On the lower level of the George Washington Bridge, early on the Sunday morning of May 17, five thousand cyclists straddled their bikes in anticipation of the Campagnolo Gran Fondo New York. And of those five thousand bikes, I spotted four — before, during and after the ride — that had disc brakes. Mine was one of them.
The Specialized Tarmac Pro Disc Race ($6,200) is one of the first performance road bikes (Colnago has also joined the ranks) equipped with hydraulic disc brakes. Unlike its endurance brethren, which more commonly have disc brakes, the Tarmac Pro maintains the qualities riders expect from a performance road bike — it charges up hills, is snappy in accelerating, and takes descents with vigor. That’s the result of Specialized’s engineers spending copious amounts of time designing around one of the least renowned parts of a bicycle: the chain stays.
In order for a drivetrain to work properly, there needs to be either a narrow hub width and/or an adequate chain stay length, to accommodate the movement of the chain and prevent cross-chain hangup at extreme angles (like when pedaling in the small ring and the smallest cog of the cassette, which can then cause the chain to catch the big ring or the shift pin and jam). Disc brakes, which have more width in the hub, require extra length in the chain stay — so endurance bikes, which aren’t expected to have the stiffness and agility in handling that a performance bike does, can keep longer chain stays to accommodate the extra width of a disc brake hub, allowing appropriate clearance. But performance bikes need shorter chain stays to maintain snappiness, and so Specialized, which has a 405mm chain stay (less than Shimano’s recommended 420mm length) needed to come up with a solution. That came by moving the cassette inward on the Roval hub, so it aligned more to a standard 130mm hub (although it is a 135mm hub).
The Tarmac excelled on the Gran Fondo New York, taking to the Bear Mountain climb without a sweat, and descending down the mountain with aplomb. It’s a fantastic show of the versatility of the bike: fast on the flats, stiff on climbs, quick on descents and comfortable over long distances. The Hyper Green also, conveniently, matches the GFNY’s green color scheme. Because matching matters. strava.com
This means the chain shouldn’t snag. But it also means you’re essentially committed to the Roval wheels — the cost of being at the front end of the disc brake curve. In a solid month of testing the Tarmac, I had neither fears nor problems with snagging, and the Rovals performed well. They’re smooth without being soft and offer some aero perks. I saw no downsides in drivetrain performance, and, unless you’re straight committed to a particular wheel set, the Rovals won’t disappoint.