Sure, many road riders are still resistant to disc brakes. But judging by the crop of 2015 road bikes in this year’s test, the technology is here to stay. Eighteen of the 35 road bikes we rode were equipped with discs, and several without have the option to upgrade.
We say upgrade because, no matter whether you love or hate discs, it’s difficult to argue that their performance is anything but superior to rim brakes. The power and modulation is greater and the amount of pull it takes to create the same stopping power is significantly less. The combination of those two factors makes it easier to brake later before a turn, thus maintaining additional speed in a race. Add in how well they perform in wet conditions, when rim brakes on carbon can be disastrously bad, and there are few good arguments against the tech. Every single rider who tried discs, especially on the sinuous descent off of Gates Pass and on the rainy afternoon in East Saguaro, came away convinced of their superiority.
That's not to say discs don't have a few downsides relative to rim brakes, including a slight weight penalty, aerodynamic drag, and added complication. But given that this is only the second year that hydraulic road disc brakes have been on the market, we’re confident that it’s only a matter of time before those drawbacks are eliminated.
Manufacturers seem to feel the same way, as many, including Giant, Trek, and Specialized, have begun building dedicated, top-end bikes around discs. It's costly to open disc-specific carbon molds, so the fact that companies are doing it means they believe in the technology’s long-term viability.
Vying with the Specialized S-Works Tarmac Disc for the title of most pimped-out disc roadie in the test was the Giant Defy Advanced SL 0. At $10,300, this is about as nice a bike as money can buy, and the ride quality and finishes bear that out. It’s an absolute stunner in terms of looks, and the parts pick, including Zipp 202 wheels and a Shimano Dura-Ace Di2 drivetrain, live up to the graphic design.
It’s the frame design, however, that sets the bike apart. Part of the endurance road line, the short rear triangle with thin, flattened-out seat stays and continuous seat mast with clamp-on post adds an incredible amount of vertical compliance, which makes for one of the cushiest race bikes we’ve tried. Yet the huge amount of carbon in the head tube and bottom bracket area ensures both are exceedingly stiff, making for razor sharp steering and complete power transfer from the pedals, respectively.
All told, the bike tips the scales at 15.9 pounds (size 56), which is light, though not excessively so for a bike that costs this much. That’s partly the downfall of the discs, though the comfort-oriented Aliante Fi’zi:k saddle adds some heft. And while you could pare the weight on the Defy SL 0 a bit, the fact is a half pound only really matters if you’re racing, and you won’t be racing this bike because discs haven’t yet been cleared for use by the UCI.
We had hoped to ride the much more reasonably priced Defy SL 1, which at $4,950 costs less than half the price of the SL 0. Sadly, Giant only had the top spec available for us to try in Arizona. But for our money, we’d say the SL 1 is the smart guy’s pick. It will be a bit heavier and won’t have quite the same road feel without those Zipp wheels. But since the frame is identical and the Ultegra parts are still excellent, it is sure to still be sublime.