The Specialized Tarmac Pro Disc Race Explains

Why Your Next Road Bike Should Have Disc Brakes

June 1, 2015 Sports and Outdoors By Photo by Henry Phillips
Specialized-Tarmac-Disk-Gear-Patrol-LEad-1440

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 Route to Ride
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.

Specialized-Tarmac-Disk-Gear-Patrol-Slide-3
Specialized-Tarmac-Disk-Gear-Patrol-Slide-2
Specialized-Tarmac-Disk-Gear-Patrol-Slide-4
Specialized-Tarmac-Disk-Gear-Patrol-Slide-1
Specialized-Tarmac-Disk-Gear-Patrol-Slide-5

Then there’s the benefit of disc brakes. The precision of their stopping power inspired more boldness in descents, and in city riding, which often has quick, hard braking, the brakes made me feel safer. As I swap between bikes on a daily basis (recently I’ve been rotating through an Evo and Transonic), I returned to the Tarmac for commuting and, when the GFNY came to town, the Tarmac was the clear choice. Psychology is a large part of performance, and for a long ride, I wanted the bike that gave me the most confidence, especially coming down the four-mile descent off Bear Mountain.

Another complaint that arises with disc brakes is appearance. And, before the Tarmac, I sat squarely in that camp. Part of this issue likely rests in the fact that most disc brakes appear on more endurance-focused frames, which tend to look less aggressive. On a performance bike, I found the disc brakes to take on the appearance of a technical development on an already technically advanced bike. It’s a small shift in perspective, but it makes a difference. As a rider, there’s also the perk of a clean visual of a front fork sans mounted brake (this is also achieved by bikes with integrated front brakes, like the Look 695 Aerolight, which probably offers the cleanest lines). And I quickly came to enjoy the shimmer of the steel/aluminum disc.

The Tarmac Pro Disc Race is one of the most proficient bicycles I’ve taken to the street, and it’s converted me to the disc revolution.

The bike is incredibly endearing to ride, partly due to Specialized Body Geometry Toupé Expert Gel seat, which is generous to your rear. The bike absorbs road noise extremely well and handles competently without being too quick or unstable. During climbs, the bike did good work to allow sustained endurance, saving energy with the smoothness of the ride and proficiently transferring power on the pedal stroke. It’s not the snappiest sprinter I’ve ridden, though it accelerates well, and when you truly throw it through the wringer the pliability that makes most of the riding comfortable makes the bike a touch soft.

But, that’s splitting hairs. The Tarmac Pro Disc Race is one of the most proficient bicycles I’ve taken to the street, and it’s converted me to the disc revolution. It inspires confidence, allows more aggressive descents and still offers the responsiveness expected from a frame designed for performance.

Around mile 67 of the GFNY, a small kicker of a hill, I rode alongside an older gentleman riding the same bike. Looking for some camaraderie and small talk, I asked him how he liked the disc brakes. He looked over, a bit baffled. I pointed to the brakes — asked again. In a thick European accent, before turning back to the road ahead, he said, “Is good.” Is very good, indeed.