# Pivots: bearings or bushings? DW link vs VPP?



## MDEnvEngr (Mar 11, 2004)

OK, so I'm slipping down this FS slope. After riding rigid or hardtail for the last 15 years I've spent some time on the single pivot I built myself. The FS is fast - it doesn't really even feel like I'm going that fast and then I look at the Strava segments and I see new PRs. Hmm.

Well, the bike I'm riding was my second crack at a FS bike and it has some issues that I want to fix on the next one. And I've been doing some thinking:

It seems to me that a bushing would be better suited for the high frequency back and forth load that a pivot sees. It would be better at supporting the side to side loads. But the bearings sure are touted as an upgrade on the popular production bikes. I have heard of bushings wearing too quickly. I ordered some nice oil-impregnated bronze bushings and they are smooth on my Al shaft - about as smooth as the bearings I just used. I also orderd up some plasitc igus bushings (specifically noted on some manufacturer's PR) and they are nice too. And light, and cheap.

I suppose I ought to just build it and see how it goes and get back to you all on this right?

Now - I'm thinking a multi link suspension next. I don't see it as too much harder than the single pivot, really. There is the links to fabricate - but I can get some AL bar stock and go crazy with the drill and maybe even mill. Don't think that it would work for a fella trying to make a living at this, but that is not my point. 

But my question here is which one - VPP or DW link? According to what I've read the main difference is the orientation of the upper link. The VPP upper link has the pivot on top and swings CCW, the DW upper link has the pivot on the bottom and swings CW. I think the VPP would be easier to fabricate because the shock pivot is on the same shaft as the lower pivot on the upper link - and it's already "inside" the front triangle. The DW upper link is "outside" of the front triangle and some arrangement has to be made to attach the shock to the swingarm. Could be that upper link is also and rocker - but that might be getting beyond what I can fab in the basement.

But I've heard (remember I'm a reformed rigid guy here) that the DW is "better" than the VPP. What's some thoughts on this...

I was considering posting this down the hall in the suspension forum but am reluctant because I've afraid it might start an arguement. But that could be fun too...

Anyway, thanks for any input you might have! Good day - B


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## Walt (Jan 23, 2004)

Bushings will suck bad after a few months. I would not do that if I were you.

Ride some different suspension designs and see what you like. It's really more a matter of feel (and marketing) than of actual objective performance. 

-Walt


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## slowrider (May 15, 2004)

I have two Intense VPP Tracers, a 29r and a 275, along with a Turner Flux DW, As far as ride quality is concerned the 275 has a different progression than either the T29 or the Flux and is not as smooth on the small chatter as the T29 or flux but it eats the bigger stuff better. I think the progression of the individual set up is more important than the DW/VPP question.
Walt is the expert on building bikes but I'll say that my bushing experience with Turner has been flawless, I still own 2 Turners from 2002/3 and the only reason I changed the bushings on the one was because I had the frame powder coated, the other frame is still running the original bushings. My DW flux with 120mm and bushings is as smooth on small chatter as my 140mm T29 with bearings. Just one opinion from the dry Southwest, your results may very.


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## Walt (Jan 23, 2004)

There is a reason the industry has gone away from bushings. They develop lateral play and slop, they stick, etc. Just in general not as functional and reliable as bearings. They are super cheap and light, though, which is why they still occasionally get used for stuff. I think your 15 year old bike is probably the exception (hell, any fully functional FS mountain bike that age is the exception!)

In any case, I've ridden them all and I keep coming back to single pivots, which IMO feel better on small stuff, are simple/light and virtually indestructible, and performance-wise give up nothing (I've tested this going uphill, at least) to more complex designs. 

The feel thing is totally subjective, though. Most people end up liking best whatever design they first rode because full suspension of any kind usually feels awesome coming from a hardtail, and different FS designs will end up feeling weird after getting used to the first one. 

My first was an LTS-team "downhill" (60mm travel!) bike. Not a single pivot! With bushings (which developed a ton of slop immediately)! So there you go, I'm the exception to my own rule.

-Walt


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## MannaDesigns (Mar 5, 2013)

I'm not a "bike engineer" but my day job is around single pin joints in aerospace. Really bushing/bearing depends a lot on the load the joint sees, and the rate of movements. I've seen bushings in bikes in the past, but personally wouldn't go that route. FS bikes are moving so much constantly that it makes a lot of sense to stay with a bearing to me. Now as far as which one... good luck

VPP/DW - maybe not helpful here, but my 2 cents.... I ride a nomad and like it, but many have issues with getting VPP setup correctly (myself being one of them) you really need to have it dialed in to the sag correctly for the suspension to do its thing correctly. I don't know a ton about DW, but have heard good things. I'd suspect any linkage system is going to be similar in setup be critical - so that's not really intended as a downer, more just food for thought. Have you thought about a simple "FSR" style copy? Also, I'm guessing you know about the linkage program? Would likely help you a lot in your layout and figuring out your shock rates. 

Looking forward to see what you come up with!


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## MDEnvEngr (Mar 11, 2004)

Thanks for the input so far! I think I should add here that I think my big motovation for going to a multi link would be to more fully support the swingarm. It seems to me like the single pivot ends up using the shock for support to a certain extent and that can't be a good thing. Even on my most recent with 2 bearings on either side of the main pivot I can still wrench the swingarm side to side a bit. Too much? Who knows! 

Perhaps one of theose scissor-linkages that were referenced in an earlier dually thread would take care of that...


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## Walt (Jan 23, 2004)

Just use a rocker to drive the shock or some other little linkage. Assuming you actually are having a problem with the shock seals or something. If you aren't, don't worry about it. 

-Walt


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## MannaDesigns (Mar 5, 2013)

This would also give you a little more freedom with tuning the shock rate - thats why a lot of the smaller companies were using a "linkage driven single pivot" design before the FSR patent expired... Transition is a good example of that. But I'd also wager there is a good reason everyone is moving toward the horst link design now that its not patent infringement

In the end - it likely comes down to what you like I guess! Cool projects man, keep it up!



Walt said:


> Just use a rocker to drive the shock or some other little linkage. Assuming you actually are having a problem with the shock seals or something. If you aren't, don't worry about it.
> 
> -Walt


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## shirk (Mar 24, 2004)

First a big "Hell Yeah" to all the steel FS stuff happening lately with the home builders and a few smaller custom builders. 

Second single pivot ftw. Read the reviews of the Evil bikes, ain't nobody have bad things to say and it's a single pivot with some funkiness to package the shock. But at heart it's single pivot. 

If cramming a water bottle into the main triangle isn't a must then a classic single pivot will allow you to get really really close to the shock rate of any bike on the market.

For pivot, use the 44mm headtube with 1 1/8th axle. It's stiff, I can't tell from the pics of your first build if that is what you used. I think you need a bit more beef in the tubing used in your first rear triangle.


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## Walt (Jan 23, 2004)

shirk said:


> First a big "Hell Yeah" to all the steel FS stuff happening lately with the home builders and a few smaller custom builders.


I'll second this. Awesome work as usual from everyone! Maybe I'll get inspired to burn some midnight oil the next couple nights and get my FS fatbike done.

-Walt


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## MDEnvEngr (Mar 11, 2004)

Shirk, the first 2 FS bikes I made I used the 44 mm HT as the pivot. The third one - "Colin's dually" I used a more standard bearings and axle setup. I used 2 bearings on either side - and could increase that to 3 bearings if I wanted. The problem I found with the headset is width - even with the "zero stack" headsets I had to do some funky stuff to have chainring clearance. Also, it places the bearings inboard. Putting the bearings in the swingarm keeps them further outboard. Beefier tubing perhaps...

I thought that Evil design was cool - a buddy had one and I looked it over on the trail. As I was looking at it my 11 year old says, "hey, that's a single pivot!". But i find it interesting that Weagle has been all about making the suspension design handle the squat forces...then his latest is a tarted-up single pivot.

I have to agree about the small builder FS bikes - lots of good inspiration here lately!

Can tell it is slow at work! B


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## Walt (Jan 23, 2004)

Everyone has pulled the plug for the holidays and apparently we are all too lame to think of anything else to to!

Funny thing is, I *like* some squat in my own bikes. Never enjoyed bikes with a lot of antisquat, they just feel boring and dead to me. 

-Walt


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## shirk (Mar 24, 2004)

Should be plenty of room with the 44mm pivot and single ring.

The clamp to the axle could be a bit narrower. I ran my headsets without their top caps to save some space. The clamps push directly on the split rings. Bearings are exposed and will shorted their lifespan but I've got a full season plus some of last fall out of a set.

My next version will move that pivot further back towards the rear wheel. Directly vertical above the bb.


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## todwil (Feb 1, 2007)

Heres my 3.25 cents (adjusted for inflation) single pivot placed about 1 1/2" forward of the bottom bracket, centering the pivot to the chainring you think you'll use. Find a
Foes/curnutt air shock these have large volumes of air and needed less PSI overall to operate and one of there z-link setups for lateral stiffness.


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## Feldybikes (Feb 17, 2004)

Having built several different single pivots ("true" single pivot and rocker-driven), I'll add that there's a lot of slop in designing a single pivot and still having it ride just fine. I don't think that's the case with a multi-link. Maybe FSR/horst-link has more room for error. However, I think that while there's more than one way to skin a cat, as it were, if you get the pivot locations a bit off with a short multi-link, it could screw up the way the bike rides pretty easily. 

And, FWIW, I think the VPP patent has expired while the DW patent is still in effect. If you care about such things, that is.

And +1 for homemade FS! Now I feel like a chump for recently having doubled my annual frame output for the past few years (1 to 2!!) yet having my FS project on the backburner.


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## Drew Diller (Jan 4, 2010)

MannaDesigns said:


> This would also give you a little more freedom with tuning the shock rate - thats why a lot of the smaller companies were using a "linkage driven single pivot" design before the FSR patent expired...


Same thing I noticed when drawing up one from scratch. It affords playing around, it (should) help with lateral play, it can be very compact to leave more of the front triangle for other stuff.

I had wondered before hand why such a large collection of companies did things that way, and just drawing it a few times gave that ...ohhh... I ge-e-e-e-t it....


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## CountryBlumpkin (Oct 14, 2010)

Let me know if you would like some input/sanity check on the linkage design. I've developed some code that will plot multi-pivot rear suspension through its travel. With this info I can calculate mechanical advantage ("Leverage ratio") over the travel. I can also get force vs. displacement, spring rate vs. displacement, anti-squat and pedal kickback.

The code is set up to do DW link suspension but I could pretty easily modify it to do VPP.

I don't claim to know what the "best" design is for each of those parameters, but the plots will at least let you know if your design makes sense. When you get into the floating swingarm designs, small tweaks to the link lengths can make significant changes to the rear axle path.















I've been nerding out on suspension design lately, it would be cool to put some plots up on this forum and get guys to comment.

EDIT: I just saw that the "Linkage" software will do everything I just proposed for a mere $25. Let me know if there is anything that won't do for you and I'll see if there is a solution that can come out of the kinematics code.


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## crank1979 (Feb 3, 2006)

Walt said:


> Bushings will suck bad after a few months. I would not do that if I were you.
> 
> Ride some different suspension designs and see what you like. It's really more a matter of feel (and marketing) than of actual objective performance.
> 
> -Walt


Don't tell Liteville or Nicolai that. I've got bikes from both brands and they successfully use bushings with less maintenance than I've done on my old Nomad or Firebird. I think if they are used properly they are fine.


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## Walt (Jan 23, 2004)

crank1979 said:


> Don't tell Liteville or Nicolai that. I've got bikes from both brands and they successfully use bushings with less maintenance than I've done on my old Nomad or Firebird. I think if they are used properly they are fine.


Come back in 5 years and let us know how they are working.

-Walt


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## crank1979 (Feb 3, 2006)

Walt said:


> Come back in 5 years and let us know how they are working.
> 
> -Walt


I was skeptical at first of bushings, having always had bearings. 3 years on with lots of wet sand riding (including on beaches) and they have held up better than any FS bike I've had with bearings. The Liteville is on it's second rear shock, 4th set of fork seals and second fork, crunchy wheel bearings repacked, etc and all I've had to do to the pivots/bushings is retighten them to the correct torque settings. Only 2 years on the Nicolai but it's just as reliable.

Bushings done properly can work and have been significantly less maintenance for me.


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## Smudgemo (Nov 30, 2005)

I haven't had any time to get going on my Titus rear triangle project, but I have been eyeing up bushings, too. I considered bronze, but what about Delrin? Cheap, easy to machine to size, good natural lubricity. Any reason not to bother?


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

Bushings could be great if tons of money was invested in their application, but that's not typically the case. Take the shock off a Knolly, move the stays through their travel, and tell us that's not wrecking the small-bump compliance. Older Turners were like that when new, too. I'd like to see needle bearings rather than ball bearings, but as a victim of the bronze-bushing era, I'm OK with bearings.

I used Stumpy stays for my FS bike, along with my own rockers and other changes. Building the front end to match up to the offset main pivot was a lot of fun.

The main problem with building your own multi-link bike is mass. It takes more material to accommodate all the pivots, and since we tend to work in steel, that means lots of weight. It's possible to build a steel front triangle that's not a total boat anchor, but the rear ends are a much bigger problem.

If you're OK with the axle path, chain growth, and anti-squat of single pivots, you can look at scissor links to reduce flex, and as others mentioned, to drive the shock with a specific spring curve. Foes was a heavy user of single pivots with scissor links.


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

Separate post about bushings:

Remember that bushings are the consumable in a pivot. They have to wear out without wearing the parts (excessively) around them. That means if you use bronze bushings you'll need something harder for them to run on, like steel. Heavy.

And the bushings need two precision interfaces, the press fit between the bushing and frame, because they must not move, and the tolerance between the busing and pivot pin. You'll have to hold a very tight tolerance between them to avoid friction or slop. The surface that the bushing runs on also need to be very smooth, preferrably precision ground.

I have a set of old Ventana pivots and bushings, which are a plastic-type material. They're completely loose until pressed into the correct ID hole. If anybody wants a deal on all that junk, let me know. Ventana now uses bearings.

I think that almost everybody is better off sticking with the ease and function of bearings.


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## jp08865 (Aug 12, 2014)

Smudgemo said:


> I haven't had any time to get going on my Titus rear triangle project, but I have been eyeing up bushings, too. I considered bronze, but what about Delrin? Cheap, easy to machine to size, good natural lubricity. Any reason not to bother?


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Not stepping on Walt or anyone else, just my personal experience. I'm no builder or engineer, just a dumb old maintenance mechanic. Years ago at work on one piece of machinery we were going through linear bearings and their hardened shafts like crazy. One night with no spare bearings in stock, I machined some Delrin AF bushings to get us through until bearings were delivered. Never did put bearings back in. Checked the bushing and shaft when machine was down, everything looked great. We used Delrin AF bushings from then on with very little (if any) problems.
In 2004, I needed to replace a couple of suspension bearings in my 2001 Giant NRS II so guess what. Not liking the use of ball bearings (point pressure on 2-3 balls at most) for an application that only rotates 20-25* felt I would try making up some bushings. Took a piece of Delrin AF round stock to the lathe and turned down a bunch of them, pressed them in and rode them right up to 2013, when I bought a new bike. Never dis-assembled to check them as their is no play in them to this day.


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## Eric Malcolm (Dec 18, 2011)

I would like to see someone make a bearing that will double for the use of BB axle and pivot. Seems to me that centring off the BB shell is the best place to pivot from. May be this will be next years 'Big Thing'.

Eric


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## MDEnvEngr (Mar 11, 2004)

Thanks for the thoughts fellas. The only advantages to bushings to me would be the cost and weight - those igus bushings are cheap. There is little downside to bearings - especially when sticking to a single pivot design. A multi link design that has 4 sets of pivots might be different. Regarding the weight of the multi link design fabricated in the basement - this is a great point. 

I am not dissatisfied with the performance of the single pivots I have made so far. I can deal with the squat and bobbing - I do wish they weren't so squishy when I stand. But I'm getting used to sitting more and as I've said strava doesn't lie. So, for the next one I think I'll stick with single pivot on bearings - but will use some sort of scissor link up top to provide a bit more stability. Even this is a "perceived" problem: any wiggle on the top when yanking side to side on the rear tire seems bad - but I can't feel anything. 

It will be a 29er for the squeeze this time. 

Happy holidaze everyone. I hope you all aired your grievances yesterday. B


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## Feldybikes (Feb 17, 2004)

MDEnvEngr said:


> Happy holidaze everyone. I hope you all aired your grievances yesterday. B


Given the general makeup of this forum, I suggest we substitute a 4130 pole.

(for those in the dark: link)


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## dr.welby (Jan 6, 2004)

Eric Malcolm said:


> I would like to see someone make a bearing that will double for the use of BB axle and pivot. Seems to me that centring off the BB shell is the best place to pivot from. May be this will be next years 'Big Thing'.


It's been done, for example the Lenz Concentrilink.

Pivoting around the BB is very squatty, so it's been abandoned by everyone who tries it.


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## Jayem (Jul 16, 2005)

Walt said:


> There is a reason the industry has gone away from bushings. They develop lateral play and slop, they stick, etc. Just in general not as functional and reliable as bearings.


Err, maybe you are referring to the throw-away teflon/bronze impregnated bushings that came on the first FS bikes, those are nothing like the IGUS bushings with grease ports that turner used. You're flat out wrong here.

5 years later, my turner was great, but bearings won't last that long because the suspension is usually resting on 2-3 ball bearings, which pit and grove over time, which causes play, which causes metal parts slamming against each other on any impact, which ovalizes the bearing mount if left unchecked. I've never had a bearing-bike last anywhere near that long. IGUS bushings with greaseports on the other hand, perfect for a limited-rotation role like bike suspension. As said earlier, it usually requires pretty good tolerances, which turner was able to do, since they were making their bikes in-house. The whole perception that bike suspension pivots should be ball bearings is somewhat perplexing, as the type of bearings that have traditionally been used are low-load high rotation, terrible for the application they are used in. The headset and crankset are much better examples of proper applications of bearings.

Tapered bearings have the potential to "do it all", but they are extremely difficult to engineer into tight/small spaces. Benefits include being able to deal with multiple force directions and much more surface area than ball bearings. This increases complexity significantly.

A good bushing system is usually the next best, as the lateral rigidity is great, for the limited rotation they hold up well, especially when paired with groves in the axle and grease ports. Then you can purge the old grease, introduce new grease, at the least keep positive pressure on the system to help keep contaminants out.

If not the above, then there's angular contact bearings, which are ball bearings with offset "races", much better for dealing with side loads than regular ball bearings.

Then there are run of the mill ball bearings, which can be doubled up sometimes (like Ventana does) to increase rigidity, but unless one is careful about selection of the proper type of bearing, you start to run into a lot of negatives fast IMO. This is one of the prime reasons why a lot of bikes just disintegrate in a season or two IMO. Not much thought is given to the bearings and they are not designed with grease ports or the ability to easily change them (without taking the entire bike apart and using a blind puller). For some reason though, people are absolutely fascinated with the ball bearings. They believe some slight "stiction" in the system is going to impact the ride big time, when there's a 400lb spring on the bike and stiction compared to what it takes to start moving the spring is simply infinitesimally small. Mind you, I never experienced this when I had my shock off, my bushing suspension moved great, but I shot some grease in every few months. Still, people seem to be fascinated with ball bearings for some reason.

Needle bearings have some advantages, but they don't deal with sideloads at all and have to be paired with bushings on the sides to make up for this, they are also difficult to design into little spaces, making them more effective for main pivots.

I'd say the reason the industry went away from bushings, like Turner and some of the quality manufacturers used, is cost. It's far easier to spec some cheap skateboarding or rollerskate type bearings and slap them in there and not worry about what happens a year later when the warranty expires. It may not be quite this simplified, but don't think the long-term durability is high on the list for the next model year of Specialized, Trek, etc.


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## Syltmunk (Jan 20, 2008)

Jayem said:


> Err, maybe you are referring to the throw-away teflon/bronze impregnated bushings that came on the first FS bikes, those are nothing like the IGUS bushings with grease ports that turner used. You're flat out wrong here.
> 
> 5 years later, my turner was great, but bearings won't last that long because the suspension is usually resting on 2-3 ball bearings, which pit and grove over time, which causes play, which causes metal parts slamming against each other on any impact, which ovalizes the bearing mount if left unchecked. I've never had a bearing-bike last anywhere near that long. IGUS bushings with greaseports on the other hand, perfect for a limited-rotation role like bike suspension. As said earlier, it usually requires pretty good tolerances, which turner was able to do, since they were making their bikes in-house. The whole perception that bike suspension pivots should be ball bearings is somewhat perplexing, as the type of bearings that have traditionally been used are low-load high rotation, terrible for the application they are used in. The headset and crankset are much better examples of proper applications of bearings.
> 
> ...


Great post Jayem, totally agree, built me a fs frame about 3 years ago with bushings Turner style but made of delrin I ride 40-60 miles a week and still nice and tight, and I have ridden Turners for several years with no problems, one of my riding buddies has a Giant with ball bearings and he goes thru a set of bearings a year at least, imo bushings a far better choice if done right.


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## customfab (Jun 8, 2008)

Walt said:


> There is a reason the industry has gone away from bushings. They develop lateral play and slop, they stick, etc. Just in general not as functional and reliable as bearings. They are super cheap and light, though, which is why they still occasionally get used for stuff. I think your 15 year old bike is probably the exception (hell, any fully functional FS mountain bike that age is the exception!)
> 
> -Walt


There's a few thousand different materials you can make suspension bushings out of and it's not reasonable to lump them all into the same category. Suspension design also has a large part to play in what will work well.


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## shirk (Mar 24, 2004)

Biggest reason why I used the 44mm headtube as pivot is tooling and tubes. 

No extra tooling or special machining needed. I use the same reamer/facer as required for the ht. 

For a guy in a garage trying to keep this as cheap as possible and limited tooling it makes a huge difference. 

Perhaps a 1 1/8th headtube stock for shell and igus bushings with a 1 1/8 th steer tube could work in a similar fashion. Someone would need to see if Igus makes a suitable bushing to meet those specs. Would the od on the steer be a tight enough tolerance to play nice with bushings?


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