Disc brakes are one of the most significant advances in mountain bike history. It only takes a spin around the block on a bike equipped with old-school cantilevers to be reminded of how lucky we are to have the stopping power and control that modern disc brakes offer. We asked Fabien Barel, Brake Authority's R&D manager (as well as two time Downhill World Champ), about how disc brake pads are made.
What are disc brake pads typically made of?
How are they made? Can you explain what “sintered” means?
Brake pads can be divided in two main categories: organic and metallic sintered. The materials which compose the compound are merged together during the manufacturing process thanks to a binder. This binder is in resin for the organic pads, or in metal for the metallic sintered pads. The sintered pads are lot more resistant to high temperature whereas the resin has a tendency to melt and burn which results in a drop in the braking performances at high speed. Plus, the sintered pads last longer.
Most riders are familiar with how hot rotors and calipers can get after a long downhill. What types of temperatures have you seen during testing? What is the effect of high temperatures on braking performance?
STEP 1: Powder mixing
Sintered pads are manufactured using powders.
The friction product contains at least 10 different constituents (copper, bronze, iron, ceramic, graphite…).
Each of these constituents has a key role when the pad is in contact with the rotor (comfort, noise, performance).
STEP 2: COMPRESSION
Once mixed, the constituents become a friction mix which is then compressed using a tool that gives it its definitive shape.
STEP 3: HEATING AND SINTERING
Next, the result is placed on a metallic base and placed in a high temperature oven.
That’s the sintering process: one constituent of the mix melts and attaches the compound to the base..
STEP 4: FINISHING
The pad is finally rectified, checked and packed.
Sintering = technology that allows the transformation of metallic powders into metallic compounds.
What is “bed in”? Why is this important?
We've seen temperatures of 125 °C recorded with the laser captor during the DH testing sessions.
Extreme heat during braking can cause what riders typically call 'fading.' This is the drop in braking performance that will cause a longer braking distance.
What makes one pad better for XC while another one is better suited for DH?
When they’re new, rotors and pads have a slightly rough surface, which decreases the braking performance. That’s why bed-in is always necessary to get the optimal performance from the brake system. The bed-in period allows any roughness to disappear in order to have pads and rotors perfectly flat. Therefore, the contact surface between the compound and the rotor is maximum and braking is more efficient.
In our R&D lab, we put together different compounds for different uses. In fact, for each use we have a specific pad. It’s important to choose the right pads depending on your discipline. If you just ride along with your MTB, there's no need to get pads for DH racing for example, as they’re designed to be efficient at high speed - they'll still work at slower speeds, but that's not their intended purpose. That’s why we’ve developed the Ceramic, oriented towards DH racing, and the Burly, which is more suitable for leisure or “non professional” use.