When To Replace A Rim?
 

I have a Mavic Open Pro 32 spoke wheel that I used for commuting and cyclocross this fall into the shop the other day, and when they called to tell me it was ready, they said something to the effect of "well, we got it as true as we could. You know it was in pretty bad shape. Also, your brake surface is pretty worn, you should ask us about what rims we have in stock!"

Although it isn't prefectly true, after they worked on it it is in great shape. You can definitely feel that there is a groove worn into the brake surface, however. Should I seriously be considering another rim at this point? I would just as soon ride this rim until the braking surface is worn paper thin :)

Maybe retire it from Cyclocross and use it for commuting only, assuming your commute is less demanding than your cross riding.

I don't have a hard and fast rule for replacement. I have never had a rim fail, which says to me that I replace on the conservative side and I have not had a defective rim. If I had to guess, I replace the rim when the sidewall is about 25% worn through. I would ride them on road bikes but I usually don't have any 26" road bikes.

1. Feel the brake surface with your finger. If it feels noticeably concave, it's probably time for a new rim.

2. Check out the spoke tensions with your fingers. If certain spokes are noticeably tighter than the opposing ones, or if your rim seems to be out-of-true in the direction of looser spokes, you have a bent rim. If that's the case, your rim is living on borrowed time.

In either case you can either plan a rim replacement or wait until the rim demands to be replaced. Rim demands usually happen when you're a long way away from your car.

i have the original front rim (main used brake) ON MY '89 dawes galaxy and i am about to replace that as it has considerably worn a deep groove in it

You have to be pretty conservative with rim replacement, and I usually recommend replacement when a noticeable concave shape forms on the braking surface. The best-case scenario is that the tire bead that is trying to push the rim sidewall outward bends a portion of it outward, which produces a noticeably loud scraping noise as the brake pads rub on it. Worst-case, the rim fractures along the circumference, blowing the tube and leaving you stranded. On a front wheel this can cause a pretty bad crash when you get a sudden blowout (most likely to happen on a steep hill too).

I put disc brakes on my commuter mostly because of rim wear issues (I live in the rainy PAC NW). A good life-span for road rims here when commuting in stop and go traffic can be 2-3 years.

I've had three wheels fail by cracking through the brake track due to wear. So far, the failures have been pretty benign. I was riding along and noticed a "thump, thump, thump" when I applied the brakes. Inspection showed a small section of the rim had bulged out and was hitting the pad. The cracks and the bulged section were small enough that the tube didn't fail and I was able to ride the bike home, but rather cautiously.

I wouldn't use my experience as a guide and I know I've been lucky. You may not be.

This isn't the one place you should skimp. A new rim is cheap, unless you have a carbon wheel. Rim swap takes all of 30mins if not less to complete.

Like others have said, if the rim's braking surface feels concave with little ridges, change it. They dont last forever. Before discs came into my life, I was getting maybe two years out of a rim. Your shop is probably giving you good advice. I have had two rims fail. One when I was topping up the air with a gas station hose-not an issue of over pressure either, I would only tap little blasts of air into the tube at a time and check with a guage. No this rim gave away cuz I was using it past its "best before" date. There I was kneeling down at the wheel, filling it, when ka-boom. I was deaf in one ear for ten minutes.

You certainly dont want a rim to fail like this while going down hill on a curve...

Agree with Retro-grouch's assessment and recommendation. A trip to the hospital can be worth a lot of wheel sets. A wheel failure will usually happen at the worst of times...downhill can put more stress on the rim. Open Pro for commuting are terrific. The new DT Swiss RR1.1 are equally great and have small drilled depth gauges that will tell you when the side wall is too thin.

When you get a new rim and spokes you might clean the pads of your brakes more frequently. Grit that gets on the pads can act as sandpaper on the sidewalls especially in the winter when the roads are sanded. I clean my brake pads weekly with an old tooth brush and a soapy solution. Good luck.

Open Pros should have a wear indicator. Is it not a black line that becomes visible? I know this is how Rigida/Alesa rims work.

You may want to look into a new set of wheels. For the price of a built set, it doesn't make sense to have a shop build them unless you need something special.

I am guessing they will stick you for at least $50 for an Open Pro. Labor will be at least $30. At least $20 for spokes. You can buy a brand new set for $200.

-Z

Sounds to me like you may need some softer brake pads. Suggest you see what is available from KoolStop.