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Author Topic: USD Fork swap.....what should i make this bushing out of????  (Read 5855 times)

Offline MILLENNIUM FALCON

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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

Offline fade2nada

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Re: USD Fork swap.....what should i make this bushing out of????
« Reply #1 on: May 21, 2013, 12:46:26 »
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!
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K5 GSX-R 750 1992 Suzuki GSF-400 Bandit 72 & 75 T500 2STROKE 1979 KZ650D Project Bike

Offline Bozz

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Re: USD Fork swap.....what should i make this bushing out of????
« Reply #2 on: May 21, 2013, 12:51:14 »
Machining a bushing seems like more work than machining a new stem for the trees, no?
Cheers!
-Bozz

(All opinions worth less than you paid for them!)

05 FZ6 - 99 ZRX1100 - 93 GSXR750 - 82 GL500 - 78 GL1000 - 77 KZ900 - 77 CX500 - 60 R60

Offline MILLENNIUM FALCON

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Re: USD Fork swap.....what should i make this bushing out of????
« Reply #3 on: May 21, 2013, 13:34:49 »
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.

Here are the sizes i need.

28x47x15

28x55x17

Offline Tim

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Re: USD Fork swap.....what should i make this bushing out of????
« Reply #4 on: May 21, 2013, 13:57:43 »
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.

Might be an option vs. a really thin 1mm bushing.
"Quality . . . you know what it is, yet you don't know what it is. But that's self-contradictory. But some things are better than others, that is, they have more quality. But when you try to say what the quality is, apart from the things that have it, it all goes poof! There's nothing to talk about. But if you can't say what Quality is, how do you know what it is, or how do you know that it even exists? If no one knows what it is, then for all practical purposes it doesn't exist at all. But for all practical purposes it really does exist."

Offline hillsy

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Re: USD Fork swap.....what should i make this bushing out of????
« Reply #5 on: May 21, 2013, 23:55:44 »
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.
 
What is the front end off that has the 28mm stem?

Offline MILLENNIUM FALCON

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Re: USD Fork swap.....what should i make this bushing out of????
« Reply #6 on: May 22, 2013, 02:17:21 »
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. 

Offline hillsy

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Re: USD Fork swap.....what should i make this bushing out of????
« Reply #7 on: May 22, 2013, 04:00:04 »
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.

Offline VonYinzer

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Re: USD Fork swap.....what should i make this bushing out of????
« Reply #8 on: May 22, 2013, 10:24:35 »
What Tim said...

Have a shop add material by welding and machine to spec. That bushing will fail.
Like a river that don't know where it's flowin'
I took a wrong turn and just kept goin'

Offline Tim

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Re: USD Fork swap.....what should i make this bushing out of????
« Reply #9 on: May 22, 2013, 17:27:16 »
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.
"Quality . . . you know what it is, yet you don't know what it is. But that's self-contradictory. But some things are better than others, that is, they have more quality. But when you try to say what the quality is, apart from the things that have it, it all goes poof! There's nothing to talk about. But if you can't say what Quality is, how do you know what it is, or how do you know that it even exists? If no one knows what it is, then for all practical purposes it doesn't exist at all. But for all practical purposes it really does exist."