Brake Pad/Aluminum Pack—Cleaning Maintenance vs. Adjustment
brakes, there will actually be very little adjustment and much more
maintenance. Once the brake itself is centered to the rim and the brake
shoes are likewise centered, the brake will tend to stay where you put
it—assuming you remembered to properly tighten everything! Whereas many
stem and seatpost bolts are tightening carbon fiber components and you
must be aware of the torque specification on those parts, these basic
nuts and bolts are generally pretty durable and can be tightened as
tight as you are comfortable turning. Just remember how bad a day it
could be to have a brake or a brake shoe fall off.
One thing will change as the pads wear: as the brake arms arc further to connect the thinner brake shoe with the rim, the road brake will hit a spot progressively higher on the rim and a cantilever or v-brake will hit a spot progressively lower on the rim. In the photo below, the bottom brake shoe has a small shelf beginning at its bottom edge. Eventually, it will be necessary to re-center your pads accordingly.
Just as the derailleur cables need to be
periodically lubricated, so do the brake cables. On a road bike with
road caliper brakes, you can remove the wheel and pinch the brake pads
fully together and create enough cable slack to pull the rear section of
cable housing out of the top tube “cable stop.” That portion of the
cable/housing interface can now be lubricated. The chain lubrication
works just fine. On the mountain bike, once the rear brake is
disconnected there should be enough slack to remove the housing from the
frame stop without removing the wheel. Again slide the housing away
from its normal location to lubricate that portion of the brake cable.
In most cases, the front brake is a full length of housing, and
lubrication is more difficult, but is also far less likely to be
After the cable lubrication is completed, it is time to look at the contact faces of the brake shoes and the rim. These two surfaces wear each other—the brake shoes actually take away small amounts of rim at the same time the rim is wearing away the brake shoe. Older rims will show this wear by having formed a concave brake surface. Some riders have completely worn through their rim's braking surface and have had the tire blow the top of the rim away. A truly memorable moment! Many new bikes and rims have wear lines or dots to help cue you into this impending doom. When the indicator is gone, it is time to replace the rim or wheel.
All of this aluminum has to go somewhere, and much of it will be packed into the brake shoe itself. Inspecting the brake shoe, you may see a silver smear on the face of the shoe. Often, this aluminum paste begins to re-gather into tiny pellets in the shoe. Once a pellet forms, it will cut into the rim more aggressively and gather even more aluminum in a somewhat frightening variation of the snow-ball effect. Rim and brake shoe maintenance is a matter of cutting the aluminum glaze from the shoe and cleaning the shoe compound from the rim. A moderately aggressive file—I actually like a larger than average chainsaw file—works well for cleaning the aluminum from the shoe. If larger pellets have formed, you may have to ‘dig’ a little to get them out. For the rim, the best thing is a clean and dry Scotch-brite pad. Funny enough, the 3M brand pad really does work best—it is just a little more abrasive than the knock-offs. You can cut the scrubby into little squares and really buff the build up off of the rim. My friend Les Welch would actually cut brake shoe sized pieces and slip them between the brake and rim and go out and do circles while holding the brake. Disclaimer: do not ride down any hills with scotch-brite pads in your brakes! Inspect the rim for dings from the last rocks that you hit, or even small cracks radiating out from where the spokes seat into the rim.
When you check your brake shoes for glaze also check them for wear. First, notice that the brake shoe has vertical grooves in it—if these groves have worn away then it is really time to replace the shoes. These grooves are much more for wear indicating than for any kind of material movement or cooling effect. Second, notice whether or not the shoe is wearing in an even pattern. If the shoe is too low to the rim, the portion not hitting the rim is not being worn, and will show as a ‘shelf’ at the bottom of the shoe. If the shoe is too high on the rim, the top of the shoe will not be getting worn down and will begin to project further out from the rest of the shoe—a high shelf. In the picture above, notice how the third shoe down has a diagonal wear pattern—here is your cue that the pad needs to be re-aligned. Ideally, the brake shoes should get a quick look anytime you have the wheel out of the bike. Otherwise, every two to three weeks of riding time is a good check cycle. Often, I will hear a more metallic sound as I apply my brakes and that is my cue to clean those shoes!
Brake shoes are no longer leather or rubber as they once were. The newer ‘synthetic’ compounds loose their volatile component over time and the brake shoes become very hard. It is a good idea to replace brake shoes every other year, whether they are worn out or not. The new, more supple pad will stop you better.