My mechanic claims that carbon wheels get «soft» after a few years of riding, and cannot be serviced back to its original quality. It manifests by brake disc rub in the front and he showed me how the wheel flexes by pulling it sideways at standstill.
The wheels are mid-tier with decent hubs and lacing, is 7 years lifetime to be expected?
by 19quiz76
4 Comments
What is his take on these new carbon frames?
Your mechanic is an idiot. Get a new one. Only a hub made of wet spaghetti (technical term) would be able to flex enough to cause disc rubbing. If this moron thinks that lateral flex in a wheel could affect the location of the rotor relative to the caliper, he’s not fit to build lego, let alone bikes.
Fork flex can cause disc rubbing, no doubt about it, but lateral rim movement cannot cause rotor rub.
Your mechanic sounds like an idiot. How would a softening rim effect the hub/rotor/axel? Think about it… just like, take a second and analyze what they said to you… It doesn’t make sense.
Now, do carbon rims ‘soften’ over time? Well, yes and no. First of all, carbon fibers themselves are extremely strong and resilient. More so than almost any other structural material.
However, we are not building things with carbon fibers, we are building things with a carbon fiber *composites*. Those composites consist of about 70% epoxy resin: glue. Carbon fiber wheels and bikes are mostly glue. Now, carbon fibers themselves haven’t really changed much in the last 30 years. The carbon fiber bikes from the early 2000’s were made from similar carbon fibers we are building with today. What has changed a lot in the last 30 years is epoxy resin technology. The material science of this glue has advanced leaps and bounds in the last few decades.
Old carbon fiber components would go ‘soft’ or brittle, yes. Stress, UV exposure, oxidation/corrosion, water, high temperatures, low temperatures, were all concerns with older carbon fiber bikes. But, not because those conditions effected the carbon fiber (which again, hasn’t really changed) but because it effected the epoxy.
Years ago, resin would go brittle and discolor if exposed to UV rays. So, if you were riding your bike outside, your bike had a shelf life.
That is not the case anymore. Resin technology has advanced sufficiently that longevity is no longer an issue with carbon fiber components. Avoid point loads, impacts, excessive heat, and abrasion, and your wheels will last a decade, no problem at all.
That said, carbon fiber production needs to be done well. Material defects can lead to catastrophic failure. Buy from a reputable manufacturer, of which, there are many.
Your mechanic is wrong.
Well made carbon products have infinite fatigue life.
Unless there is physical damage to the rim there is no change in rim stiffness.
You could have things loosen up at the spokes causing more flex.