All About Disc Brakes

I suppose it makes sense that the popularity of disc brakes has trickled down from the whole motocross scene. After all, they do provide the most reliable and most powerful stopping power in any type of weather and any terrain, which makes them perfect for trail riding. Plus, their power is not affected by landing hard or having a bent wheel. They use rotors which are attached to the wheel hubs and calipers attached to the frame with specialized shoes (brake pads). The shoes are made from ceramic or metallic based material which are, in turn, less affected by heat, wetness, and mud. Also, some disc assemblies use hydraulic fluid (rather than cables) for even better stopping power and reliability.

So you wanna know about disc brakes on mountain bikes, huh?

Well, here’s the Down Low……..

There’s 2 types of setups:

1. Mechanical Disc Brakes

This style uses the same cable setup that’s found with traditional bike brakes.

Advantages: light weight, easier maintenance, easier installation and adjustment, and you can get cables at any bike shop and alot cheaper than hydraulic lines.

Drawbacks: cablestretch ( causes spongy feel, more frequent maintainence, reduces stopping power), this setup is also going to be vulnerable to dirt, rust, and junk building up that can lock up your brakes. With proper maitenance, all this can be avoided.

2. Hydraulic Disc Brakes

This style uses a closed system of reservoirs and hoses containing specially designed hydraulic fluid. You squeeze the brake lever, a plunger pushes the fluid into the caliper, the pads squeeze the rotor, and you’re bike stops.

Advantages: hydraulics uses a sealed system so things like water, dirt, mud or debris have no affect on stopping power. This makes them virtually maintenance free once you have them installed correctly. You get an encredible grip at the rotor and a wicked smooth feel at the lever.

Drawbacks: Professional set up and frequent inspections are mandontory. a small leak or air bubble in the system can cuase complete power loss. It can be such a delicate process so… I always recommend having a professional do it.

　NOTE: Even though disc brakes work awesome on extreme terrain, it’s always important to keep them properly maintained. They’re the most important part of your bike and, the first and foremost thing when it comes to safety so I always recommend having them professionally installed and maintained, unless you’re that confident in your abilities. Another piece of advice would be, DO NOT squeeze your brake lever when you remove the wheels, the pads will contract and then you’ll never get the wheel back in.

Here are a few hints to help maintain your discs. Diferent setups may require “model-specific” maintenance and may not be listed here. For that……. I do apologize. There are, however, tons of instructional videos online for self-maintenance.

Cleaning and Inspecting Your Rotors

Loss of braking power can be caused by rotors that are cracked, warped, dirty, or any other sort of damage really. If you find cracks or dingers on your rotors or if they are overly wobbly (more than 1mm), then you should replace them immediately. Oily and dirty pads or rotors can also cause loss of power. Clean them ONLY with isopropyl alcohol, other degreasers or cleaning agents can contaminate or damage the rotors or pads. If paower is not restore then you should replace them immediately.

If they’re noisy or squeeky, check all the bolts attaching the calipers to the bike and the bolts on the rotor. Noise can also be caused by dirty pads, keep em clean.

To see if your rotors are warped, spin the wheel and watch as they rotate next to the pads, as long as they don’t rub, they’re good. If they do rub, I usually tap the warped spot with a rubber hammer. Be careful, you don’t want to overdue it, you could make them worse. And remember, don’t touch the actual braking surface of the pads or the rotors, the oil from your hands can contaminate them and decrease stopping power.

Lever Reach

With hydrauloic setups, if the lever feels spongy or pulls all the way to the handle-bar, there might be air in the system. Probably time to bleed it. Inspect all of the hydraulic hoses and fittings for leaks. If you find a leak, bring your bike to the shop immediately.

Checking and Removing Your Brake Pads

Inspection: If your pads are thinner than a nickel, you need new ones in a couple of rides. If they’re thinner than a dime, change them immediately. Put them back just the way they came out and make sure the new pads sit completely inside the calipers.

Removal: With the wheels removed, use your fingers or pliers to grab the tabs extending below the inner brake pad. Pull the pad(s) straight out and toward the center of the caliper body until it come free. Magnets and springs may be incorporated in your particular model, those will come free also. Save them, you’ll need them for replacement.

Preventing Brake Drag

Your rotors have to be centered within the calipers in order to eliminate drag and noise, and allow for maximum stopping power.

If your setup uses washers or shims on the caliper bolts, just add or remove to center the caliper.

Some systems use a 2 part bracket. First, loosen the 2 centering bolts holding the caliper to the mounting bracket, then squeeze the lever and tighten the bolts. It also helps to gingerly shake the caliper body, allowing it to come to a centered position, before tightening the bolts. Another nifty little trick is to stick business cards between the pads and rotors before applying brakes, this also helps to center the calipers.

And of course, the last thing to do is give the wheels a spin and check for rubbing.

Pre-Ride Inspection For Disc Brakes

1. Check brake rotors for dirt, debris, and fluid. Clean them ONLY with alcohol if need be.

2. Give both wheels a good spin to make sure the rotors are straight and not rubbing.

3. Squeeze brake levers to check for solid pad contact with rotors and proper lever reach.

4. Always inspect all your hydraulic hoses and fittings for leaks before every ride.