9 Important Things To Know About Road Disc Brakes
Road bikes are evolving at a rapid pace and one of the most significant recent improvements is the incorporation of disc brakes. Rather than reviewing the commonly discussed benefits of road disc brakes, such as opening the possibility of using wider rims and tires for more grip, a smoother ride, less rolling resistance, fewer flats, and improved safety when rolling over uneven surfaces—this list covers all the essential technical points you need to know.
- Following the proper disc brake bed-in procedure is WAY MORE IMPORTANT than most people realize. When disc brake rotors or pads are new, it is critical to follow the proper bed-in procedure. This is a series of controlled stops that scuffs up the surface of the rotor and pad and deposits pad material on the rotor for increased friction. Doing this will result in much more powerful, smoother, and quieter braking. Watch the video below to see how it is done.
- Only use a mild soap and water solution to clean a bike with disc brakes. Harsh detergents and degreasers, as well as lubes and oil, can be absorbed by disc brake pads and result in drastically reduced braking power and loud brake squealing. Also, contact with these materials will irreversibly ruin your brake pads. So it’s also a good idea to avoid touching your brake rotors with bare hands in order to prevent oil or grease on your fingers from contaminating the rotor’s braking surface. That contaminated rotor then transfers the oil to the pads when the brakes are applied. Simply use a well-diluted mild soap and water solution to clean your bike and your disc brakes will keep working great.
- Hydraulic disc brakes automatically adjust for brake pad wear. As hydraulic disc brake pads wear down and become thinner, caliper pistons advance to compensate. While it isn’t super important to know how that system works, it is important to know that your brake levers will engage consistently throughout the usable life of the brake pad. Just keep in mind that if you pull your brake lever when the wheel is removed from the bike, the brake caliper pistons will adjust to a narrower position that doesn't include the width of the rotor. If this happens, you might not be able to get your wheel back into the bike unless you manually push the pistons back into place to make space for the rotor. This is best accomplished by using a pad spreader (the plastic spacers that come with new brakes) to push the pads and pistons back into the caliper. You can also install a pad spreader into the caliper while traveling with your wheel removed to prevent the pistons from advancing if the lever is accidentally activated.
- Hydraulic hose routing has no effect on braking performance. Gone are the days when selecting internal brake cable routing meant compromised braking power and increased hand effort at the lever.
- Disc brake bikes are often as aerodynamically fast as rim brake bikes, and in some cases, even faster. Bike designers are now integrating disc brakes into aerodynamic framesets that have lower drag than a rim brake bike. Well-known brands like Scott, Cervelo, and Specialized are already pulling it off with their 2018 and 2019 model year bikes; and like all things aero, it’s only going to get better in the future.
- While it is true that disc brake bikes are usually heavier than rim brake bikes, that’s not always the case. Big brand production disc brake bikes are already available that are under the UCI’s mandated 6.8kg weight limit for racing. We’ve even seen some custom disc road bikes that weigh less than 5.1kg! So use that advantage to beat your riding buddies both up the mountain and back down the other side!
- Hydraulic disc brake bleeding is easier than most people realize and it only needs to be done about once a season as a preventative maintenance service. We’ve developed levers and calipers with hydraulic passageways free of nooks and crannies that can trap air bubbles. This speeds and simplifies the bleed process. We’ve also developed the Bleeding Edge™ caliper fitting to make attaching the bleed syringe to the caliper quicker and cleaner than any other hydraulic braking system on the market.
- Disc brake rotor heat won’t affect tire pressure. All braking generates heat and that heat has to go somewhere. Some of the heat is absorbed by the air, but some of it is transmitted to places that can be a problem. When braking heavily on a long descent with rim brakes, some of the braking heat generated can transfer from the rim’s brake track to the air inside the tire, temporarily increasing tire pressure. Over-pressurized tires have reduced cornering and braking grip—which is not something you want when bike control is your top priority.
- Disc brakes can offer independent reach and contact point adjustments. Brake lever reach and contact point adjustment are both available on brakes like our RED eTap HRD units that use our HydroHC platform. You can get your levers to start their throw where they fit you best and also get the brakes to engage where you want them to. Like your brakes to engage right away? No problem. If you prefer to pull the lever back for a bit to prepare for braking without the pads dragging on the rotor, you can dial that in too.