Condensed Answer: It’s not recommended to combine carbon brake pads with aluminum rims because the combination results in suboptimal braking and premature wear of the pads.
The Downsides of Using Carbon Brake Pads On Alloy Rims
- Suboptimal Braking
Since carbon isn’t very resistant to external abuse, carbon brake pads are softer and made of cork compounds. The softness of carbon pads results in substandard braking when the units are combined with alloy rims.
- Faster Failure Of The Pads
The softness of carbon pads results in an excessive grip which in theory increases stopping power.
However, in practice, the rim simply eats through the soft pad because aluminum is not as slick as carbon. The outcome is questionable stopping power and quick wear of the pad. In some cases, the pad may disintegrate.
- Contamination (Alloy To Carbon)
If a set of carbon pads is used on alloy wheels, it will no longer be safe to combine it with carbon wheels.
During braking, the pads shave off micro parts from the alloy rim. Carbon pads are soft, and thus small particles penetrate the outer layer and wedge themselves into the pad. If the same pads are then coupled with carbon rims, the aluminum fragments in them will scratch the rim and destroy it.
- Contamination (Carbon to Alloy)
If a set of carbon pads is first used on a set of carbon wheels, it will leave a residue when the user switches to alloy rims. The result will be poor braking.
Before going back to standard alloy pads, the user will have to clean the rim to remove the layer left by the carbon pad, or else the braking performance will not be optimal.
- Voided warranty
Combining an expensive set of wheels with brake pads that aren’t officially recommended by the manufacturer will result in a voided warranty.
Are there brake pads that work with both alloy and carbon wheels?
Some brake pads are compatible with carbon and alloy wheels. However, even those models do not allow the user to freely swap wheels. Once the pads have been used on one type of rim (alloy or carbon), they’re compromised and should not be used on a wheelset of a different material.
It’s also worth mentioning that multi-purpose pads are unlikely to offer the same braking power as pads engineered specifically for the rim in question.
What will happen if I use brake pads designed for alloy rims with carbon wheels?
Combining pads for alloy rims with carbon wheels is not a good choice either.
Carbon is a material that doesn’t absorb and dissipate heat. Or in other words, it can’t act as a heatsink. As a result, the wheels transmit a lot of heat to the brake pads when braking.
To fight this issue, carbon pads have much greater head resistance. For example, SwissStop alloy pads have 160°C heat resistance whereas that of their carbon pads reaches 300°C.
If pads designed for alloy rims are combined with carbon wheels, the rims will melt the pads during long descents. Then, the user will lose the ability to brake.
Can carbon pads damaged by alloy rims be fixed?
It’s possible to put carbon pads back in shape for a carbon wheelset after using them on alloy wheels by doing the following:
- Remove the large aluminum pieces that have penetrated the pad with an awl and/or tweezers.
- File the upper layer of the pad to eliminate the small aluminum debris too.
How can I tell if my brake pads are designed for aluminum or carbon wheels?
Carbon pads are usually odd colors (e.g., blue, yellow) whereas pads designed for alloys are often black.
Also, if the pads are for carbon wheels, there will be a small text on them saying “carbon”.
Naturally, alloy pads will have an “alloy” label. However, this isn’t always the case.
FAQ: I have two sets of wheels – carbon for race days and aluminum for training. Can I use the same pads for both sets?
One may be tempted to use one set of pads for both wheelsets for convenience and time savings, but the answer is no. To avoid damaging the pads or the rims, it’s recommended to replace the pads when switching wheels.
In most cases, this shouldn’t be a problem because most people do not compete very often and thus wheel swapping isn’t done on a daily basis.
Summary: What You Need To Know
- Carbon pads are softer than brake pads designed for alloy rims. As a result, the braking experience is suboptimal. Also, carbon pads don’t last as long because aluminum is harder on the pads than carbon.
- If carbon pads are combined with alloy rims, metal fragments from the rim will get into the pad. Thus, if the user returns to a set of carbon wheels, the rim will be damaged severely.
- If a carbon brake pad has been used on an alloy rim, and the user wants to go back to carbon wheels, it will be necessary to clean the pad deeply before making the switch.
- If the user combines brake pads designed for alloy rims with carbon wheels, the pads will very likely melt during descents because carbon doesn’t act as a heatsink.
- For optimal performance, it’s recommended to use brake pads designed for the rim in question.