Dent in rear rim. How serious is it?
 

I took my Specialized HR in to the shop to get a complete tuneup, and when it was done, the mechanic told me there was a small dent in the rear rim. It just bulges out very slightly and you can feel it if you rub your finger across it. He also said he wasn't able to completely true the rear wheel completely because of it. He said it didn't look serious and that the rim should last for a long time.

Well, I just read in Bicycling magazine yesterday in the current issue that a little "ding" like that could cause the rim to fail when the brake pad hits it. I thought maybe something could happen if I went over a large bump just as that part of the rim was in the down position, but never thought the brake pad would cause a problem by itself.

Does anyone have a second opinion?

i got a bike a while ago that had 3 major dents in the rear rim. i never had any problems, either with big bumps, or braking.

The rim could fail, or the tire could come off the rim at that spot. Either one is a recipe for disaster.

The mechanic gave you sound, conservative advice as he should, and while its possible the rim may fail, I have fixed dinged rims by bending them back in line, and then filing the braking surface so the ding doesn't catch on the brakes, with no catastrophic results.

If you think the rim is so bent it won't hold the tire, pump the tire up to 10-20 PSI above max momentarily and if it holds, you should be ok.

You or the mechanic needs to fix the dent.

The mechanic probably told you he could not "true" the wheel because that would've meant leaving a few spokes near the ding with too much or too little tension. If that is the case, then the wheel was probably left reasonably well tensioned but out of true and therefore unlikely to suffer a catastrophic failure. I've ridden with a few dings myself and all but one of them was small enough to allow the wheel to be trued back up. The last one could not be trued because relatively even spoke tensions could not be maintained. Granted I am kind of anal about my wheels but I found it to be very annoying. I could feel the wobble under hard cornering and I hate following other riders whose wheels aren't true let alone looking at my own. I eventually sourced an identical rim and did a lace-over to fix the problem. A lace-over is much cheaper that having the entire wheel relaced with an entirely different rim.

Thank you for all the quick replies! I guess mine "ding" is pretty minor then and I guess I won't worry about it too much. I avoid big bumps (except railroad crossings) and ride pretty much all onroad, so I won't have to worry about that too much I guess.

Remedies depend on the nature of the ding. Is the braking surface bulging out a bit near the edge?

If so, you can simply use a finger-tightened adjustable wrench to gently cold-set it straight. Just try not to over-compensate, because too much back and forth can start to fatigue it.

Once you get it pretty straight, get some 100 grit sandpaper and wrap it around a small piece of wood (sanding block). Gently sand the area until there are no high spots to catch the brake pad. Sand in an arc tangential to the circumference of the rim (not up and down radially) -- sand like you're a brake pad. Once you get the high spots out, stop sanding.

Should be just about as good as new.