Published on December 15th, 2016 | by Luke
Ask a Mechanic | Bedding In New Disc Brake Pads
Michelle says, “I just bought new brake pads, but my braking performance is worse than before. What’s wrong?”
Life, and mountain biking, is in the details. Paying attention to the little things, like disc brake pads, will go a long way towards enhancing your riding experience and maximizing your fun factor. Properly bedding in new brake pads is crucial for your brakes to be fully functional.
If you’re buying new pads, keep in mind that organic/semi-metallic/resin pads are softer and tend to be quieter. They offer more initial bite, but fade faster than metallic pads on longer descents. Metallic pads last longer (especially in muddy conditions), handle heat better, and resist fade better under heavier braking loads.
When new, rotors and pads have imperfect surfaces that appear rough on the microscopic level. By bedding in the pads and rotors together correctly, a thin layer of brake pad material is slowly and evenly transferred to the rotor. This partially fills in the rough surface of the rotor and creates a geometric match between pad and rotor for optimized friction and interface.
Here’s how to break in your new pads. First, pads and rotors must be clean; be careful not to touch the pad surface with your fingers when unpacking and installing them. Clean rotors with a non-residual cleaner like isopropyl alcohol. Once the rotor is clean, do not touch the braking surfaces.
After the pads are installed, get on the bike, pedal up to speed, and then gently grab the brake levers, slowly and smoothly applying pressure until you almost come to a stop. Do not stop quickly, but let the brakes drag you down to a slow walking speed. You want to heat the pads enough to lay down the transfer layer of pad material evenly across the rotor surface, and that’s all.
Complete this slow stop process 10 to 20 times, and you’re good to go. Braking too hard and thus generating too much heat will build up an uneven transfer layer, resulting in noisy brakes, wobbly-feeling rotors and underpowered braking. Coming to a complete stop will also lead to uneven pad material transfer, so this should be avoided as well.
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