I am reassembling the headstock on my bike but the top inner race of the new taper bearing is a slightly loose fit on the column. Seems to be about 4 thou play. Is that acceptable?
If not, how can I shim it and with what? Are bearing adhesives suitable?
The bearing race should be an interference fit in the column but I understand in this case it is a loose fit?
The fit of the top and bottom races should be similar and so, if the bottom race is still an interference fit, I would measure everything up to check the OD of both races is the same and to check what the difference in ID is between the upper and lower sections of steering head column. It's very hard to see why the ID of the upper section of column would have changed and be bigger than it should be?
At the end of the day, if the ID of the upper section of column turns out to be too big, the 4 thou gap can sorted using a high strength Loctite retaining compound - I would start by considering Loctite 640.
Thank you spaceman. The bottom bearing is an interference fit but had to be shimmed by a professional when I had the forks done. The top one is loose but seems better than the lower one. I think the shimming of the lower one was done with old feeler guage leaves. I could try the same I guess with the top one but it is much more challenging to do as everything has to be in place at the same time as the shim in and gravity is against you. I may try both Loctite 640 and shim. I gather i640 s quite low viscosity, so I will need to avoid it dripping through.
I wonder why the races are a loose fit in the steering column - I don't think I've come across that before?
I've used Loctite 640 before but I see that Loctite 638 will tolerate gaps of up to 10 thou and may be better in this case. I would aim to assemble the steering head in place after applying the Loctite 638 without any grease so that you can be sure the bearings are seated correctly and everything turns smoothly. You will probably need to leave it for 24 hours for the Loctite to fully cure.