New arrival: Specialized S-Works Tarmac Disc
Just in for testing is the Specialized new S-Works Tarmac Disc, a brand new model for 2015. The S-Works Tarmac Disc shares identical geometry with its rim-brake counterpart, and is one of the only full-on race-bikes equipped with disc brakes. We will be putting Specialized S-Works Tarmac Disc through the paces during the coming months. Look for an in-depth review in the upcoming June/July edition of Canadian Cycling Magazine.
[divider scroll_text=”Junction Box”]
The Specialized S-Works Tarmac Disc is equipped with Shimano’s Dura Ace Di2. We especially like this slick junction-box holder that is held by the stem face-plate bolts. Much tidier and more secure than the standard rubber strap.
[divider scroll_text=”Cable Ports”]
The S-Works Tarmac Disc features neat and tidy cable routing; the Di2 and hydraulic cables enter the down tube through the same port. There is no corresponding cable port on the opposite side. This frame is Di2 only, so it can’t be outfitted with a mechanical gruppo.
The hydraulic housing travels within the frame, popping out of the chainstay just before the R785 calipers. This setup makes for a very clean look.
[divider scroll_text=”Head Tube”]
The tapered head tube of each S-Works Tarmac Disc is size specific: the diameter at the top varies from 1 1/8″ for size 49 and 52 (our test sample), to 1 1/4″ for 54 and 56, and 1 3/8″ for sizes 58 and larger. This variation ensures consistent stiffness and feel across the size range.
The head tube is also heavily scalloped. According to Specialized, this shape avoids having any flat surface, which has a tendency to flex. Thus the scalloped-shape bolsters head-tube stiffness.
[divider scroll_text=”Seatstays”]
The seatstays are widely set, and feature sophisticated shaping: tapering from flat and wide to tall and thin along their length. All done in the name of ride quality.
[divider scroll_text=”Seatpost Clamp”]
The seatpost clamp is incorporated into the top tube, rather than the usual external collar atop the seat tube. With the clamp hidden, a little more of the 27.2-mm-diameter seatpost is exposed for added flex and compliance, again in the name of ride quality.
[divider scroll_text=”Chainline”]
The width of the rear disc brake requires the dropouts to sit 5 mm wider, which affects the chainline on race bikes with a short wheel base and chainstays, such as the Tarmac. A change in the chainline can cause shifting issues. Shimano recommends a minimum 415-mm-long chainstays for its disc-brake equipped bikes, which is part of the reason why rotors have shown up mostly on relaxed-geometry endurance road bikes. Specialized gets around any chainline issues by building a special hub that moves the cogset slightly in board, along with the corresponding derailleur hanger. The effect mimics the chainline of a regular 130-mm road spacing, preserving the same short chainstay length on the Tarmac disc as the rim-brake version.
[divider scroll_text=”Roval Wheels”]
The S-Works Tarmac Disc is equipped with Specialized’s own Roval Rapide CLX 40 wheels. The 40-mm-tall rim features a round spoke bed and hidden nipples. The Roval Rapide CLX 40 are wider than traditional rims, but not as fat as some of the current aero wheels.
[divider scroll_text=”S-Works”]
