Our pick of the best bike disc brakes.
1) Disc Brake Sets, InsReve NV-5 G3/HS1 Mountain Bicycle Bike | 2) Docooler Cable-Actuated Hydraulic Integrated Bicycle Front / Rear Disc Brake Set | 3) AFTERPARTZ NV-5 G3/ HS1 Bike Disc Brake Kit | 4) Avid Bb5 Road Platinum 140mm Disc Brake | 5) TRP Cable Actuated Hydraulic Disc Brake | 6) Shimano SLX M675 Mountain Bike Disc Brake | 7) Tektro Auriga Comp Rear 160mm Hydra. Disc Brake | 8) SHIMANO DEORE XT BL/BR-M785 Hydraulic Disc Front Brake 850 | 9) Shimano SLX BL-M7000 Disc Brake | 10) Disc Brake Sets, InsReve NV-5 G3/HS1 Mountain Bicycle Bike Mechanical Disc Brake Kit | 11) Avid BB7 SL Disc Brakes | 12) SRAM Guide Ultimate Disc Brake |
Originally found exclusively on mountain bikes, disc brakes are popping up on all types of bikes, at almost every price. It’s no wonder: With their excellent stopping power, superior speed modulation, and better all-weather performance than traditional rim brakes, disc brakes make huge impacts on your ride. But they can be heavier and sometimes challenging to maintain.
Don’t let that stop you from investing in them. Here are the parts of disc brakes you should know, and some quick fixes to their most common mechanical problems.
Types of Disc Brakes
There are two main styles of disc brake: mechanical (or cable-activated), and hydraulic.
Cable-activated brakes are what they sound like: The brake levers are attached to cables, which activate braking. The hydraulic version replaces the cables with hydraulic fluid in a fully sealed line. When you brake, the pressure forces the fluid to move into the caliper, pressing the pads against the disc.
Hydraulic Line Maintenance
If your disc brakes have a spongy and indistinct feel or fade on long descents, it’s likely due to bubbles in the line or contaminated fluid.
The fix is a brake line ‘bleed,’ where the old hydraulic fluid is flushed and replaced with fresh fluid. This is a skilled repair, best left to a shop mechanic. You need to use the right fluid, which is matched to your brake for proper heat management.
SRAM recommends bleeding hydraulic disc brakes every six months. Shimano’s official user manuals do not specify a service interval but does say to replace the fluid when it becomes discolored.
Disc Brake Calipers
Brake levers are attached by the brake lines to calipers located on both the front and rear discs. Calipers contain opposed pistons that sit on either side of the rotor; pressure from the brake line engages these pistons, which push the brake pads inward to contact the disc. The resulting friction slows the bike.
Disc Brake Caliper Maintenance
If your rotor doesn’t spin freely (resulting in rubbing, grinding, or squealing), the caliper might be misaligned.
Fix this by loosening the two bolts attaching the caliper to the frame or fork just enough so the caliper can move slightly side to side. Wiggle the caliper to make sure it moves freely, then pull the corresponding brake lever, hard.
This will clamp the caliper to the rotor. Hold the brake lever down to keep the caliper in place, meanwhile tightening the top bolt until snug. Tighten the bottom bolt until snug and then re-tighten the top bolt to torque spec, then the bottom one.
Disc Brake Rotors
Rotors come as small as 140 millimeters in diameter for road and cyclocross applications, all the way up to 205mm for downhill mountain biking. Generally, road and cyclocross use 140-160mm, XC mountain biking uses 160mm, trail riding uses 160-180mm (sometimes a mix, with the larger rotor up front), enduro uses 180mm, and DH uses 200-205mm.
Larger rotors are able to dissipate heat over a larger surface area, but are heavier, so you’ll want the smallest rotor you can get away with for the type of riding you generally do.
Disc Brake Rotor Maintenance
If you’ve adjusted your caliper but still hear rubbing, check your rotor: Sometimes, they warp from a hit or even just excess heat.
To find out if your rotor is warped, spin the wheel and sight along the rotor path. (Looking through the caliper provides a good reference.) If the rotor moves in a wavy fashion, like a wheel that’s out of true, it’s warped.
Often, but not always, warped rotors can simply be bent back.