Nobody ever won a race by going slow
However we have brakes on our bikes for a reason! Carbon fibre rims have always suffered from lower levels of braking power. However our new range of rims tries to improve that with the laser etched brake surface which improves braking in the wet and the dry.
Squeezing your brakes generates friction and heat. The laser etched surface on our rims helps generate more friction (and remove water) than you standard carbon rim and hence more braking power. Carbon rims are very poor at transferring heat away from the brake surface, which is why clincher rims in particular have suffered from heat related failures. Resins have improved considerable to withstand this heat up without the material also becoming brittle.
Your Brake Pads and Heat
The other half of the equation is the brake pads. Brake pads for carbon rims have to be softer and less abrasive or they will eat away the carbon surface far too quickly. Not only is heat built up in the rim under braking, but also the brake pads. The 3D laser etched brake surface on our rims actually generates more heat in the pads as part of the increased braking power that can be generated.
ANY rim and brake pad combination can have heat related issues with the brake pads. While this is less common on Al rims it can happen. Under long heavy braking the heat generated in the pads can cause “surface melting” of the soft pads and the brake pad become “glazed” and hard. This is different to just “fading” which will recover once the pads and rims cool down again. The glazed surface generates less friction, but is also less flexible so doesn’t work as well with the 3D braking surfaces on modern carbon rims.
This cause for reduced braking power can be easily identified by looking at the surface of the brake pads. If the pads look to have a different color to the braking surface, particularly towards inner areas of the pad’s surface, they are likely to be suffering from glazing.
The issue is easy remedied with some medium to fine sand paper to remove a small amount of the brake pad surface until the coloration disappears.
NOTE: Do not wait for braking performance to diminish – check your brake pads on a regular basis.
Brake Pads and Debris
Another major issue with brake pads and rims brakes is material build up around and in the brake pad surface. With Al rims is it not uncommon for little filings of Al to build up in the brake pads from the rim itself. Also dirt and grit can often embed in brake pads. With carbon rims, especially new carbon rims, any material that wears off the rim could build up around and on the brake pad surface.
Material build up can have two effects. Grit and dirt can be hard and sharp, and cause gouging of the rim surface. This material needs to be picked out of the brake pad or it will cause accelerated wear of the rim. Material from the rim surface itself is less likely to cause gouging of the rim, but it may affect the friction generated between the pad and the rim. Again keeping the pad surface and edges of your pads clean is a necessary part of bike maintenance. Even using a some sand paper as described above can help remove material build up and maintain your pads’ ability to generate braking power.
Brake Surface Condition
While it is not good for your brake pads to change color, and any unusual changes could indicate glazing or material build up than needs to be address – it is quite normal for new rims to experience some change in brake surface color.
The outside of most carbon rims will have some paint, or even mold release on the surface of the rim from manufacturing. When the rim is new this paint or external material is removed very quickly by the brakes and normally results in a change in color appearance along the braking surface of the rim.
NOTE: this early material that comes off the rim in the first few rides can build up on the pads as mentioned above.
It is even quite normal to see some small faint white marks on the brake surface of the new rim. This will likely disappear with some additional use.
Any minor scratches caused by debris in the brake pads, or minor change in color on rim brake surface is not a cause to stop using the rim. Just check the pads and act accordingly. Large scratches that are deep enough to cut the carbon structure DEEPER than 3D rim braking surface should however be checked. Likewise small surface discoloration is not a cause for immediate concern. However if the change in appearance does not go away, or gets worse, then the rim should be checked.
Bikes need to be looked after and maintained, just like a car. The ongoing performance of your brakes is a major safety consideration. Looking after the condition of your brake pads is a big consideration when using carbon rims. Brake pads are cheap, and if you ever need a replacement set just let us know at firstname.lastname@example.org and we will sell your some more good quality pads at a respectably low price.
If you are ever concerned that your rims have become damaged – do not hesitate to have somebody inspect them or send us detailed pictures to review.