dbg

Restoring an old tandem (mel pinto special) and discovered the fork threads (1-1/8 threaded) were pretty badly jammed up where the top bearing race sits. Some of the bearings were crunched also. The races themselves seem OK. I'm guessing some broken bearing got wedged down against the threaded section and wore it down pretty good.

I'm getting to the question...

I've chased the threads back down over some of the worn area (very small improvement) but it may not be enough to fit back together and function smoothly. It will be hard to replace this fork. So now I'm thinking I can replace the 5/32 bearings with 3/16 and extend the race-bearing areas just enough to not ever encounter the bad area. They seem to fit OK.

Anybody see anything wrong with this?

HillRider

Interesting concept. I'm surprised a 1/32" height increase (or 1/16" if you do it to both races) is enough to make a difference. Assuming the headset continues to turn smoothly, one problem I see is the larger bearings will open a larger gap between the top cup race and the adjustable cup race and allow dirt and water easier entry.

One possible fix is to replace the headset with one having a greater stack height if there are any spacers used with the current headset.

dbg

I had planned to replace the headset but I consider that a crapshoot for a couple of reasons. I'd need a headtube bearing race that sits up higher after being pressed in, and/or thicker lower headtube race or taller crown race. Hard to know those details, and these look thicker/taller than normal already. It might be more likely to make it worse. Taller stack height won't really raise the spot where the headtube race meets the threaded-on race. It just adds height above that point.

AND then there is this: it is a 30+ yr old French tandem. It looks very much like a 1 1/8 threaded fork and headset but something seems a little off. It might not actually fit a new, standard 1 1/8 threaded headset.

If I replace the headset, I may need to be ready to replace the fork also, and that's a path I don't especially want to take.

HillRider

Older French bikes had their own threading standards so you may not be able just to fit a new headset. Let us know if the bearing swap works.

dbg

UPDATE:
I'm pretty sure it is an older French headset (thanks CaptBike) that was supposed to have 5/32 on top and 3/16 on the bottom. They were definitely both 5/32 and probably cheap quality since several on top had crumbled and wedged between threads and bearing race to cause this problem originally. (So now I'm suspicious of the original Mel Pinto build as I know the bike's total history and it has never had the headset serviced. I think they cut corners. Hmmmm.)

But I replaced both with 3/16 and it definitely lifted it enough to avoid the mangled threads. There is a minor gap increase on top where I can almost see into the bearings area. If I can't figure out a way to cover it, I may have to keep an eye on it. Don't want it collecting grit. But overall the headset now works perfectly.