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I am swapping to USD forks and the closest bearing I can find has a 2mm larger inside diameter than the triple tree stem. So i will need to make a bushing to press onto the stem to fit the new bearing. The bushings will be about 17mm in length, (i.d)28mm (o.d) 30mm. I'm just looking for some insight on materials for this bushing. Thank you
Don't shim anything. Get the right tapered bearings at allballsracing.com
They have a fork conversion page already setup. Easiest part of USD fork conversion process!
Ive spent hours searching and calling. Ive tried all the companies around. the bearing i need doesn't exist. haha. I tried all balls. I ended up ordering my bearings from them but they are perfect.....but as close as I can get. If you can find it ill order it haha. making this bushing will be very simple. Much less work than a new stem. I was just getting some opinions on what material to make it out of.
I had a similar problem when I modified my late XS650 tree to fit in an earlier XS frame (shorter steering tube on earlier frames).
I had a machine shop remove the stem, and then cut an inch off the bottom and weld it back into place. Unfortunately we didn't anticipate the bearing seating area being removed in the process, and that left the stem a little small for the bearing in it's new location.
So, the stem came back out, and they added some material to the stem with weld. Then it was turned on a lathe to the right diameter for the bearing.
A bushing that thin will more than likely be crushed when you try and press the bearing onto the stem (the bottom bearing at least). You probably need to do a stem swap.
i just machined the bushing to see what it would look like.....i am confident (fairly haha) that I can press it on there without crushing it. i'm not going to make it quite as tight as the stock bearing. The stem is off of a rm125
!!WARNING STUPID QUESTION!!
why does the lower bearing need to be pressed on TIGHTER than balls but the top bearing just slides right on? It seems to me that if everything is properly fitted and assembled nothing would move even with a slip fit on both bearings. The stem has a cir-clip on the bottom to keep it from pulling through and there is a nut on top to keep it from moving the other way.
The bottom bearing holds the weight of the motorcycle - the top bearing pretty much just "centres" the stem / top clamp. Any play in the bottom bearing will result in rapid wear / failure.
The top bearing needs to slide in order to be able to adjust the pre-load on the stack to eliminate slop in the stem, and to make it possible to assemble/disassemble without tools. If the upper bearing was pressed into place, it would basically be impossible to take the front end off.
The press fit lower bearing is presumably better than having it a slip on fit as it takes the brunt of all the vibration/impact etc. and any slop between the stem and bearing would ultimately lead to a nasty catastrophic failure of some form.
It wouldn't be a "catastrophic" failure - the bearing would slop around on the stem and eventually the bearing would wear out....but the triple clamps would still hold everything together (IE: the front end won't fall off).
Handling would become pretty vague though - and every time you braked you would probably hear a nasty CLUNK as the bearing moved about. You'd probably stop riding the bike a long time before the bearing actually collapsed because the noises and movement would freak you out.
It wouldn't be a "catastrophic" failure - the bearing would slop around on the stem and eventually the bearing would wear out....but the triple clamps would still hold everything together (IE: the front end won't fall off).
Handling would become pretty vague though - and every time you braked you would probably hear a nasty CLUNK as the bearing moved about. You'd probably stop riding the bike a long time before the bearing actually collapsed because the noises and movement would freak you out.
Well, if the lower bearing got bodged up and locked up somehow, I'd class that as catastrophic No question that would be unlikely and you'd more than likely get plenty of warning - just postulating on why the lower bearing is pressed on vs. slipped on like the upper one.
Even a worn lower bearing can cause a tank slapping wobble and high side. I consider falling off the bike or hitting something while moving a catastrophe.
Ymmv
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I think we can all agree that "catastrophic failure" is generally a bad thing. HAHA
I wise man once said......."No movement = No wear."
I have everything assembled I will upload some pictures later. I made the bushings with shoulders on them so they have absolutely no where to go. I had to freeze the stem and heat the bushing prior to pressing them on to get them to fit without damage. Everything tightened up nicely. My plan is to ride it for awhile checking it for play after a few rides. In the meantime I may look for a new rm stem. I found out 1 model year newer bikes use a 30mm stem so I wouldn't need a bushing. Like previously stated I think if anything does happen it will be a condition that slowly gets worse over time. I doubt the front half of my bike will explode while cruising down a fire road.....but you never know haha.
Took it for a ride today.....handled great and felt much better than stock... Ill update you on the bushing wear.
So Far I have a total of $53 in the fork swap.
I think we can all agree that "catastrophic failure" is generally a bad thing. HAHA
I wise man once said......."No movement = No wear."
I have everything assembled I will upload some pictures later. I made the bushings with shoulders on them so they have absolutely no where to go. I had to freeze the stem and heat the bushing prior to pressing them on to get them to fit without damage. Everything tightened up nicely. My plan is to ride it for awhile checking it for play after a few rides. In the meantime I may look for a new rm stem. I found out 1 model year newer bikes use a 30mm stem so I wouldn't need a bushing. Like previously stated I think if anything does happen it will be a condition that slowly gets worse over time. I doubt the front half of my bike will explode while cruising down a fire road.....but you never know haha.
Ive spent hours searching and calling. Ive tried all the companies around. the bearing i need doesn't exist. haha. I tried all balls. I ended up ordering my bearings from them but they are perfect.....but as close as I can get. If you can find it ill order it haha. making this bushing will be very simple. Much less work than a new stem. I was just getting some opinions on what material to make it out of.
Did you really mean this "I ended up ordering my bearings from them but they are perfect.....but as close as I can get."?
What did you give for the front forks?
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