My steel coker rim (actually a QuAx one I think) is narrower at the joint than the rest of the way round. It’s not bent, it’s just very poorly made (looks like it shrunk when it was welded together into a hoop). It doesn’t affect the tyre fitting but is enough to make the brake extremely juddery.
Up to now I’ve just put up with it - I only used the brake on one steep hill on the way to work anyway and with 150mm cranks I could control the lurch once every wheel revolution.
But recently I’ve been doing more road riding, practising for the Unicon marathon (otherwise I ride mostly on xc trails), and wanting to experiment with shorter cranks. It would be nice to be able to use the brake occasionally (especially when my legs are starting to get tired), but at speed it’s just too dangerous with the wonky rim.
It’s not bent so I can’t just tweak it out like I would with a pranged steel bike rim (the whole section of the rim is smaller at the joint). I thought about hammering it out from the inside against a flat surface, but I think it’ll be pretty hard to do that without ruining the tyre seating and risking the tyre falling off. Then I thought about filling the “dent” with some sort of metal filler and filing it smooth, a bit like lead loading in car bodywork but with a harder filler. There are various metallic fillers on the market, but I’m wondering if any will stick well enough, even if I file away some of the plating first.
Anybody ever tried anything like that or heard of anybody doing it? Or any other suggestions for straightening up the brake surface? I know I could buy a new rim but I’m trying to avoid throwing money at it if I can help it.
Otherwise, is it that the two parts don’t match up, so there’s a jump, or is it that it goes smoothly in and smoothly out, but that still screws up the braking? I know some people have had grinders at their rims to smooth jumpy bits off at the rim join, although obviously depends on how much of a jump it is.
Thanks for the replies. I don’t think I described it clearly enough - it’s not just a rough joint that can be ground down, like on the airfoil rims, and it’s not that the pads grip too much at one point like on a dirty rim. The whole rim is actually narrower at the joint, like an hour-glass shape over about two inches. I know it’s a cheap rim and I could buy a better one, but that’s not the point - it’s proved to be strong enough for my riding and I don’t have money to burn if it’s not necessary. It’s not that I can’t afford a new rim if I had to, but then it would be silly to keep the heavy 12-gauge spokes and the hub has been drilled for 12-gauge, so I’d probably end up buying a new wheel… and I’m not going to get much for my existing wheel am I?
I’ll try to sort it out some how - nothing to lose really. If it doesn’t work I’ll have to buy a new rim.
My first thought would be to braze over it. Trying to fill up the area with brazing rod might not look the neatest of jobs, but I’d expect it’ll bond well enough with the wheel (as long as you strip the chrome off), and if it’s filed smooth, should be grippy enough with the brakes.
My second thought, however, was that if it’s a very deep area to fill then you might end up with enough metal in there that it’ll unbalance the wheel enough to notice. So you may have to put some counterweights at other parts. But then you’ll end up with a VERY heavy wheel.
That’s not a bad idea - I thought about doing it with weld but thought there was too much chance of distorting the rim even more. Brazing might be a good compromise between weld and filler. I don’t think the weight will be a problem - the whole wheel weighs such an enormous amount anyway and it’s not exactly running at high rpm.