Triumph pre-unit upper neck bearing issue

1588 Views 4 Replies 4 Participants Last post by The Dewd, Nov 18, 2011

The Dewd

Discussion Starter · Nov 17, 2011

I just took a look at the top portion of the Tiumph pre-unit single down tube frame loop I have in order to tap in the tappered roller bearing conversion cups. The bottom of the neck has a recess that alows the cup to be tapped into while the top of the neck doesn't.

It looks like only the stock smaller bearing will fit in it. Is there a solution for this? I am using Ceriani trees (thus larger diameter stem) so maybe this is part of the issue? Do I machine and weld on a recess to the frame that will accept the roller bearing conversion cup then just like the bottom of the stock neck has? Any help is appreciated. Thank you

Save

1 - 5 of 5 Posts

BobAsh

· #2 · Nov 17, 2011

I'm sure some one here will chime in with more detail, but there is a range of years of preunit that have the small upper bearing and the roller conversion won't work.

I have the roller bottom bearing and stock loose balls in the top of my 54.

Save

38speedtwin

· #3 · Nov 17, 2011

If it is a pre-1956 frame, then the bearing conversion kit will not work. I have seen a few kits that were made to work on the early frames, but not in a long time. If you have an early frame, you can always modify the headstock, or machine a custom top race to take the roller. I have seen both done well.

-Shaggy

Save

lowbrowcustoms

· #4 · Nov 17, 2011

I just run the roller bearing in the bottom and the stock loose ball bearings in the top.

Tyler

Save

The Dewd

Discussion Starter · #5 · Nov 18, 2011

Thanks for the replies - I will have to look at teh loose ball setup - I dont have the stock pre-unit stem but I think the ceriani stem has a larger outer diameter than the tirumoph one. In addition, I dont know the original pre-unit top tree or bearing setup even looks. I dont think the two peices are simialr enough to where i can just use the original loose ball setup.

Save

1 - 5 of 5 Posts

This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.

Top Contributors this Month