*igorion says it much better*



Steve from JH said:


> The argument comes down to the answer to this question: Is it possible to build a simple mechanical device that has a moving part with a defined path, such that a force exerted on that part in a direction perpendicular to its path can cause it to move along its path?
> 
> As I said before, at first glance the answer would seem to be no.


I try not to argue, just present perspective, and let evidence confirm.

The red link is not in any way part of a solid body with the axle point. The red link would be a link of a 5-bar system, if considering under any tension the flex links rotate around an axle centered pivot (there might be a different virtual center between the flex stays), and not considering the frame link. 2 pairs would have to be in straight alignment with each other of the 5 bars to produce a link-locked triangulated solid-body effect of the red bar with the axle.


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## NorKal (Jan 13, 2005)

Dusty Bottoms said:


> However, it still suffers from brake induced suspension lockout, just like every full suspension design I've ever ridden.


So how is a hardtail any different?
When you brake on a hardtail, there is no suspension.
When you pedal on a hardtail there is no suspension.
When you land a jump on hardtail, there is no suspension.


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## uktrailmonster (Oct 10, 2004)

Khemical said:


> So how is a hardtail any different?
> When you brake on a hardtail, there is no suspension.
> When you pedal on a hardtail there is no suspension.
> When you land a jump on hardtail, there is no suspension.


Well that's why some people prefer to have rear suspension in the first place. HTs are not noted for their rear braking stability - they just skip and bounce off things. A locked out suspension tends to do the same, although mine certainly doesn't lock out on the brakes.


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## fat_weasel (Jan 9, 2005)

Word.


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## MartinS (Jan 31, 2004)

Demo'd one at interbike and have to say it was the nicest riding trailbike I tried - sure kicked the surprisingly dissappointing BMC - 22.5 top tube on a 19" -stumpy- and the Yeti 575. I have a lot of time on the Blur LT and the Felt felt (Felts'?) smoother and torsionally stiffer - I don't think it will suffer the classic Blur "creak" but time will tell - they are also doing a 6.5" version called the Redemption.Of the friends I talked to at the show the Felt was the highlight for those who tried it - even a buddy whose shop dropped Felt last year is now regretting it. An extremely impressive first shot at a fully!


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## Ridge Rider (Sep 21, 2005)

igorion said:


> i have put the little tool the screenshot was taken from online! the app is very basic but gives you a pretty good idea how the six-bar "equilink" system actually works. you can even drag the pivots around to simulate different setups.
> 
> igorion's six-bar test app
> 
> ...


I have used your animation tool - thank you for that. After using it I see that the actual axle path is only approximately the middle 1/3 of the right hand side. This portion has some curvature but does not appear to be overly tight. If we include the flexing of the rear carbon stays won't this axle path straighten out a little assuming that the flex is distributed along the stays and not like a pivot at the axlw?


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## Steve from JH (Dec 30, 2003)

Ridge Rider said:


> I have used your animation tool - thank you for that. After using it I see that the actual axle path is only approximately the middle 1/3 of the right hand side. This portion has some curvature but does not appear to be overly tight. If we include the flexing of the rear carbon stays won't this axle path straighten out a little assuming that the flex is distributed along the stays and not like a pivot at the axlw?


I was trying to say much the same thing in this thread: 
http://forums.mtbr.com/showthread.php?p=2286239#poststop


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## Kavik (Apr 13, 2007)

Thylacine said:


> Actually I didn't read it here first. Brian Caulfield of Kavik bikes was the first to do that design, and clearly Felt have snaffled him up because very little info can be found about Kavik anymore.
> 
> I tried looking for pictures of the prototype he did some 3-4 years ago but for some reason can't find any pix of it on the net whatsoever.


Warwick,
What's up man? Just stumbled on MB Action and then found this thread. PM me if you would like to hear a funny story.


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## Thylacine (Feb 29, 2004)

And by snaffled I mean RIPPED OFF.

Fark. I keep typing stuff but then realise words cannot express how morally reprehensible I think Felt is at this point.

I met Bob Felt in 2002. Seemed like a good bloke.

Clearly I couldn't be more wrong.


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## All Mountain (Dec 9, 2005)

Thylacine said:


> And by snaffled I mean RIPPED OFF.
> 
> Fark. I keep typing stuff but then realise words cannot express how morally reprehensible I think Felt is at this point.
> 
> ...


Just read the news on your site.... 2+2 ain't hard to add up


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## DeeEight (Jan 13, 2004)

Didn't Kavik do some really sexy elaborate dropouts also? Peyto was running them for awhile on their frames and then stopped offering them a couple years ago. 

I'm not surprised Felt ripped his design, its quite common in the bicycle world to rip suspension linkage designs from other companies. What's his name Busby who does the GT designs suddenlly discovered 'horst-links' all on his own when the RTS was just entering production and Mongoose was already putting amplifiers on the market. 
Sweetspot dude just happens to "invent URTs with a pivot in the middle of the frame" a few years after the Trimble/OneOff Titanium full suspension bikes appear at Interbike and in a few bike mags. You always wonder when a company with practically no experience in a field like full suspension bikes, let alone little in mountain bikes overall suddenlly leaps ahead in suspension designs.


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## Kavik (Apr 13, 2007)

coincidence?


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## tscheezy (Dec 19, 2003)

MartinS said:


> Demo'd one at interbike and have to say it was the nicest riding trailbike I tried...


Odd. The one we rode was just average overall:



tscheezy said:


> Dirt Demo impressions: Felt makes two major flavors of the Equalink- one more trailbike-ish and the other more xc-ish. The trailbike version has a beefier downtube and a somewhat shorter and more upright cockpit. Both versions apparently get 5" of travel in the back. The Virtue Two that we rode was the more xc version. There was no way this bike felt like it got 5" of travel even though we were getting all the travel the bike offered based on how far the o-ring was getting pushed down the shock's shaft. The suspension seemed to get overwhelmed by trail chop and it bobbed out of the saddle as much as most bikes. Nothing special here that I could tell. Square edge hits and washboard sucked the momentum out of the bike and spikey hits made it feel more like a 3.5 or 4" rig. The geometry was nice for an xc rig but the wheelbase felt pretty long, which made it handle well at speed. It had a somewhat tall feel to it also, but it was balanced and easy to rail through corners. The bike was quick and lithe like an xc race rig but exhibited a somewhat harsh suspension feel to match. I would be curious to try the trailbike version for comparison.


Just a thumbnail impression, but unless the RP23 was defective, I'm not sure what would change over time. There is only one review product review section here of the Felts, and the guy also mentions out-of-the-saddle suspension movement. He came from 15 years on a hardtail so what I consider harsh, he may consider plush.


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## bigpedaler (Jan 29, 2007)

my 2c....

since there are so many different types of riers out there, with different ideas about how a bike should feel, there is NO 'holy grail'. there are more popular designs than others, but no one is that much better than all the rest.

the horst link proved its limitations in the NRS.
the 'faux-bar' works wonderfully with some sort of SPV.
dw-link shows great promise, but long-term results are still not in, not enough time after intro. (the '03 ddw's were faux, as well, just ask dw himself)
vpp has shown its drawbacks in lackluster climbing, and thus are not for climbers, just for nearly everyone else.

people, it's a matter of taste/choice; the more 'new' designs we see, the more clunkers are going to show up (see giant VT). let the people who like a design run it, the ones who need to experiment play w/ it, and the rest -- who know it's more about the ride than the equipment -- will just be out there pedaling!


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## Thylacine (Feb 29, 2004)

DeeEight said:


> Didn't Kavik do some really sexy elaborate dropouts also? Peyto was running them for awhile on their frames and then stopped offering them a couple years ago.


Yeah, and then if you search the pic archives on this site, you'll see Dean sporting them too.

Except they're not Kaviks, they're direct ripoffs too.

This is a fcking joke.  :madmax:


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