August 10 2010 by Jason Fogelson
After tires and wheels, I would have to say that brakes are the most critical component on your motorcycle. So, we should spend a little bit of time understanding brakes so that we can get the most out of them.
Most modern motorcycles, in fact all current Harley-Davidson models, arrive from the factory equipped with disc brakes front and back. A few entry-level bikes and scooters still have drum brakes in the rear, but disc brakes are pretty ubiquitous. You may have a single disc up front, or you may have dual discs. It's a matter of function, design and cost. You'll get more stopping power from dual discs, but you get a clearer view of the front wheel (on one side, anyway) with a single disc. And a single disc brake is a less-expensive setup, obviously.
A brake system consists of some key components, each of which can be modified and upgraded, and which must be maintained in order to work properly. From one end of the system to the other, there are the brake levers and pedals, the brake cylinders (master and slave), the brake lines, the calipers, brake pads and the discs. Motorcycle braking is usually a hydraulic system (there may be exceptions, but they are rare). In a hydraulic system, a fluid under pressure causes an action when the pressure in the system raises or lowers. In the case of a motorcycle brake system when you pull back on the brake lever (or press down on the brake pedal), brake fluid pressure is transmitted through the master cylinder to the brake lines to the brake caliper. The brake caliper straddles the edge of the disc. Brake pads line the inside of the caliper, held just fractions of an inch off of the surface of the disc. When fluid pressure in the hydraulic system rises, a piston (or pistons) on the caliper forces the brake pad into contact with the disc. The caliper clamps down on the disc, and friction causes the disc to slow and eventually cease its rotation. The disc is attached to the wheel, so the wheel slows and stops, too, and the bike hopefully does the same, assuming that traction is maintained. Simple, right?
As simple and brilliant as motorcycle braking is, there are several points in the process that are subject to failure. The most common braking problem is loss of pressure in the hydraulic system. Loss of hydraulic pressure can be caused by air in the brake lines, contaminated brake fluid or a failed component somewhere in the braking system. If you're mechanically inclined, you can tackle some braking problems on your own. Motorcycle brakes are not much different than automotive brakes, so most of the skills you've developed working on your car will transfer. If you're not confident in your abilities, don't do your own brake work, at least not without help from an expert. Brakes are even more critical for your motorcycle than they are for your car, and you don't want to mess them up. There's little margin for error.
Let's talk upgrades.
One of the coolest custom-looking upgrades you can make to your motorcycle can also deliver better brake performance and feel. I'm talking about stainless steel brake lines. Most stock bikes come with rubber or synthetic brake lines, which do a fine job of transmitting hydraulic pressure. But stainless steel lines are firmer, and are less likely to get "mushy" with heat and repeated use, so they deliver more consistent performance over time. And they look way cooler.
Replacement levers and pedals, either from your original manufacturer or from the aftermarket, are another great part that can improve the looks and function of your braking system. Matching the hand control to the size and strength of your hand will make braking easier and more effective. Same thing with the foot control and your foot. This is the kind of personalization that will really make your bike your own, and will make you eager to ride more.
Brake calipers and discs are also ripe for upgrading. Specialty manufacturers like Brembo and Performance Machine concentrate their expertise on braking, and make high-performance calipers and rotors to fit a wide variety of bikes. It may even be possible to go from a single rotor to a dual rotor system on your bike, even if the manufacturer never offered the option from the factory.
Brake pads are a wear item, and need to be replaced on a regular basis - usually every 10,000 miles or so. As you may have guessed, there are dozens of choices for brake pads, with different compounds, thicknesses and grabbing power available to match your bike, riding style and stopping needs.
If you know nothing else about brakes, I hope that you know this by now: Your motorcycle brakes are a critical safety component, and they demand your attention and concern. Pay a little bit of attention to your brakes now, while they're working well, and your brakes won't let you down when you need them most.