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Common Questions About Carbon Wheels

by John Neugent

Tech articles | Commentary articles

John Neugent probably knows more about bicycle wheels than anyone else alive. Maybe more about bikes as well. He's spent his life in the bike business, at every level. He now owns Neugent Cycling, a firm devoted to delivering world-class equipment at the lowest possible price. If you are in the market for a set of wheels, please, check out John's site. He really knows his stuff. —Chairman Bill

John Neugent

John Neugent

I received an e-mail from a customer who asked a series of good questions about carbon rims. Below are his questions and my answers.

I don’t know if I can afford carbon rims (depends on the sale) but I have a few questions.

The only reason to get carbon rims (outside of the cool factor) is they can potentially make you faster because they are more aero. However, for most people, they don't really notice a difference unless they are pretty fast riders averaging 16-18 mph on flat ground. The faster you ride the more you get. IMO, if you are a normal rider averaging under 15 mph, lighter alloy wheels might give you more of an advantage on hills, the bane of most riders.

Alloy wheels

For some riders, a good set of alloy wheels are best.

1. Do carbon rims really require different brake pads and if so why? I’m not sure if they really need them or if the bike stores are just trying to sell some more pads?

Yes, they do require specific pads. Carbon doesn't shed heat like aluminum so it builds up in the rim. Carbon is also harder than aluminum. To deal with both issues you need carbon specific pads.

2. If someone doesn’t change brake pads and uses regular pads designed for alloy rims what happens?

You won't stop as well and you will melt and wear out the pads quickly.

Carbon clincher rims

You will want special brake pads for your carbon wheels.

3. I have seen with some carbon rims, they have a different weave or different resin like a basalt one on the braking surface that is supposed to take more heat. Do your rims have this?

Yes and no. Most carbon components have unidirectional carbon. This essentially looks like a matte finish although it may be coated with a shiny surface. Some people use a cosmetic layer of different weaves on the exterior (there are many options). Also, there are various treatments on the braking surface to mitigate heat. Mine do have those. The rims I use are safe up to about 430 degrees, but it's possible to get the rims hotter (going down a steep hill holding onto the brakes). If the rim overheats it will delaminate causing a bulge.  On tubular rims, it will overheat and melt the glue holding the tire on causing the tire to slide and rip off the valve core.

4. Are carbon rims more noisy? I have heard they sound loud when you are riding on them. Is this true, and what do you think?

Yes, they are. If you ever get a chance, watch a TT race with riders using deep carbon wheels and even the carbon aero bikes - they can be very noisy.

John Neugent was was one of the first to establish quality hand building in Taiwan around the turn of the century. He now owns Neugent Cycling, a firm devoted to delivering world-class equipment at the lowest possible price.