I recently got an old Novara Randonee touring bike, it has 27"x1 1/4 Araya 36H alloy rims laced to Suzue hubs and Shimano cantilever brakes. I put in the requisite few hours cleaning, repacking, and truing different bits of the bike because I had noticed a slight wobble in the front wheel that was causing the brakes to catch at one point on every rotation. After an hour of truing I've eliminated every wobble in the rim (I think) but the braking problem persists.
I noticed that it always catches at the point directly across from the valve stem which (I assume) is the seam of the rim. I don't have a set of calipers on hand, but is it conceivable that the rim is wider at the seam than elsewhere? At every rotation, this spot on the rim causes the front end to shudder with the force of braking, and (call me paranoid) I can't help but think that has to be pretty bad for a headset. Is there any risk of damaging the head tube, etc. during hard braking? This is a touring bike, so it's likely to be subjected to heavy braking loads over time.
Is there anything to be done about this? Could it be filed down with fine-grit sandpaper if it is indeed wider, or will this damage the rim?
Thanks for the help, everyone.