Road Bike Disc Brakes: An Overview

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There is a new standard in brakes on the road bike. It has even entered the professional peloton. It is disc brakes for road bikes. You may be asking yourself, is this really necessary? We’ve been riding road bikes with regular rim brake calipers for years. Well be prepared to make the change if you want better brake performance in all riding conditions. The same reason why mountain bikers have made the transition to disc brakes is the same reason you should make the transition on the road.

Road disc brakes require a different design for the front fork.
Shimano’s hydraulic disc brakes are shown here. Photo by Donald West

Disc brake rotors provide a consistent braking surfaced better brake modulation. Disc brakes are more powerful and remove issues of beefing up the rim surface to handle braking forces. Disc brakes remove any issues you may have with carbon wheels, including confusing brake pad choices. The removal of the brake surface on wheels will allow rim manufacturers to make lighter rims. There is less force that needs to be applied to the brake lever in order to stop the bike, which decreases rider fatigue.

Disc brakes also allow bike designers to increase clearances of tires without dramatically changing frame design. No more having to open brake calipers to allow for wider tires on road bikes or open brake calipers for cyclocross bikes. This opens up the door for wider rims and bigger high volume tires that can improve traction and braking performance.

Front forks require a new design to accomodate road disc brakes.

The only downside to disc brakes is they require you to have a disc specific frame and wheels. There is a slight increase in the weight of the disc bike. You also need to consider that these brakes require more mechanical know how. Hydraulic disc brakes use either dot 5 brake fluid or mineral oil to actuate brake calipers, just like the brakes on your vehicle. Finally, there will be issues with compatibility.

There are a myriad of new standards for disc brakes that are available, so swapping components between bikes will lead to some headaches. One of the new standards we will likely see are thru axles front and rear on road bikes. It is likely that we will see very few 9mm quick release axles in the near future. Thru axles will improve handling performance by increasing the strength of the connection between the wheel and the frame. Also, riders will be less likely to misalign the wheel in the frame during the wheel installation process. Finally, disc brakes are going to be more expensive than their mechanical counterparts.

TRP's cable actuated hydraulic brake.
TRP's cable actuated hydraulic brake.

There are several choices for riders considering changing over to road disc brakes. You can use hydraulic disc or cable actuated disc brakes. Each of the major component companies, Shimano, Sram, and Campagnolo, now offer disc brakes for road bikes. Shimano offers a hydraulic disc brake and electronic shifting option. Sram offers hydraulic disc brakes and mechanical shifting options. TRP offers a cable actuated hydraulic disc brake. SRAM/Avid allows riders to avoid hydraulics all together with their able accepted mechanical disc brake.

SRAM's Force Hydraulic Disc Brakes provide incredible stopping power.
SRAM's Force Hydraulic Disc Brakes provide incredible stopping power.

Most riders will be able to run 140mm rotors for their bikes or a combination of 140mm and 160mm. There will be 160mm rotors available for more braking power. Rotors are mounted to the non-drive side of the wheel for obvious reasons either by 6 bolt standard or center lock attachment. The calipers mount to the frame in two standards, a mount similar to a post mount you’d find on mountain bikes, or ‘flat mount” calipers. Flat mount calipers are likely to be the new standard for road bikes due to their lighter weight and more compact design.

So there is the breakdown of the new trend in road biking. If you are willing to make the investment in a new frame and wheels, I believe you will have another excellent option for your exploration of your local roads. If you don’t feel that it is necessary to change over, there are still plenty of options for riders who want to stay in the mechanical brake caliper world.

Donald West is the owner of Bicycle Motion, a mobile bicycle repair business in Utah County. Find them at bicyclemotion.com.

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1 COMMENT

  1. For those of us with new bikes that have disc brakes, it would be great to see an article on what basic maintenance we should regularly be doing on them and what longer term/seasonal maintenance should be done prior to winter storage or before beginning a new season.

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