If you’ve looked at a new bicycle recently, you’ve probably seen a pair of shiny rotors hanging off the hubs. And if you’ve been on a trail ride recently, you’ve probably heard a variation of the ear-splitting squeal of metal-on-metal. You may be telling yourself stuff like, “whats wrong with my Paul canti’s?”, or, “if I get disc brakes will everyone think I’m cool again?”, or, “I don’t think I need this but I know I definitely need this.”
The most popular selling point of disc brakes is stopping power, which you’ve probably heard before. And it’s true! Usually this means that you get to pull your brake lever with less force, or your lever requires less throw to bring the bike to a controlled stop. This is a blessing off-road, where traction is limited and obstacles abound. While increased stopping power is obviously a plus, the real benefits of disc brakes are in the wheels.
Conventional rims must have a brake track along the sidewall to allow for stopping (duh). As the brake pads contact the rim, they remove material from the braking surface. Because of this, conventional rims have a finite wear life, and are constrained in design by incorporating a brake track. By moving the braking surface onto a rotor, the disc brake rim is not subject to wear. Additionally, disc brake rim design is not constrained by the conventional brake track. This allows rim manufacturers to design stiffer, lighter rims, that wont wear out with use, (although knowing you, they’ll be dented within a month).
So now you have better stopping power (sick!), and stronger, lighter wheels (thanks!), what more could you want? Oh, right, you love 650b conversions. Disc brakes allow for simple changes in wheel size, allowing you to run any tire that will fit in your bike. With the industry on plus-tire overdrive, and modern bikes getting more and more clearance, things can get real shreddy real fast. For example: on a humble SOMA Double Cross Disc one can fit 650b x 48 Compass tires or even some slick 26x3s! No fake!
Well this is all great and good, indeed it is downright revolutionary, but what about that damned squeal? Disc brakes generally make more noise than rim brakes. The quietest disc brake will still make a rasping, scraping noise, especially under hard braking. “Bedding” disc brakes is absolutely essential to quiet operation: this is the process of transferring an even layer of brake pad material onto the rotor. Squeal occurs when this bedding layer is uneven, causing the pads to alternately skip and bite, creating resonance in the rotor and curse words from any humans nearby. Perfect bedding is hard to achieve! Most disc brakes will end up squealing some amount at some point in their lives.
Finally, we come to cable vs. hydraulic systems. Hydraulic disc brakes are the bee’s knees. They offer insane modulation and power (think one-finger braking), self adjust for pad wear, and tend to squeal less. However, they require in depth maintenance (bleeding and replacing fluid), can fail at low temperature, and are rendered useless if the hose is breached by say, a sharp rock. Additionally, the rubber seals have a finite lifetime (usually a few years), leading to system rebuilds or more frequently replacement of the whole system. For us, there is no question that Shimano hydraulic disc brakes are the best. They use mineral oil which is much easier to work with than SRAM’s DOT fluid, and setting them up is actually fun, instead of inducing murderous rage. Tektro also uses mineral oil (nice!), while Formula and Hayes use DOT fluid (boo!).
Cable actuated disc brakes address many of the shortcomings of their hydraulic brethren, but are more prone to squeal, require frequent pad adjustment, and their lever feel is very dependent on the cable housing. Compressionless cable housing is a must for good lever feel, and bedding must be executed with fanatical commitment (we like SwissStop’s instructions at the bottom of their product page). The most adjustable mechanical disc brakes are the Avid BB7, and the Paul Klamper, due to their dual external dials. A favorite of ours is the TRP Spyre and Spike, which mimic the actuation of a hydraulic system, though require hex wrenches to adjust.
Disc brakes are quickly becoming the standard in the bicycle industry. To us, they promise stronger, lighter wheels, and the freedom to change wheel size. Disc brake systems are only going to improve with time, and we look forwards to seeing the benefits of disc brakes come to fruition. So, do you need disc brakes? If you ride off-road, carry a lot weight, or want to freely experiment with different wheel sizes, then yeah, go for it! If you’d like to continue this conversation, come on in and visit us, really, we love talking about this stuff.
