Rim wear: when is it too much?

By now you should all be familiar with the REAL advantages of a set of wheels built from available components: parts can be replaced. So, the next question is when to replace parts? For spokes it is easy, as when one breaks, you get it replaced, at the second one, you go for a full rebuild as it means all the spokes are fatigued.

What about rims? This is a more delicate subject and potentially more hairy. Some rims have wear indicators, tiny grooves that disappear upon wear of the brake track as a warning sign, others simply don’t. In fact most don’t have any wear indicator. If you allow a rim to become too thin, this happens

wheel

A Mavic Open PRO that didn’t make it…

Embedded image on Photobucket

… and an H plus Son TB 14 that made it despite extreme wear…

The rim side wall, pressured, by the clincher tyre, bursts out in a bang. This is typically a sudden event, which can happen while you pump up your tyres in the morning, or while you are out on a ride. Needless to say, it is very dangerous. After a long cold and wet winter, chances are your rims have taken quite a shave and it is probably a good idea to have a look at them. This particular rim had only 0.7 mm of alloy left at the point where it failed, but whenever the wall thickness reaches 1 mm, you are in uncharted territory and anything can happen. It is often difficult to assess if a rim needs replacement and all the advice I can offer is in the form of a few golden rules:

1) If you feel the rim is slightly concave and you are in doubt, get it replaced

2) Always inspect your rims after long spells of riding in wet weather

3) Keep your rim brake track and your brake pads clean, debris wear rims at an exceptionally fast rate

4) Replace brake pads as needed, don’t wait for them to wear too thin

5) Consider cable operated disc brakes for your next commuting/winter bike. The technology is mature even for road bikes

 

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5 thoughts on “Rim wear: when is it too much?

  1. Interesting. My rear Fulcrum R5 has covered around 7500 miles and I think it’s due for replacement, but there’s no rim wear indicator and I’m really not sure! I’m quite “brake happy” too. It may be time for a closer inspection before something like that Mavic happens! 😮

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    • You can measure the wall thickness with a gauge… new rims are around 1.3-1.4… if you are under 1 mm it is uncharted territory. Most rims will fail at at around 0.7 mm in my experience, but I have seen a TB 14 surviving when it was only 0.5… so it’s down to luck, really

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