Disc brakes do a few positive things for riders. First, they make it possible to brake later and with more confidence. Second, they make weather, wet or cold, less of an issue. The result is a bike you will descend on more quickly and will ride on more days of the year.
But many riders miss the key differences between a disc road bike and one built for rim braking. They believe it’s just a matter of moving the brake caliper, or as we hear the request all the time, “Can you just weld a disc tab into my older frame?”
Not only is the type of brake different, but the spacing of the rear end, essentially the axle width, is wider. Because disc brakes free us from tire width constraints, most riders will choose clearance for wider tires, and thus the bike’s chainstays will get slightly longer.
The front end of the bike also sees some adjustments. Head tube angles change to keep those wider tires from overlapping too much with your toes. Fork rakes then change to make the bike handle correctly.
Designing disc brake road bikes is about much more than simply changing the location of the brake caliper. The stopping forces associated with disc brakes are torsional, rather than symmetric, as with rim brakes, so the construction of the disc dropout needs to be stronger than a conventional dropout and the asymmetry that results needs to be counterbalanced with other aspects of the frame, like chainstay diameter and wall thickness, as well as seat stay diameter and compliance.
Seven Cycles thinks about all of these things.
Another thing to consider is weight. Stronger dropouts and heavier brake calipers make disc bikes heavier than the performance road bikes they’ve built over the decades. So, they’ve also developed new build techniques to reduce extraneous weight in the frame, so that the weight cost for going disc is offset to some degree and the bike remains competitively light. Advanced tube butting techniques, more aggressive machining of the tubeset, and some clever parts choices are the ways they deliver a lighter disc road bike.
All of Seven’s road bikes are available in disc and rim brake configurations.
Original content and images provided by Seven Cycles.