Still more....
The biggest disadvantage of disc brakes is that they are exposed to dirt. Dirt and dust between the rotor and pads can wear the disc quickly. If the rotor is too thin, it cannot dissipate the heat and in extreme situations it can crack; rotors that are worn too much must be replaced.
Front disc brakes sit in relatively clean air, but rear discs are exposed to all the dust and debris thrown up by the front tires. This is why rear disc brakes often wear faster than front disc brakes, even though they are only doing a small percentage of the braking.
Anti-lock brakes work best with disc brakes because they release quickly and smoothly. Changes to shoe design and placement have helped drum brakes release quicker, but discs are still better. For this reason, and for maximum stopping power, you find four-wheel disc brakes on many vehicles.
I personally prefer front discs and rear drums. I still get all the advantages of discs on the front and can stop very well, but rear drum brakes are not exposed to the dust so they wear much slower under many conditions. Less rear brake maintenance leaves more money in my pocket. Just don't ask me to go back to four wheel drum brakes - they were scary!
Jim Kerr is a master automotive mechanic and teaches automotive technology. He has been writing automotive articles for fifteen years for newspapers and magazines in Canada and the United States, and is a member of the Automotive Journalist's Association of Canada (AJAC).
