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I have a 1960 T100A 500. It has a custom front end that I think is 1970 650cc from the steel sliders (pre-1971) with 70+ style axle caps/studs, P-clamp handlebar style upper triple clamp with no numbers. The bottom bearing is stupidly loose, like the race isn't the right size or the balls aren't contacting. Going back to the "proper" parts is just not possible where I'm at in the US, especially since the fork tubes are custom longer units from Frank's and the neck may be raked to match, etc.

I want to find bearings that fit instead or some conversion. I could convert to tapered bearings if I knew the right ones because the top bearing's upper race is shot anyway. I see tapered bearing kits that fit 56-70 650's and 67+ 500s, but what would I need to do to get the bottom to mate up properly? I can't find ID/OD measurements anywhere.

I have some photos but I don't know that they'd be particularly helpful. I can take measurements if it helps. This is holding up the entire bike, which is now in pieces on a jack in a car port with fall and winter weather heading in!

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Might try a call to All Balls or Lowbrow Customs.


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Has to be others here that have done this, but pulling the forks and measuring everything is probably the only way. Determine what size tapered bearings would fit and call Dixie Bearing Co etc... and tell them what you need. Should be easy to get bearings to fit but then you may have to shim vertical distances with washers or? I'd certainly try to use tapered bearings, hope somebody chimes in with real help soon.


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Originally Posted by The Momes of Wrath
I have a 1960 T100A 500. The bottom bearing is stupidly loose, like the race isn't the right size or the balls aren't contacting.
The early C series employed smaller OD bearings than the B series. I believe the ID was the same. You simply need the correct bearings. Ask CBS.
Why your bearing is so loose will probably become apparent when you dismantle it, but I bet they've used 5TA outer race and balls and a later "big bearing" inner race.

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Fitting taper bearings is not always a step forward. A lot of leading manufacturers and some race teams are using the ball bearing and cup.

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Yeah, I'm finding that the exact inner and outer dimensions are hard to match at the same time because it's 1/2 mm increment or an odd size like 1-29/32. Otherwise I can wait on something custom made in China, then it's still too tall of a bearing compared to the ball bearings. I'm also having the same ID/OD problems with the ball bearings. I know someone must have done it correctly but idk who or where or when.

I can get too small of an OD and try to shim it (not a good time IMO), too big of ID by 1MM and the same problem but worse, or too small of an ID by 1 mm and shave it a bit and hope the inner race doesn't jam too badly on the stem. I have a set of inner bore gauges, micrometer etc and if I ever need to remove it and it's stuck too tight, I'll use the tried and true method of grinding it thin and giving it a good whack with a "fine adjustment tool". Splits the hardened race every time, especially with a slight interference fit.

The only problem is my entire front end needs to be assembled, disassembled, this done, then reassembled... or wait for a month with it in pieces. If only they'd used an industry standard machine bearing size to begin with, and then the parts would be 1/4 the cost. Oh well.

Last edited by The Momes of Wrath; 09/16/22 5:51 pm.
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Winter is coming soon to the Midwest.
"Riding season" will be over in two months.

Take your time to get it right.
Knowing how long winters are here, you'll have 4 to 6 months to figure it all out.

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Last edited by AngloBike; 09/17/22 9:24 pm.
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