Low friction material for a bushing

SamI

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Hi guys,

I’m a keen mountain biker and I’m getting fed up of the bushings in my rear shock wearing rapidly. Well, I don’t mind them wearing but they are quite expensive! This got me thinking, why not just make some myself and keep a bunch in the drawer so I can swap them out as needed?

So my question is, what to make them from?

The existing ones on my bike are a plastic bushing that is pressed into the shock with an aluminium shaft running through it. I have seen some people run a brass shaft (I’d probably prefer bronze myself) through a plastic bush but is there any merit in running two bearing materials against each other?

The ultimate aim would be to reduce friction as the difference can be noticeable when out on the bike (I used to run needle bearings but these seemed to come out of the box with a little play which worsened rapidly. they did make the suspension much more supple though).

I was thinking a plastic DU bush and a bronze shaft but if there won’t be any improvement over a steel shaft then I won’t bother with the added expense. I was thinking D2 tool steel hardened to somewhere around the 52 HRC mark if not bronze.

Any help would be greatly appreciated!
 
check out Vesconite I am running them as link pin spacers for my offroad buggy kinda expensive stuff. the other I have used is a nylon with moly impregnated into the material. I am no expert but this has worked for me.
 
Nylon would work for that. It won’t squeak and will last a long time. I have made them for 3 wheel ATVs and they hold up for same purpose.

Just do the bushing by itself not the shaft.
 
An off road bike gets dirty. Is the shock assembly designed to keep all the dust, dirt, and grit out of it? What it is made out of doesn't matter if it is always contaminated. Make sure that issue is addressed first. Sometimes the designers use the frame itself as the "clean space", and only have seals where the parts slide into the frame. The inside of a bike frame is not a clean place. Another issue is having oily rods out where the grit is. That is a lapping machine. After all that is considered, then think about maybe changing materials...
 
If you look at the stock bushings from Fox and Rock Shox, they are a slight press fit and come from the factory with a loctite compound on the mating surfaces. If the bushing fails, you're a mile away from destroying the mounting eyes on your shock.

When I ruin the stock bushings after a season, I go straight to RWC at enduroforkseals.com and get their needle bearing retrofit kits. I've put them on a number of bikes, raced them hard, and never had a problem.
 
Teflon will spread under pressure. I use it for telescope bearings where the very low stiction is a bonus.
I would go sealed needle rollers.
 
When I replaced the rear shock bushings in my MTB I turned some bearing bronze shock bushings and used a titanium through bolt. Seemed to work well, the previous shock had aluminum bushings with a SS bolt. The shock travel is short and the pivot movement is small, all the other suspension pivots use sealed ball bearings. A big problem with these bearings is no matter how good the seals are water and moisture get in and they get pretty nasty. The needle bearings from RWC have seals, but if you get the bike wet a lot I might opt for something simpler and use some Teflon grease to keep the moisture out. If you have a long travel rear suspension, the needle bearings would give the least friction, bearing bronze bushing may be more durable. UHMW (ultra-high-molecular-weight polyethylene) might be an option. Turning UHMW is difficult from what others have posted.
 
Thank you all for the replies - it's good to know I'not the only mountain biker!

Something like this maybe: https://www.mcmaster.com/bronze-sleeve-bearings
Hardened shaft for that to run on would be nice.
Being familiar with (dirt) motorcycle shocks, the shafts are hard chrome, but they are running needle bearing on them also.

I did consider oil impregnated bronze. I did a very quick search and couldn't find anything of a suitable size for my shock and it seems that it isn't available in bar form. That being said, it was a very [very] quick look.

An off road bike gets dirty. Is the shock assembly designed to keep all the dust, dirt, and grit out of it? What it is made out of doesn't matter if it is always contaminated. Make sure that issue is addressed first. Sometimes the designers use the frame itself as the "clean space", and only have seals where the parts slide into the frame. The inside of a bike frame is not a clean place. Another issue is having oily rods out where the grit is. That is a lapping machine. After all that is considered, then think about maybe changing materials...

That's a fair point. The modern Fox bushings come sealed with o-rings and seem to do a fairly good job of keeping the grime out. The shock and the frame is exposed to the elements however the frame itself acts as a shield so mud and water isn't directed at the bushings. The bushings are installed dry so as not to attract dirt.

If you look at the stock bushings from Fox and Rock Shox, they are a slight press fit and come from the factory with a loctite compound on the mating surfaces. If the bushing fails, you're a mile away from destroying the mounting eyes on your shock.

When I ruin the stock bushings after a season, I go straight to RWC at enduroforkseals.com and get their needle bearing retrofit kits. I've put them on a number of bikes, raced them hard, and never had a problem.

The newer DU bushes that come stock on Fox shocks are a plastic of sort and do not come with any form of retaining compound on them (see below). I can't vouch for Rockshox as I've not run any of their rear shocks before.

1546502360117.png
I have tried the needle bearings from enduro. The first one I tried was sweet and lasted about a year and a half. It made a huge difference to the feel of the bike. The next three however the shaft was a sloppy fit in the bearing so there was play in the bearing before I'd even hit the trail. Eventually the play drove me mad and I reverted back to standard bushes.

Teflon will spread under pressure. I use it for telescope bearings where the very low stiction is a bonus.
I would go sealed needle rollers.

That's good to know about teflon and it is certainly something I shall consider before using any!

When I replaced the rear shock bushings in my MTB I turned some bearing bronze shock bushings and used a titanium through bolt. Seemed to work well, the previous shock had aluminum bushings with a SS bolt. The shock travel is short and the pivot movement is small, all the other suspension pivots use sealed ball bearings. A big problem with these bearings is no matter how good the seals are water and moisture get in and they get pretty nasty. The needle bearings from RWC have seals, but if you get the bike wet a lot I might opt for something simpler and use some Teflon grease to keep the moisture out. If you have a long travel rear suspension, the needle bearings would give the least friction, bearing bronze bushing may be more durable. UHMW (ultra-high-molecular-weight polyethylene) might be an option. Turning UHMW is difficult from what others have posted.

The frame is a Santa Cruz Tallboy LT. The issue with the VPP suspension design seems to be a high range of motion in the lower link which causes rapid wear and i have seen a number of people complaining of this online. I agree that in theory a needle bearing makes more sense but from past experience they are not reliable enough. Thanks for the suggestion of UHMW though - certainly something to look into!
 
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