# Full suspension frame build



## JCRacing (Dec 20, 2007)

Ok, I have been reading this forum for a few months now and I can't seem to understand why not many frame builders on here are working on a full suspension frame design? Is it just out of most builder's leagues or are most of the people on this forum more into building hard tails? I have been researching different types of rear suspension designs and resently started CADing up a design I would like to persue, but every time I come to this forum in hopes to find other builder's thoughts and ideas on rear suspension design, I only seem to find quotes such as, "stick with a hard tail design." Can someone shed some light on rear suspension design, pivot location, compression rates, bearing selection, etc? Or point me in the right direction for more research on this subject? I am working on a design in SolidWorks that is a four bar linkage system similar to Jamis/Chumba/Nicolai and I would like to find more info on this style suspension design. I am at the point of chosing bearings for the system and I would like to go with IGUS I-Glide bearings...does anyone have any experience with these for full suspension pivots? Any advise would be greatly appreciated! 
Thanks,
Jason


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## brant (Jan 6, 2004)

Surely many of the reasons "not many frame builders on here are working on a full suspension frame design" are the reasons you go on to ask questions about in your post?


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## heeler (Feb 13, 2004)

If you are "at the point of choosing bearings" then you are way ahead of the rest of us...


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## brant (Jan 6, 2004)

On-One said:


> If you are "at the point of choosing bearings" then you are way ahead of the rest of us...


Personally I've always thought that I'd just use headset or BB bearings.


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## Walt (Jan 23, 2004)

*Encouragement, and answers:*

JC -

First off, good on ya for being interested in FS bikes. I build some myself, but they're most single pivot bikes for DH/FR, so I don't have much specific feedback for you about 4-bar designs.

The reason that FS/CAD threads generally recieve a negative response here is that I've yet to see a case of one of the FS/CAD design threads actually turning into a bike. IMO, unless you're going to have someone else do the building, it's much better to start small and learn about metalworking and construction first (in part, so that you'll know what some of the design challenges really are when the end mill hits the 6061). CAD drawings of full suspension bikes are a dime a dozen on MTBR. Homebuilt full suspension bikes are virtually nonexistent. Without being negative: The best way to get some more constructive attention is to post some pics proving that you're actually attempting to build the bike, rather than sitting in the back of your ME lecture doodling on Solidworks.

You might email Sherwood at Ventana and see what he uses for bearings. I've found a good selection online (in small quantities) at VXB, as well. For my single pivot bikes, I use a BMX bottom bracket for the main pivot, which is super stiff and very, very durable. For a 4-bar setup, you'll obviously want smaller (lighter) bearings. I would make sure that you can replace them if needed and not stress too much about brand or type, if this will be a prototype. It might suck, and then you'll have wasted big $ on fancy bearings.

-Walt



JCRacing said:


> Ok, I have been reading this forum for a few months now and I can't seem to understand why not many frame builders on here are working on a full suspension frame design? Is it just out of most builder's leagues or are most of the people on this forum more into building hard tails? I have been researching different types of rear suspension designs and resently started CADing up a design I would like to persue, but every time I come to this forum in hopes to find other builder's thoughts and ideas on rear suspension design, I only seem to find quotes such as, "stick with a hard tail design." Can someone shed some light on rear suspension design, pivot location, compression rates, bearing selection, etc? Or point me in the right direction for more research on this subject? I am working on a design in SolidWorks that is a four bar linkage system similar to Jamis/Chumba/Nicolai and I would like to find more info on this style suspension design. I am at the point of chosing bearings for the system and I would like to go with IGUS I-Glide bearings...does anyone have any experience with these for full suspension pivots? Any advise would be greatly appreciated!
> Thanks,
> Jason


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## Evil4bc (Apr 13, 2004)

JCRacing said:


> Ok, I have been reading this forum for a few months now and I can't seem to understand why not many frame builders on here are working on a full suspension frame design? Is it just out of most builder's leagues or are most of the people on this forum more into building hard tails? I have been researching different types of rear suspension designs and resently started CADing up a design I would like to persue, but every time I come to this forum in hopes to find other builder's thoughts and ideas on rear suspension design, I only seem to find quotes such as, "stick with a hard tail design." Can someone shed some light on rear suspension design, pivot location, compression rates, bearing selection, etc? Or point me in the right direction for more research on this subject? I am working on a design in SolidWorks that is a four bar linkage system similar to Jamis/Chumba/Nicolai and I would like to find more info on this style suspension design. I am at the point of chosing bearings for the system and I would like to go with IGUS I-Glide bearings...does anyone have any experience with these for full suspension pivots? Any advise would be greatly appreciated!
> Thanks,
> Jason


What your asking is the basis behind the complex engineering of a suspension frame , IE: controlled movable structure 
Hardtails are somewhat easy to build and understand.
Full suspension bikes are much more complicated , not too be rude but we aint gonna do the work for you 

Pivot location : this can change everything in your design , it also effects the compression ratio and shok stroke.
If you have solid works , you have the capabilities with this and some basic math to figure out the design of a suspension frame and calculate compression ratio and effective shok stroke.

Bearings: this is basic engineering , you have to get a bearing catalogue and research what bearing is going to work best for your design , Wile most manufactures use various bearing sizes and QTY's for their pivots you are really gonna have to do your homework here , almost every bike is different.

It sounds like you have a pretty god idea of what your doing , I'm not going to lie a good suspension frame take allot of time , multiple revisions and then costly prototypes and production samples . If your engineering is spot on you may have only a few prototypes and samples , but look at the new version of the Blur Santa-Cruz went thought 5 test mules before they got it right , and they have a in house engineering staff, prototype facility and access to the best factories in the world.

I'm currently working on a full suspension design and wile it's been a work in progress over the past 10 years , the current revision i have that is almost ready to be prototyped has over 200 CAD hours .

There are allot of people who can make a full suspension bike , only a handful can make a quality full suspension bike that works properly !

Good luck , your starting in on the hardest part of the bike design world , suspension design .


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## pvd (Jan 4, 2006)

Walt said:


> The reason that FS/CAD threads generally recieve a negative response here is that I've yet to see a case of one of the FS/CAD design threads actually turning into a bike. IMO, unless you're going to have someone else do the building, it's much better to start small and learn about metalworking and construction first (in part, so that you'll know what some of the design challenges really are when the end mill hits the 6061). CAD drawings of full suspension bikes are a dime a dozen on MTBR. Homebuilt full suspension bikes are virtually nonexistent. Without being negative: The best way to get some more constructive attention is to post some pics proving that you're actually attempting to build the bike, rather than sitting in the back of your ME lecture doodling on Solidworks.
> 
> -Walt


Yup, Yup.

Walt's right. It's easy and cheap to sketch something up in CAD. Tooling up, paying out cash, and building one is a whole different thing. Most people never get that far.

One issue is that aluminum is the correct material for FS. Ever try to find 7005 with all the sizes you need? ha. 6061, have a talk with your local heat treater and just wait 'till you hear about the batch cost. Then become a '*****in AL welder in just a few years.

I build hardtails now because it's easy. It's that simple. I can play with fit and geometry at $300 a whack. I like that. I expect to do FS in the next year, but it's a whole differnt leauge and the time, $$, and tools are just magnified. I do still have a day job and i'd like to ride sometime.

Most builders suggest to build a hardtail first because it is very good advise. It's cheap (comparatively), and get's you exposed to the fundementals of actually desigining a real bike and producing it. Baby steps. If you can pull off a hardtail, then you are welcome to consider the next step.


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## surlytman (Nov 9, 2005)

Go to your local bearing supply house, be nice and ask them if they have an older bearing reference guide you can have. I have a catalog from CR Bearings, about 1.5" thick...(was researching headset ideas)........I get wood reading through all the sizes and types of bearings.


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## swift (Apr 3, 2007)

+1 with Walt and PVD.
I'm interested in Full Suspension, myself but I'm not trying to put the cart before the horse. After my construction skills are up to par, per my own perfectionist standards, I plan to move into full suspension. ...But not before. As pointed out, steel hardtails make practice 'affordable' so the project list can grow without breaking the bank.


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## rockyuphill (Nov 28, 2004)

NSMB has a nice little writeup of the prototyping process than Santa Cruz went through for their new Blur LT frame with shots and descriptions of all the test mules they built.

http://www.nsmb.com/gear/blurLT_02_08.php

Which I think underlines points raised here; just because you can design it and build it, that's no guarantee you'll like the ride. You gotta figure that a company like SC has many experienced people and all the groovy design software, but it still comes down to building them, riding them, building a different one, riding it, building a different one, riding it....

All of which would consume a stack of resources and time.


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## themanmonkey (Nov 1, 2005)

pvd said:


> Walt's right. It's easy and cheap to sketch something up in CAD. Tooling up, paying out cash, and building one is a whole different thing. Most people never get that far.


*PVD* is on the right track. I don't think most non-builders understand how much it costs for tooling. The parts and tubes for a hardtail are cheap. I've built a few softtails and they're pretty cheap too. When you start adding linkages and machined brides and mounts things get really expensive quick. I talked to Noel at Knolly Bikes quite a bit about this stuff over the years and some of the development costs blew my mind. Once you start talking 100,000 units like Specialized and Kona economies of scale come into play, but for the single builder it's tough you develop your own design.

Of course if you're a full-time insured builder you can buy a rearend and all the braze-ons from Ventana and go from there. That's what I'm doing next year.
best,
MonkeyB


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## Evil4bc (Apr 13, 2004)

themanmonkey said:


> *PVD* iOf course if you're a full-time insured builder you can buy a rearend and all the braze-ons from Ventana and go from there. That's what I'm doing next year.
> best,
> MonkeyB


That a good route to go for a affordable rear suspension platform .
I build a few of thoes already and they can be built into some pretty cool bikes.


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## rockyuphill (Nov 28, 2004)

And Risse Racing does the modular rear suspension bits to provide those fussy to fabricate applications.

http://www.risseracing.com/product_frames.shtml


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## JCRacing (Dec 20, 2007)

Walt, and all, here is a picture of my design thus far, (hopefully it attached, sorry, I am new to this). You will notice the drop outs...they are designed to accept the Rockshox Maxle 12mm rear through axle. Obviously I have my work cut out for me on the rear end, hence the reason I posted this thread. I would like to find people who have done what I am doing and get some suggestions, cretiques, etc. Oh, and the tubing I selected thus far is all Easton.

To answer some of the comments about my post, yes, I am an ME, working full time now in the aerospace industry and also share the passion to design and build my own frame. What forced me into this was I actually bought a SC Blur and was not as impressed as I thought I would be. The Blur is now my wife's bike. I looked into a multitude of different rear suspension designs and read a lot of articles/reviews about the different designs. I just could not bring myself to spend $2,000 on a frame. I would prefer to spend the $2K on a tig welder that I will have for the rest of my life and build my own, even though I know I will spend over $2K, at least I will have more than a frame to say for it, and dramatically increased knowledge from designing it and more respect for the finished product, even if it doesn't turn out the way I hope.

I took on this personal challenge because I know the tools that are needed for this, such as SolidWorks, CosmosMotion and CosmosWorks, (I'm actually attending a training class through my work for Cosmos in 2 weeks), (which to answer someones question, I plan on analysing the rear suspension design in Cosmos), and I basically grew up in the shop welding and fabricating offroad trucks, etc., (and I went through the ROP cert program for acr and MIG, also took classes in TIG and am recently a CWI). So I convinced myself that I have what it takes to do this and could not possibly justify spending the money any other way...buy assets not liabilities right? Also, I have done a lot of work with a local machine shop that is willing to help me machine the parts at little cost, also a huge reason why I am doing this.

I appreciate your thoughts and comments, keep 'em coming!! And any articles, anything related to FS frame design, please let me know!!

Thanks,
Jason



Walt said:


> JC -
> 
> First off, good on ya for being interested in FS bikes. I build some myself, but they're most single pivot bikes for DH/FR, so I don't have much specific feedback for you about 4-bar designs.
> 
> ...


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## JCRacing (Dec 20, 2007)

Very cool!! Thanks for the risse link!!



rockyuphill said:


> And Risse Racing does the modular rear suspension bits to provide those fussy to fabricate applications.
> 
> http://www.risseracing.com/product_frames.shtml


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## Walt (Jan 23, 2004)

*I think Risse is out of business.*

I tried to get parts for an old Trixxy fork a few years ago and they didn't respond to emails. Not sure if the company is still in existence.

Just FYI. I have nothing against Risse (well, except that the Trixxy was a big POS).

-Walt



rockyuphill said:


> And Risse Racing does the modular rear suspension bits to provide those fussy to fabricate applications.
> 
> http://www.risseracing.com/product_frames.shtml


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## Walt (Jan 23, 2004)

*Where are the pivots?*

It looks like you've got a pivot above and behind the bottom bracket, and another on the seatstay - so wouldn't this be a faux-bar or glorified single pivot design, rather than a true 4-bar? I'm not trying to start an argument, as I'm far from an expert on suspension design, but I think this is really a single pivot design with a linkage activated shock, no?

*If* I'm reading this right, you've got a standard single pivot axle path, with (I'm assuming) some kind of shock mounted to the downtube or toptube that your seatstays will connect to directly. Am I reading the drawing right?

For what it's worth, I think you won't find any other examples of people devoting these kinds of resources to a one-off full suspension bike. You're kind of on your own for a lot of this - I think the biggest challenge (given your skill set) will probably be finding material to build the rear end with. 70 series aluminum isn't easy to come by, and 60 series is going to require a lot of extra heat treating and alignment work, which is expensive and no fun. Check Fairing Industrial (www.fairing.com) - they supply some decent stuff in 7075 that might work (PVD, have you seen this?). For example:
http://fairing.com/bicycle_frame_depot.asp?subcat=a76
http://fairing.com/bicycle_frame_depot.asp?subcat=a76&subButtedTube=bsp

Downside is that I think they require 50+ piece orders. But I'm not positive about that. I make big steel tubing orders from them pretty regularly, so I can ask if I can slip some Al bits in with the next one if anyone is interested.

Out of curiousity, what didn't you like about the Blur? How is your design different/better? At a glance, your design looks virtually identical, though obviously I don't have a really accurate way to compare them. Do you plan to build and test some prototypes, or is this going to be a one-shot deal?

-Walt



JCRacing said:


> Walt, and all, here is a picture of my design thus far, (hopefully it attached, sorry, I am new to this). You will notice the drop outs...they are designed to accept the Rockshox Maxle 12mm rear through axle. Obviously I have my work cut out for me on the rear end, hence the reason I posted this thread. I would like to find people who have done what I am doing and get some suggestions, cretiques, etc. Oh, and the tubing I selected thus far is all Easton.
> 
> To answer some of the comments about my post, yes, I am an ME, working full time now in the aerospace industry and also share the passion to design and build my own frame. What forced me into this was I actually bought a SC Blur and was not as impressed as I thought I would be. The Blur is now my wife's bike. I looked into a multitude of different rear suspension designs and read a lot of articles/reviews about the different designs. I just could not bring myself to spend $2,000 on a frame. I would prefer to spend the $2K on a tig welder that I will have for the rest of my life and build my own, even though I know I will spend over $2K, at least I will have more than a frame to say for it, and dramatically increased knowledge from designing it and more respect for the finished product, even if it doesn't turn out the way I hope.
> 
> ...


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## pvd (Jan 4, 2006)

JCRacing said:


> Oh, and the tubing I selected thus far is all Easton.


Ha! If you are designing around a specific tube, you should be holding it in your hand. Lots of tubes are listed by Easton, Nova, and Fairing, but most of them are not available or are only available in large quantities. The stuff that is, sucks.

Your design is just a simple swingarm circa 1990. If you didn't like the Blur, your going to hate this. It's also not finished. You have done none of the hard work, just some main tubes. The pivots are not detailed, the bosses not present, the shock not included, no wheelpath, wheel rate, or spring calculations. Basically, you have a paper napkin sketch.

It sounds like you are a little green to be be doing an AL FS bike. Being a ME is a far cry from actually making something on your own. Tooling up and doing everything on your own is also a far cry from welding some fenders up at your bro's shop. From everything you have said, the advise is still to build a hardtail first. A materials will be less than $200. You will find out pretty quick that you will spend another $5-8K at least to build a quality bike that you would need to for a decent FS start.

This is why not many frame builders on here are working on a full suspension frame design.


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## rockyuphill (Nov 28, 2004)

If you want to get a sense of how subtle the effects of pivot placement, linkage design, shock choice, etc. etc. etc. are on the suspension characteristics, grab a $25 personal copy of Linkage 2. It has several hundred existing bikes in the database and you can enter your own. It spits out all the pertinent info on leverage ratio, chain growth, pedal feedback (which I'll bet it what you didn't like about the Blur - same reason I got ride of mine shortly after buying it), so you can compare a bunch of different suspension designs.

http://www.bikechecker.com/index.php?pers

Once you have this software you can go ride a bunch of different suspension bikes to see which bikes feel the best, then go back and look at what sets one design apart from another.


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## TacoMan (Apr 18, 2007)

If you re-design the pivots, you can make it from steel which is easier to work with on small runs (and IMO a better material to use). My last 7.5" travel 4-bar steel frame only weighs 5.25 lbs complete with all pivots and links. All steel except for AL rockers.


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## Walt (Jan 23, 2004)

*Wow!*

Got any pictures? Hell, that's lighter than a lot of freakin' hardtail frames! What did you make it from?!?

-Walt



TacoMan said:


> If you re-design the pivots, you can make it from steel which is easier to work with on small runs (and IMO a better material to use). My last 7.5" travel 4-bar steel frame only weighs 5.25 lbs complete with all pivots and links. All steel except for AL rockers.


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## Kyle88 (May 30, 2007)

pvd said:


> Ha! If you are designing around a specific tube, you should be holding it in your hand. Lots of tubes are listed by Easton, Nova, and Fairing, but most of them are not available or are only available in large quantities. The stuff that is, sucks.
> 
> Your design is just a simple swingarm circa 1990. If you didn't like the Blur, your going to hate this. It's also not finished. You have done none of the hard work, just some main tubes. The pivots are not detailed, the bosses not present, the shock not included, no wheelpath, wheel rate, or spring calculations. Basically, you have a paper napkin sketch.
> 
> ...


Ouch It sounds like engineers are not liked or I'd go so far as to say hated in this forum (PVD)?

I'm with you Jason. I also want to "napkin sketch" my ideas in Pro/E then do the FEA in Pro/Mechanica (including behavioral modeling to optimize the design). I have a old college roommate that works at GM on automotive suspensions. He has a lot of knowledge and a lot of "fancy napkins" that they use up there to do the analysis (although he is just a engineer). I probably won't ever make my frame, but I just enjoy working out the details. If you make it or not I think it's cool that you like the sport enough to even explore it. Working out the details for a full suspension bike is a huge task. Doing it right and really spending the time and finding the perfect solution is very rewarding. I also have some friends at NSK that could hook you up with free bearings (I mean sample bearings) if you find one or two you like.

I'm not trying to start a fight, I just think it's not fair to jump him for trying. I completely respect everyone that has welded up some of the sweet frames I've seen on here. I'm well aware that what works on my tube might not always work in real life, but that goes both ways. We might see something sweet that we can do on screen that someone might not think of with the tubes in hand.

Good luck!
Kyle
(Mechanical Engineer - 8 years product development)


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## MMcG (Jul 7, 2003)

Walt said:


> Got any pictures? Hell, that's lighter than a lot of freakin' hardtail frames! What did you make it from?!?
> 
> -Walt


Yeah - sounds amazing - let's see some pictures.

I keep clicking on your link to the Lunar web site only to find nothing.


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## TacoMan (Apr 18, 2007)

I will be updating the site soon. Right now I am finishing up this new 26" dirt jump frame that I'm building for a local bike shop. It is super stiff, strong, and light. Built for 190-250 pound riders.

The 5.25 lb 7.5" travel frame is what I currently ride. It works really well and I will be building a production version of it once the dirt jump frame is finished. I am only changing some of the details of the chainstay/seatstay to run 135mm wheels and use a 1.125 headtube. My current bike uses 150mm hubs and cranks and a 1.5" headtube, so the production frame may be a little lighter. It uses a super-therm DT with a mix of other tubes to complete it. The rear suspension design is unique and works even better than I hoped for, so I'm excited to get other people to try one out.

This is the picture I posted in another headtube thread, all I have for now.
https://forums.mtbr.com/showthread.php?t=374032


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## Walt (Jan 23, 2004)

*Cool.*

Supertherm isn't light stuff at all, so I'm extra curious now to see the rear end. I could see doing a ~3.5-4# front triangle if it was pretty small out of ST, but that would leave the rear end weighing only 1.5# - which I just can't imagine, especially if it's running on bearings.

I mean, my single pivot DH frames, which are admittedly pretty overbuilt, are 8-10#, and they use supertherm and ox platinum for the entire front triangle. As I recall, the front triangles are 5-6# of that.

As an aside, it's good to see people building long travel bikes from steel. IMO, it's a great app for the material, because it's very strong and easy to repair if done right. Never saw the point of using AL on bikes that are going to see a lot of abuse, myself. I've seen way too many cracked AL DH bikes. Then again, most people buy a new DH ride every year or two anyway, so I guess it's not that important. I plan to be riding my steel long-travel bikes for the next 20 years.

Please do post some more pics when you get a chance. I think there would be a lot of interest (and free advertising...natch)

-Walt



TacoMan said:


> I will be updating the site soon. Right now I am finishing up this new 26" dirt jump frame that I'm building for a local bike shop. It is super stiff, strong, and light. Built for 190-250 pound riders.
> 
> The 5.25 lb 7.5" travel frame is what I currently ride. It works really well and I will be building a production version of it once the dirt jump frame is finished. I am only changing some of the details of the chainstay/seatstay to run 135mm wheels and use a 1.125 headtube. My current bike uses 150mm hubs and cranks and a 1.5" headtube, so the production frame may be a little lighter. It uses a super-therm DT with a mix of other tubes to complete it. The rear suspension design is unique and works even better than I hoped for, so I'm excited to get other people to try one out.
> 
> ...


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## BrendanC (Aug 11, 2005)

my interest: piqued.
Even when I was working for a major manufacturer- with better resources than I have- our lightest 4" travel bike weighed 4.9lbs... and that was built with some seriously thin aluminum tubes!


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## Evil4bc (Apr 13, 2004)

Walt said:


> Supertherm isn't light stuff at all, so I'm extra curious now to see the rear end. I could see doing a ~3.5-4# front triangle if it was pretty small out of ST, but that would leave the rear end weighing only 1.5# - which I just can't imagine, especially if it's running on bearings.
> 
> I mean, my single pivot DH frames, which are admittedly pretty overbuilt, are 8-10#, and they use supertherm and ox platinum for the entire front triangle. As I recall, the front triangles are 5-6# of that.
> 
> ...


Walt

You totally lost me with the # refrances , wre these tube thickness or O.D. ??


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## BrendanC (Aug 11, 2005)

*always late to the party*



Walt said:


> Check Fairing Industrial (www.fairing.com) - they supply some decent stuff in 7075 that might work (PVD, have you seen this?). For example:
> http://fairing.com/bicycle_frame_depot.asp?subcat=a76
> http://fairing.com/bicycle_frame_depot.asp?subcat=a76&subButtedTube=bsp
> 
> ...


I order Aluminum from Fairing regularly, and use it in some of my main tubes. Small quantities are ok.


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## Walt (Jan 23, 2004)

*Weight...*

Number references were to weight, in pounds. Supertherm is mostly 1mm/.7mm/1mm as far as I know. The TT pricelist has it in sizes from 35-44.5mm diameter, 585-700mm length. Lighter and stronger than using straightgauge 4130, but definitely not light in comparision to most other butted tubing. They also have a straightgauge (BMX) seat tube and some straightgauge stays in relatively thick wall.

Does that make sense?

Edit: Just weighed a ST tubeset with a butted 28.6 cromoly seat tube, 100mmx1.2mm OX platinum head tube, and relieved 68mm Paragon shell, and it's 3.7#. Probably subtract a bit for mitering the tubes, then add some for brazeons and paint, plus weld rod and minimal shock mounting material, and you're probably at around 4 pounds for the front end. Not lightweight stuff, particularly.

-Walt



Evil4bc said:


> Walt
> 
> You totally lost me with the # refrances , wre these tube thickness or O.D. ??


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## MichauxYeti (Nov 10, 2005)

JCRacing, go take a test ride on a Yeti. The ASR is 3.7" travel, the 575 is 5.7" travel, and the Seven is 7" travel. They all use a pivot arrangement very similar to your fancy napkin sketch. No Yeti dealers around? Try a Trek dealer. They also use a simple swingarm with a linkage driven shock on their '07 and older Fuel line.


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## Ultra Magnus (Jan 13, 2004)

JCRacing said:


> Walt, and all, here is a picture of my design thus far, (hopefully it attached, sorry, I am new to this). You will notice the drop outs...they are designed to accept the Rockshox Maxle 12mm rear through axle. Obviously I have my work cut out for me on the rear end, hence the reason I posted this thread. I would like to find people who have done what I am doing and get some suggestions, cretiques, etc. Oh, and the tubing I selected thus far is all Easton.
> 
> To answer some of the comments about my post, yes, I am an ME, working full time now in the aerospace industry and also share the passion to design and build my own frame. What forced me into this was I actually bought a SC Blur and was not as impressed as I thought I would be. The Blur is now my wife's bike. I looked into a multitude of different rear suspension designs and read a lot of articles/reviews about the different designs. I just could not bring myself to spend $2,000 on a frame. I would prefer to spend the $2K on a tig welder that I will have for the rest of my life and build my own, even though I know I will spend over $2K, at least I will have more than a frame to say for it, and dramatically increased knowledge from designing it and more respect for the finished product, even if it doesn't turn out the way I hope.
> 
> ...


Here's a frame I designed. The original intention was a DH bike, but the entire frame is driven by a master layout sketch, then all the tubes were designed "in-context". I can change any of the geometry and all the tubes automatically update (and yes, each tube is it's own part file, I don't design uni-solid frames), so it can be manipulated for a short travel XC bike. Within reason though, you can easily invalidate geomtetry if you try to change too much, too fast. The shock mount location also automatically updates. I modeled it after a home build DH bike I saw over on Ridemonkey... (pic also attached)

BM


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## onetonoffun (Jun 18, 2004)

How about some of these for a fs setup...???
http://ahrensbicycles.com/Frame-Components.htm


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## Feldybikes (Feb 17, 2004)

bmadau said:


> Here's a frame I designed...


BM,

Unless you're running a *really* small chainring, your chain is going to run into the right side of the swingarm. You need to elevate it more. Try to look through to the right side of the bike picture you posted. Or check out a Bullit. The DO probably needs to drop down, too. I learned that last lesson the hard way. Otherwise looks nice & simple.


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## Walt (Jan 23, 2004)

*Ah, Chilean DH!*

Majin is a very professional Chilean builder, not a "homebuild" at all, there.

Single pivots rule.

-Walt



bmadau said:


> I modeled it after a home build DH bike I saw over on Ridemonkey... (pic also attached)
> 
> BM


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## Ultra Magnus (Jan 13, 2004)

Walt said:


> Majin is a very professional Chilean builder, not a "homebuild" at all, there.
> 
> Single pivots rule.
> 
> -Walt


I didn't mean any disrespect. That bike came up in a home build DH bike thread over on RM, hell if I can find it again. If I'm not mistaken, he was selling them wicked cheap, I think $400-ish shipped to US? I love the simplicity of the design, no over-done hydroformed/cnc/forged mess that you get from the big bike brands. KISS at it's finest. I especially like the brake caliper mount. And most definitely, if I were to set out to build my own DH bike, without a doubt I'd build a single pivot. 4 bars are great, but there are far too many variables to work out.



Feldybikes said:


> Unless you're running a *really* small chainring, your chain is going to run into the right side of the swingarm. You need to elevate it more. Try to look through to the right side of the bike picture you posted. Or check out a Bullit. The DO probably needs to drop down, too. I learned that last lesson the hard way. Otherwise looks nice & simple.


It's not meant to be a build-able design off of what I've done. I don't have chainguide mounts on the BB shell, nor do I have derailuer mount or disk brake caliber mounts. I'm also sure the chainstays would most likely need to be dimpled or bent inwards a bit for crank/foot clearance. I have no idea where to put the pivot. If I were to actually build it, I'd find a good single pivot bike and borrow its pivot location.

It was more of an exercise in modeling techniques. I could edit the geometry in the master sketch and then watch the model update all the parts with one press of a button. It could probably even be tweaked into XC bike geometry, but a steel FS XC bike would most likely be quite heavy.

BM


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## Feldybikes (Feb 17, 2004)

bmadau said:


> It's not meant to be a build-able design off of what I've done.... If I were to actually build it, I'd find a good single pivot bike and borrow its pivot location.


Check. IME, the hardest thing about starting to make a suspension design is making all the moving parts clear each other. I s'pose that figuring out where the pivots go and all that starts to become harder the more sophisticated you make it.


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## TacoMan (Apr 18, 2007)

Your drawing should work better than the bike in the picture -as far as pedaling that is. The fisrt suspension frame I built, in 1989, had a high pivot location up on the DT like that. It bobbed like crazy when pedaling. Never rode it more than a few tests before I went back to the drawing board and designed a 4-bar that barely bobbed at all. Unless you run a stiff spring with hardly any sag, it is not going to be fun to hammer on the pedals. But your drawing has the pivot closer to the large chainring, so it should pedal ok there, in a granny gear it will bob more.


As for weight, no reason a suspension frame needs to weigh much more than a hardtail. The key is to design the pivots to use the least amount of excess material -that means no 1/4" thick plates, everything needs to be hollow for strength and light weight. Only reason I don't want to show details of the rear suspension is because it is unique and works well and don't need a bunch of copycats. I will wait until we have them ready to produce. This frame does indeed weigh 5.25lb and is very strong and stiff. I weigh 220 and ride very hard. It was not built to be a light bike, but rather a strong bike that is not heavy. Total build weight is 36lb with 2.5 tires, Saint 150mm cranks, FOX 40 fork, FOX 3" Vanilla shock w/steel spring, OS handlebar, and a custom-made steel seat post.


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## heeler (Feb 13, 2004)

> ...As for weight, no reason a suspension frame needs to weigh much more than a hardtail....


Do tell, I actually thought that they do indeed need to be heavier to necissitate the equipment required to make them FS...what about the shock, and the pivots that you talked about making lighter(that hardtail frames don't require). While I have seen some damn light FS frames (Scott Spark)...I don't think this statement is in general true.


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## Citizen Kane (Aug 12, 2007)

Due to a lack of suitable pencils and paper I decided to build my full suspension frame with the tried and tested "make it up as you go along" technique.

Recipe,

Locate three old steel bikes, one mountain style bike, one old fillet brazed road bike and one kids bike.

Ask around, its suprising what sort of old rubbish poeple hold onto and are willing to donate.

Start cutting and shutting. I would thoroughly recomend the use of the Mig for this, think of the process as liquid metal filler no need for endless filing as long as the tube is within an 1/8" of its mating tube its good to weld.

Voila one full suspension bike.

Does it handle well, no of course not.
Does it suffer from pedal induced bob, you bet.
Has is snapped in half, not yet.

This was built about 3 years ago, its now been donated to another family. It was a huge amount of fun to build and even more fun to ride. Just have a go and enjoy.


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## Walt (Jan 23, 2004)

*Best post ever!*

That is the best full suspension home build I've ever seen, and it's got an actual practical purpose. Good on ya!

-Walt


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## rdhfreethought (Aug 12, 2006)

+1

I like how you make the kid push the big ring, slave driver!


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## Bromine (Dec 28, 2007)

Very cool design. I like the use of two chains and the adjustable shock mount. 

It's not very practical as a mountain bike, but looks good as a "tandem"...now to get the stoker cranks high enough for a toddler to pedal.


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## BrendanC (Aug 11, 2005)

Excellent! 
...and it looks nice, too.
glad I clicked this thread "one more time" ;-)


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## TacoMan (Apr 18, 2007)

On-One said:


> Do tell, I actually thought that they do indeed need to be heavier to necissitate the equipment required to make them FS...what about the shock, and the pivots that you talked about making lighter(that hardtail frames don't require). While I have seen some damn light FS frames (Scott Spark)...I don't think this statement is in general true.


...As for weight, no reason a suspension frame needs to weigh much more than a hardtail....

Re-read what I said. It does not have to weigh "much" more. I'm not talking about the weight of the added shock -that is a variable and in my case about 3 lbs extra. I'm talking about the frame only. The pivots do not add pounds to a frame, they add a fraction of a pound to a frame unless someone fell off their designing stool.

This is also not comparing a downhill bike to a trail bike, this is comparing a trail bike to a trail bike. A downhill specific bike would obviously weigh more whether it has suspension or not.

A suspension trail bike can be made from the same tube specs as a hardtail trail bike. The suspension frame will actually see smaller peak loads due to the suspension absorbing the impact spikes. So you may even be able to reduce the tube specs a little. Add in the extra weight of some nicely designed pivots and you now have "a suspension frame that does not weigh much more than a hardtail".


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## knollybikes.com (Jan 8, 2004)

JCRacing said:


> Ok, I have been reading this forum for a few months now and I can't seem to understand why not many frame builders on here are working on a full suspension frame design? Is it just out of most builder's leagues or are most of the people on this forum more into building hard tails? I have been researching different types of rear suspension designs and resently started CADing up a design I would like to persue, but every time I come to this forum in hopes to find other builder's thoughts and ideas on rear suspension design, I only seem to find quotes such as, "stick with a hard tail design." Can someone shed some light on rear suspension design, pivot location, compression rates, bearing selection, etc? Or point me in the right direction for more research on this subject? I am working on a design in SolidWorks that is a four bar linkage system similar to Jamis/Chumba/Nicolai and I would like to find more info on this style suspension design. I am at the point of chosing bearings for the system and I would like to go with IGUS I-Glide bearings...does anyone have any experience with these for full suspension pivots? Any advise would be greatly appreciated!
> Thanks,
> Jason


Hey Jason:

Since my name was mentioned in a post a week ago, I'll give you some information that hopefully will help you out with your project!

Full suspension frames are obviously much more complicated than hardtail frames to both design and build for several (obvious) reasons. Probably the two most important reasons are:


They Require parts more complicated than simple mitered / coped tubes
The geometry changes as the suspension cycles throughout its range of travel

If you are serious about designing and building your own full suspension frame, you will need many skills (which you may or may not already have - of course I don't know you, so I don't know what your background is!) to get your project completed successfully.

First off - I would ensure that you have a thorough understanding of manufacturing. Not just tube work, but also machining including manual mill work, lathe work and probably CNC machining as well if you're going to be serious about your project. Also - it's one thing to borrow a buddy's milling machine, cut out some plates and drill holes into them to make a pair of rocker links, but it's quite another to have access to CNC equipment. You will want this.

Secondly, you need to start your project with a list of goals: what do you want your frame to do? Any good design is all about minimizing compromises. From a performance standpoint, you need to decide what you want your frame to do: is it a trail bike? Do you want to ride smooth trails with it? Do you want to be able to ride technical trails with it? How do you want the rear swing arm to react under braking? What should maintenance be like? What kind of shock do you want to use (and even more importantly, can you get the shock Dyno from the manufacturer so you can design the shock progression rate properly?). What size tires are you going to run and does your design leave good tire clearance? What about the fork - what are you planning to use on the front of the bike?

From a manufacturing point of view, you will have a totally different set of challenges: you will have many constraints to work with: cost, weight, availability of materials, access to manufacturing, access to design tools, etc...

So, I would highly recommend the following advice to make your first full suspension frame project a success!


Get a clear idea of the type of frame you want to build and what you want to do with it.
Have an _extremely clear_ understanding about the basics of frame geometry. You should know exactly what you want your frame to "feel like" and also be able to criticize the frames that you currently ride in terms of what you do and don't like about them. You want to be able to translate your feelings and thoughts into a product - not an easy task. Within two days of riding your prototype you should be 100% confident in your decision of what to keep the same and what to change. Even on a full suspension bike, a half a degree change of head angle and 6mm (1/4") of BB height can make a very noticeable difference.
Fully understand the mechanics of the suspension design: what it's going to do and what it will mean performance wise. There is a TON of BS in advertising in the bike industry: most suspension design ads are blatant lies designed to sell product. Understand the tradeoffs between neutral pedalling and anti-squat. Understand how the rear suspension design will affect brake performance (and how you can use these forces to get your desired result). There are good and bad linkage designs, but the fact of the matter is that a very good suspension bike can be made with even a simple swing arm design. Good full suspension frame design is about 25-50% due to the suspension design used and its implementation: the rest is due to geometry and a bunch of other characteristics that are less obvious:
Front derailleur implementation - often overlooked and highly critical
Tire clearance
Lateral stiffness
Good chain line
Braking effects on suspension
Serviceability and maintenance
Reliability
Features (can you raise and lower the seat enough, can you put a water bottle on the frame, do you have reasonable stand over height, etc...)

Keep the designs simple at the start - that doesn't necessarily mean unsophisticated - but ensure that they are easy to make for your first prototype(s). This means that you should probably use commonly available tubes: I would strongly recommend 6061 aluminum as it's available in a huge array of shapes and sizes. You'd be surprised: you can make a very strong, durable and reasonably light frame from regular straight gauge 6061 aluminum tubing. Believe it or not, but most of the fancy down tubes now popping up in the industry (the ones that are bent where they meet the headtube) are designed NOT for strength, but for reducing manufacturing costs. If you can bend a tube, then you don't have to weld a gusset underneath it. This removes a part (the gusset) and a few processes (drilling breath holes in the down tube / head tube, pre-welding the underside of the down tube, and welding the gusset onto the underside of the down tube) and chops several dollars out of the overall manufacturing costs.
Understand the costs involved. Make an estimate then multiply it by 4 or 5. That should be pretty close 
Forget about FEA: sure, it sounds cool to say that you "fully FEA'd your design" and it's neat to print out pretty pictures of Von Mises yield stresses, but good designing is a combination of experience and fundamental understanding. No amount of FEA can fix a crappy design. FEA is best used in certain situations to optimize designs, not to create them from scratch. overbuild your first design, beat the living crap out of it, and _then_ once you're happy with all the main details, you can start looking at ways to tweak the design.
Expect to make mistakes - your first prototype will certainly be cool as it's your first bike, but your second prototype should ride a hell of a lot better!
And most importantly: DON'T BUILD YOUR FIRST DESIGN!!! It sounds like you have CAD experience: fully model up your bike (bmadau's suggestion about using a master sketch is an excellent one and that is exactly what most manufacturers do) and then put it aside for a bit. Show your friends and get their input on it. I can definitely let you know that if Knolly built the first frames that I fully designed, we would never have gotten started as a company. It was cool to have a full design modeled up in CAD, but they were completely unpractical designs! However they were also highly evolutionary and in a way helped me figure out a lot of problems with conventional designs and lead to the frames that we're now manufacturing.

Anyway, just some pointers. I have personally seen about half a dozen home made full suspension frames: some have been simple and some have been WAY overly complicated. Almost all were built by mechanical engineering students: mainly because they had access to both CAD software and also cheap (i.e. free to use) university machine shops who could make the parts that they needed. However, almost all of the designs were also not fully thought out mainly due to the fact that the frames were done as a project / thesis for a class and hence had a time restriction on them.

Don't be in a rush to build your bike. Like I said, try to FULLY understand everything about suspension design and frame manufacturing: you should know the pros and cons of every design on the market (and especially the one that you plan to use) and believe me, all the "most advertised, best purported suspension designs" ALL have compromises in them. Even the best design can be totally ruined by poor implementation.

On the flip side, look at bikes built by Ventana and Turner: they are both linkage actuated single pivot designs, yet both companies have cult like followings of hyper loyal customers. This is because the _overall_ designs of these frames have been highly developed over many years. They will far outperform the newest, most hyped counter rotating linkage blah blah blah because the rest of the package (geometry, manufacturing, customer support, etc...) has also been designed to a very high level instead of being slapped together to meet the next model year's production time line.

There is no free lunch, but if you do your homework you can make a very successful project out of this. AND, that is something that all the internet arm chair engineers in the world can never take away from you. All of their talk is just talk - if you DO, then you will have an understanding far beyond what ANY of them have.

Good luck and let us know how it works out!

Oh ya - PS: igus is a high quality product and you will find it used on several higher end manufacturers' products. However, you should be sure that you know WHY you want to use igus as opposed to a ball bearing system. Both have their advantages and disadvantages. In terms of igus, it would be best to get a catalog from them (or go to their website) to understand the characteristics of the different products that they offer and how to properly integrate them into your design.


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## mobile chernobyl (Apr 12, 2006)

^ to Knolly

A Q on Igus, 

I'm particularly interested in the iglide Q series as they have outstanding specs in area of rear suspension. They are recomended for low heat conditions seeing oscillating, high loads with shock and impact loads, and offering the added benefit of low friction. Sounds like rear suspension to me. A side note, in some other research, and through some college prof's recommending - the iglide Q is very popular in college SAE competitions right now, for exactly the same use - Suspension. pretty much everyone is using 4 bar linkages now, and having great results with the Q. 

I have a design (blah blah, who doesnt) and I am currently having interference issues currently only with the main pivot and rocker linkage (single pivot design). I found on their catologue a 12X14X20mm flanged bushing. I guess its not much of a question but what would you think of using 2 of these (both sides) for the main pivot on a single pivot/linkage driven design, and do you have any contacts of anyone currently using the Q series in the bike industry. It always seams that the bikes should use bushings (oscillating) instead of bearings (rotating) but it is never that way... any reasons (i know they develope slop, but that was old crappy brass bushings, now theres DU and iGlide)? haha.


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## Ultra Magnus (Jan 13, 2004)

No matter how low friction they say igus bushings are, they are still a lot higher than a roller bearing, that's for sure. It's common knowledge that roller bearings don't do well in low rotation high load applications, but they are over built enough to make them work in bike frames. 

BM


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## JCRacing (Dec 20, 2007)

*Igus*

Mobile C, if you haven't already seen it on the IGUS website, check out this link. This guy used them to rebuild his Jamis rear suspension. I have a full catelog and samples being sent to me, you should do the same. Yes, the first I heard about IGUS was in Mini Baja in College, they are very popular with the SAE teams. Keep me posted!

http://www.igus.com/applicationcorner/customertestimonials/independentcustomer.asp

Jason



mobile chernobyl said:


> ^ to Knolly
> 
> A Q on Igus,
> 
> ...


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## mobile chernobyl (Apr 12, 2006)

*JCRacing* - Thanks for the link. Interesting they used J series and not Q. They would know best however, and I can still get the 12X14X20mm size in either J or Q, might as well get it in both haha. J seems to be more resistant to chemicals, however J seems to have a longer static to kinetic friction threshold (from .25 to .1) and a higher overall kinetic coef. Not sure if thats the best thing for a low speed oscillating system like the bicycle, Odd they spec'd them instead of the Q series. 
-The samples and catologue were shipped to you by request? did you have to pay shipping or anything or is it their incentive to ship it to you free?

*bmadau* - I'm aware of the fact that bearings will have lower friction, I guess i'm interested in whos utilizing the new synthetic materials for bushing use in the bicycle suspension industry.


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## JCRacing (Dec 20, 2007)

Noel,

First of all, thank you so much for your recommendations, suggestions and words of encouragement, it is greatly appreciated! I am sure I will use your post as a reference as I continue with my design and on into the build. To be honest, I had never heard of Knolly bikes and I just went to the website to see what you build. I am impressed, and I really respect the fact that you took the time and effort to read through my silly post and offered your suggestions. As the one behind Knolly bikes, for you to do something like that is really cool! So thank you again!

To answer some of your questions and comment back to some of your comments, I posted my background in one of the previous posts, so you can check that out if you'd like. The intent of this frame is to be an All Mountain frame that will have between 6"-7" of rear travel and will be mated to the Fox Talas RC2 36 160mm travel fork. As I mentioned in an earlier post, I recently purchased a Santa Cruz Blur LT, (primarily because of all the hype...yes I fell into the hype trap), but in my opinion, I felt as though the bike had a serious case of brake jack and it left me beggin for my hard tail! I was not as impressed with the bike as I had hoped for going down rough terrain; however the bike does pedal extremely well. I started doing some research on different types of rear suspension and that's when I realized that the experience I was having on my Blur was brake jack and I wanted to eliminate this with my design, even if it sacrifices some pedaling capability. In other words, I would sacrifice the climb for a better, more predictable descent. A comment on the shock, this is something I was thinking about as well, how do I obtain the dyno of the shock I would like to use, (Fox DHX5.0 coil)? I am going to try calling fox to find out if they will give me this info of an off the shelf shock, but I know you can revalve the shocks, etc. When I put my design through the CosmosMotion analysis, I can assign damping and spring constants on the shock. I will need these values to do it. I am hoping Fox can get me pointed in the right direction for this. My goal is to have adequate tire clearance for 2.5" rear max.

Do you or anyone else have any articles that you recommend I read on suspension design, etc? I have found a few really good articles on brake jack, etc that are good, (thanks to PVD's wiki!!), but are there any that are a must see that you can think of? As you said, I really want to research as much as I can into the different types of suspension so I have a better understanding of it as a whole. I have already learned so much in the last 3-4 weeks and I know I am not even scratching the surface! Any links, etc. that you could recommend would be greatly appreciated!

Thank you all for your comments/suggestions, even criticism, that's what really gives me the drive to do it! I'll post more pics on here as the design progresses.

Jason



knollybikes.com said:


> Hey Jason:
> 
> Since my name was mentioned in a post a week ago, I'll give you some information that hopefully will help you out with your project!
> 
> ...


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## JCRacing (Dec 20, 2007)

I had the catelog and samples sent to my work, I am using some IGUS bearings on a project for work, but also want to use them in my design. They just arrived today. You can go online and order it up, it'll be at your place in about 7 days, free of charge.

Jason



mobile chernobyl said:


> *JCRacing* - Thanks for the link. Interesting they used J series and not Q. They would know best however, and I can still get the 12X14X20mm size in either J or Q, might as well get it in both haha. J seems to be more resistant to chemicals, however J seems to have a longer static to kinetic friction threshold (from .25 to .1) and a higher overall kinetic coef. Not sure if thats the best thing for a low speed oscillating system like the bicycle, Odd they spec'd them instead of the Q series.
> -The samples and catologue were shipped to you by request? did you have to pay shipping or anything or is it their incentive to ship it to you free?
> 
> *bmadau* - I'm aware of the fact that bearings will have lower friction, I guess i'm interested in whos utilizing the new synthetic materials for bushing use in the bicycle suspension industry.


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## derby (Jan 12, 2004)

*Seat time is everything*

RC Racing - I applaud you for wanting to build your own suspension bike. Very few have the ambition, aptitude, and skills to do so.

You seem to be asking for references on bike suspension design theory as well as tips on materials and pivots. There are many half-baked theories floating around and very much sales hype even some big lies. I've even cooked or kooked?  up one or two of my own theories over the last 10 years while I've been researching why some suspension bikes ride noticeably much better than others - for me.

The key is how you want the bike to ride for yourself. Even the most popular bike manufacturers have a limited following. Some riders like how some brand-X rides, others just prefer the ride, or more simply the look or rider culture of some other brand.

And the only way to know is to test ride a wide variety of designs and similar designs by various builders. Also ride a wide variety of trails to get a feel for the differences in traction and handling over various designs.

I suggest you plan a long vacation with a plan to test ride as many bikes as possible. Call the manufacturers ahead of time and get references for dealer demos lined up. This is most revealing of the differences in design, every bike feels different, and you can note and measure what the design differences are. In California the Sea Otter Classic bicycle event that's coming up in mid April is a great place to demo many designs over a 4 day event and see and participate in some great racing from the first time racer classes to world champion pros.

Good luck with your project!


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## JCRacing (Dec 20, 2007)

Derby,

Great suggestion, I have ridden a lot of different full suspension bikes, but it looks like the Sea Otter Classic would be the place to go to really see a large variety of designs in one place! It's about 4 hours from me, I'll try to make it happen! Not sure if I can make it the whole time, but maybe for Saturday and Sunday. Thanks for the post on this, I had never heard of the event!

Jason



derby said:


> RC Racing - I applaud you for wanting to build your own suspension bike. Very few have the ambition, aptitude, and skills to do so.
> 
> You seem to be asking for references on bike suspension design theory as well as tips on materials and pivots. There are many half-baked theories floating around and very much sales hype even some big lies. I've even cooked or kooked?  up one or two of my own theories over the last 10 years while I've been researching why some suspension bikes ride noticeably much better than others - for me.
> 
> ...


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## knollybikes.com (Jan 8, 2004)

Hey Jason:

No worries on the reply - happy to help!

In terms of your other questions, I can probably help a bit, but really it's going to come down to you doing the research.

One thing that you definitely should understand is that there are three main characteristics that most suspension designers are going to be looking at when designing suspension:


*Pedal induced suspension movement (i.e. pedal bob)*
*Suspension induced pedal movement (i.e. pedal feed back)*
*Rear brake / suspension interaction (i.e. brake squat or brake jack)/*

Those are kind of the three most important parameters in the "overall design" that must be tweaked in your design. Of course everyone wants to eliminate 1, 2 and wants to tune #3 to what they think is appropriate for the given terrain.

The first thing to do is to understand each of these effects: Number one (*Pedal induced suspension movement (i.e. pedal bob)*) is probably the most complex, as you are dealing with at least three forces:


The first force is the tension on the chain when you push on the pedals. If the chain tension is not perpendicular to the tangent of the wheel path, then the chain tension will give a vector force to the rear hub, causing the rear wheel (and hence rear suspension) to want to either extend or compress.

The second force is the acceleration of the rider / bike: as you know, when you drive your car and step on the gas the front of the car will "lift up" and the rear end will squat down. When you hit the brakes hard, the opposite happens. This is because the forces of acceleration / deceleration are between the tire and the pavement, however the car's center of mass is _above_ the pavement - by about 18-24". A bicycle is the same situation, except even worse because the wheelbase is much shorter and the center of mass is much higher. Hence, when you pedal, you are "accelerating" the frame. Even if you're just maintaining speed, you're actually "micro-accelerating" the frame because every pedal stroke is overcoming the forces of friction that are working to slow down the bike. Every time you accelerate the frame, you're causing the wheels to move forward, while the frame / rider want to slow down and relatively move backwards. This causes the rear suspension to compress (squat) and the front suspension to unload (extend).
The third force is that the center of mass is moving up and down as you pedal. If you've ever seen someone who is really bad at pedaling "Square", you'll know what I mean. The mass in their legs is going up and down and they are almost "hopping' the bike as they pedal. You can pedal smoother (i.e. more "round") and reduce this quite a bit, but it's pretty much impossible to eliminate this and very hard to pedal round when doing out of the saddle efforts like when sprinting or when tackling technical climbs.

What so called anti-squat designs try and do is use a variable chain stay length to counteract compression of the rear suspension under pedaling effort.

Having a chain stay length that shortens as the suspension is compressed is generally not good because compressing the rear shock absorber uses power. This makes the bike's pedaling feel "mushy" and not responsive.

If the chain stay length grows as the rear wheel is compressed, tension on the chain will try and "shorten" the chain stay length and hence try and extend the rear suspension. Causing it to extend can stiffen up the frame under pedaling and make it feel like a good pedaling bike. This is great for smooth trails, but if you do this on technical trails (where essentially the terrain is going to "hit back" against the rear wheel, then the suspension will start to kick back - i.e. want to rotate the pedals backwards, against the direction that you're pedaling. This is because every time the terrain "hits" the rear wheel, you're lengthening the chain stay. Because the free hub body can only idle in a backwards rotation (when you're coasting), the increase in chain stay length means that the chain will essentially get pulled backwards, wanting to rotate the cranks backwards. This is the trade off to using chain tension as an "anti-squat" force.

The issues is that using anti-squat (chain tension) to help fight number 1, you increase the likelihood that the rider will start noticing #2, *Suspension induced pedal movement (i.e. pedal feed back)*. Of course, the worst case is when climbing in the granny gear because a certain length of chain stay growth translates into a much larger "rotation angle backwards" of the crank arms compared to a larger chain ring. I.e. if the bike had the following chain ring sizes: 22, 33 and 44 tooth, the kick back would be twice as bad in the granny gear as in the big ring; the middle ring would be 50% worse than the big ring. This is why frames that feel like they pedal great on fire road climbs can be poor climbers on technical terrain.

So a good suspension design has to find a nice balance between the two tradeoffs and might tailor these characteristics any particular way depending upon what they want to do.

*Brake interaction* is kind of separate because essentially you want the bike to either be more or less neutral or the suspension to compress under braking. You never want it to extend, as that makes the bike feel like it's going to pitch the rider over the front of the bike! There are varying opinions on how much brake squat (if any) is necessary / desirable. Typically, a bit is nice to offset fork dive in steep / technical terrain, but too much causes the rear shock to become partially compressed (effectively pre-loaded) and makes it much more difficult for the rear suspension to be supple and sensitive to smaller trail features (a common complaint of single pivot designs).

Also, derby's post above is bang on. No one design is best for every rider. Also, as I mentioned before, the suspension is only _part_ of the overall frame design. There are many other elements that haven't been talked about such as shock progression, frame geometry, and so many other factors.

Hope this helps!

Cheers,

Noel



JCRacing said:


> Noel,
> 
> First of all, thank you so much for your recommendations, suggestions and words of encouragement, it is greatly appreciated! I am sure I will use your post as a reference as I continue with my design and on into the build. To be honest, I had never heard of Knolly bikes and I just went to the website to see what you build. I am impressed, and I really respect the fact that you took the time and effort to read through my silly post and offered your suggestions. As the one behind Knolly bikes, for you to do something like that is really cool! So thank you again!
> 
> ...


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## dr.welby (Jan 6, 2004)

knollybikes.com said:


> The first thing to do is to understand each of these effects: Number one (*Pedal induced suspension movement (i.e. pedal bob)*) is probably the most complex, as you are dealing with at least three forces:


Great list Noel. I'll add a fourth force - swingarm geometry can also be used to create anti-squat. Think of it this way - let's say you had a bike with a really, really high pivot. Obviously your chain tension would pull the swingarm forwards and jack up the back end of the bike. But even without a chain - say you had little Wile E Coyote rockets zip tied around you rim and than turned the wheel. As the wheel pushes forward it against the rest of the bike also would make that swingarm extend and jack up the rear suspension.


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## Thylacine (Feb 29, 2004)

TacoMan said:


> If you re-design the pivots, you can make it from steel which is easier to work with on small runs (and IMO a better material to use). My last 7.5" travel 4-bar steel frame only weighs 5.25 lbs complete with all pivots and links. All steel except for AL rockers.


Still waiting for pix of this amazing sounding bike. Got pix or are you doing some big reveal for the press of something?


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## brant (Jan 6, 2004)

dr.welby said:


> Great list Noel. I'll add a fourth force - swingarm geometry can also be used to create anti-squat. Think of it this way - let's say you had a bike with a really, really high pivot. Obviously your chain tension would pull the swingarm forwards and jack up the back end of the bike. But even without a chain - say you had little Wile E Coyote rockets zip tied around you rim and than turned the wheel. As the wheel pushes forward it against the rest of the bike also would make that swingarm extend and jack up the rear suspension.


Aligning tyre thrust force relative to the main pivot...

Yeah - that's one thing that's puzzled me about many 29er suspension bikes - in that the pivot seems to be located in the same place relative to the BB, but the wheel centre is 1.5in higher.


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## Ultra Magnus (Jan 13, 2004)

mobile chernobyl said:


> *bmadau* - I'm aware of the fact that bearings will have lower friction, I guess i'm interested in whos utilizing the new synthetic materials for bushing use in the bicycle suspension industry.


Progressive suspension used hte G material for years on the 5th coils. Worked wonderfully. They have enough ealsicity to move around wiht frame/pin flex (high edge load conditions) without any damage. That and the homogeneous material is great since you don't just have a thin .003" thick layer of low friction coating as in a DU bushing, which is what they previously used. Once it wore off, serious pin damage would occurr, bad clunking, etc, and only after a few hours of riding. We went from an epidemic of DU failures to never hearing of any eyelet bushing failures overnight.

BM


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## derby (Jan 12, 2004)

JCRacing said:


> Derby,
> 
> Great suggestion, I have ridden a lot of different full suspension bikes, but it looks like the Sea Otter Classic would be the place to go to really see a large variety of designs in one place! It's about 4 hours from me, I'll try to make it happen! Not sure if I can make it the whole time, but maybe for Saturday and Sunday. Thanks for the post on this, I had never heard of the event!
> 
> Jason


The Sea Otter is amazing, like a 6 ring circus of bike racing and stunters, plus a huge vendor expo. Try to go at least on Friday to demo it's very crowded on the weekend and there's a lot of bike candy and scenery going on to distract. Better book a motel reservation soon it gets very expensive or far out as time approaches. Camping there can be good too but sometimes pretty noisy or rainy. The RV lots are probably packed already.
:thumbsup: :thumbsup:


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## mobile chernobyl (Apr 12, 2006)

bmadau said:


> Progressive suspension used hte G material for years on the 5th coils. Worked wonderfully. They have enough ealsicity to move around wiht frame/pin flex (high edge load conditions) without any damage. That and the homogeneous material is great since you don't just have a thin .003" thick layer of low friction coating as in a DU bushing, which is what they previously used. Once it wore off, serious pin damage would occurr, bad clunking, etc, and only after a few hours of riding. We went from an epidemic of DU failures to never hearing of any eyelet bushing failures overnight.
> 
> BM


Thanks for the info man! cool stuff. Synthetics are amazing stuff, one of my dad's friends worked with a ceramic coating they would actually apply to the bottem of the space shuttle for re-entry, its crazy some of the chemicals he has left over in his garage haha. I am definatly looking forward to hopefully recieving a sample and more info from igus. I'm actually trying to integrate more bushings into my design, but I def realize where a bushing will work well, and were it will not haha, i've replaced plenty a bearings from four-bars, vpp's and maestro/dw links and its pretty obvious that the high load/low angular oscillation tends to kill the ball bearings. most of the time when they come out they wont rotate until an extremely high load is put on them... or theyre cleaned and reassembled lol


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## Thylacine (Feb 29, 2004)

Turner has been using Igus bushings for over 10 years now Jnr, so don't get too excited.


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## Slyp Dawg (Oct 13, 2007)

this has just furthered some ideas I had about a FS frame. would I be correct in saying that if I somehow managed to make a frame with the main pivot concentric with the bottom bracket, then applied a constant force on the crank (aka getting the correct sized allen bit for a cordless drill, assembling said bit and drill, then sticking the exposed end of the allen bit into the the crank bolt, if there is one, then burying the trigger in the grip of the drill. or something like that) the suspension would do nothing? I know that isn't a 100% accurate representation of the forces that pedaling would create, but it would give me an idea of what would happen on the power stroke. if I used a Cane Creek Double Barrel I could likely tune out other pedal induced bobbing using the low speed compression, but I'm not 100% sure about that. I've got two ideas for a concentric main pivot/BB setup each using bloody huge pivot bearings/bushings and a two piece sleeve that serves as the axle that the swingarm pivots around, then the bottom bracket threads into that, and the only difference between the two designs is where on the sleeve the pivots are located, but what is bugging me the most is shock setup. I can't decide if I want a shorter chainstay length and just use a rocker actuated shock or if I want to use a longer chainstay and mount the shock directly to the chainstay, sort of motocross bike style. the whole thing could be made pretty damn stiff if I use a TA and a rocker to actuate the shock, or if I get the swingarm machined out of billet aluminum, or any combination of those three options. the latter wouldn't exactly be the lightest option out there, but it would work, it would be shiny, and it would be stiff as a teenage boy waking up to a female porn star. bricks of aluminum don't flex under the forces a mtb can exert on them (you'd probably need a hydraulic press to get a brick of aluminum to flex if it wasn't ungodly small in one dimension compared to the other two (thickness compared to length and width, etc)) and neither does bricks of aluminum that have been machined down and have a 12mm through axle going through them at one end and two gigantic pivots (as in, noticeably larger than the common bottom bracket) at the other end
a lot of the above is just my mind wandering a bit before the local animal control comes after it, but some of the ideas might be of some use to someone who has more access to machines and CAD programs than I do


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## Thylacine (Feb 29, 2004)

Problem with a concentric pivot is that there is nothing countering the chain loads, so it's sensitive to any torque variations (ie: the sad excuse for cadence we call 'pedaling') and will bob like a mutha. You'd solely be relying on shock platform to counter it.

The second issue is axle path, which almost instantly arcs forwards which is way less than desirable for a multitude of reasons.

Still, I'm a complete know-nothing and other companies still persist with or have reintroduced the design, so -


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## dr.welby (Jan 6, 2004)

Slyp Dawg said:


> this has just furthered some ideas I had about a FS frame. would I be correct in saying that if I somehow managed to make a frame with the main pivot concentric with the bottom bracket, then applied a constant force on the crank (aka getting the correct sized allen bit for a cordless drill, assembling said bit and drill, then sticking the exposed end of the allen bit into the the crank bolt, if there is one, then burying the trigger in the grip of the drill. or something like that) the suspension would do nothing?


Nope. It will compress the suspension. And dynamically it will be even worse since there's so little anti-squat with that pivot location.

But if you want to try it, take a look at the Lenz and Cove bikes, and at the Kona A singlespeed.


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## Slyp Dawg (Oct 13, 2007)

ah, ok. so when I pedal off on a bike like that, someone watching from the side would be able to watch the suspension squat like a motocross bike with the throttle pegged on a nice grippy surface?


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## knollybikes.com (Jan 8, 2004)

Thylacine said:


> Problem with a concentric pivot is that there is nothing countering the chain loads, so it's sensitive to any torque variations (ie: the sad excuse for cadence we call 'pedaling') and will bob like a mutha. You'd solely be relying on shock platform to counter it.
> 
> The second issue is axle path, which almost instantly arcs forwards which is way less than desirable for a multitude of reasons.
> 
> Still, I'm a complete know-nothing and other companies still persist with or have reintroduced the design, so -


No - not a know-nothing at all - you're pretty much bang on!!!

BB concentric pivots have one advantage - no pedal feed back. However, in my opinion they pay for that advantage dearly by requiring a rear shock with so much low speed compression damping (to eliminate chain tension induced suspension movement) that the bike has no small bump sensitivity.

Cheers!


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## Thylacine (Feb 29, 2004)

knollybikes.com said:


> No - not a know-nothing at all - you're pretty much bang on!!!


I know I am.  Just test driving this 'self deprecation' thing. :thumbsup:


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## Acme54321 (Oct 8, 2003)

Knolly here is a question for you that you might be able to answer.

If some individual did design a FS frame, fully model it and have drawings for parts, ect. Is there any company that can prototype/build the bike for them? If so what kind of costs would you be looking at to have one custom built frame done? I was thinking about this the other day but I kind of doubt there will be anyone out there who would want to prototype a frame without any promise of a production run to follow, and even if there is someone who would be willing to build it I was thinking it would be big money for just one frame. I was also thinking about overseas manufacturers but that brings in a whole new problem.


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## Thylacine (Feb 29, 2004)

I've done this, so perhaps I can answer.

A lot of it depends on cash, yeah. If you've got a heap of money to spend, there are places out there that could do the work from start to finish. I suspect it would cost a bomb.

If you want to do it on the cheap, you really need to do everything that you can yourself. For example, the FS frame I did 7 years ago, I did all the design work and modelling myself, then had a friend do all the CNC work. The front end I got done at a frameshop that specialised in Aluminium, and the rear end I got the tooling made by a subcontrator, got it welded by an aerospace company, heattreated by a local heat treater, painted by a local company, and electrode-less nickeled the swingarm using another subby.

This was the cheapest way to make it happen, and from memory took about 8 months.

You could probably go overseas if you wanted to. Your models and drawings would have to be absolutely meticulous though, and of course there would be some risk with QC, IP etc that you'd have to take into account.


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## Acme54321 (Oct 8, 2003)

Good to know. I figured the overseas thing would be difficult because like you are saying, to make up for physically not being there, you would have to have perfect drawings and whatnot, also a pretty good understanding of the manufacturing capabilities of whoever is making it. That and a pretty simple, straight forward design that pretty much explains itself.

I am a ME student so I have full access to CNC machines and that sort of thing. The issue would really be having it all welded together and heat treated if it was necessary. 

Thylacine, if you don't mind me asking, how much did you end up shelling out for your frame? Obviously it will cost a bit more now than 7 years ago but would be in the ball park.


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## yogiprophet (Jan 9, 2006)

[email protected] said:


> Aligning tyre thrust force relative to the main pivot...
> 
> Yeah - that's one thing that's puzzled me about many 29er suspension bikes - in that the pivot seems to be located in the same place relative to the BB, but the wheel centre is 1.5in higher.


Great observation! I have noticed the same thing. The outcome is less anti-squat and a more forward moving axle path, but then again most 29ers have less suspension to compress.


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

Slyp Dawg said:


> ah, ok. so when I pedal off on a bike like that, someone watching from the side would be able to watch the suspension squat like a motocross bike with the throttle pegged on a nice grippy surface?


Motocross rear suspension stiffens under power. It's a crude system that riders use to their advantage. Although a multi-link would accelerate and brake better over bumps, the manufacturers stick with a simple swingarm because the rider's use of throttle can adjust the stiffness and rebound tendencies of the suspension. Go to a Supercross event; before riders land from a triple, you will hear them get on the throttle. This stiffens the rear suspension for these absurd loads. If the bike were set up stiff enough for the big jumps, it wouldn't work on the rest of the course. And blipping the throttle on take-off causes faster rebound of the rear suspension, allowing a 'boosting' effect for greater air.

Sure, bikes will squat some under acceleration, but not nearly as much as they would without so much built-in anti-squat. They're sorta like an MTB in it's lowest gear.


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## Kyle88 (May 30, 2007)

Shockworks... A Suspension Overview
http://www.mountainbike.com/shockworks/home.html
This is interesting to see. They compress a few bikes and explain how they work.


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## hectorgramosm (Aug 14, 2020)

*Kona warranty deparment*

Hello fellas, just a kick question, has anyone ever had a warranty claim with Kona? I am right now claiming a pair of cracks that appeared on my frame just 2 months after I bought mi bike, I am 5'11' and 160 pounds, decided to go with an M size sience I came from an Intense Tracer 27.5" also M size frame, but the frame is now cracked, they are blaming it on me but the opinion with a couple of dealers that I have encountered is that the frame should resist just fine, I would like to know riders opinions about the topic and about Kona warranty deparment because right now they are making my life really hard! thanks in advance community. I must say the post was always within the limits marked on the dropper by the manufacturer


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