Specialized has launched the new Tarmac Disc SL6 and, in a move that may well set the trend for top-end road bikes, has made the bold decision of including its new S-Works power crankset on the spec sheet.
We’ve taken a look at the new power crankset in more detail in a separate story, but the £9,500 Tarmac Disc SL6 bike it's been strapped to is certainly newsworthy in its own right. With groupset giant Shimano also launching its own power meter, and Specialized now joining the game, will we start seeing more power meters on off-the-shelf bikes? Spesh UK’s David Alexander thinks so: "We believe going forward there will be more and more bikes specced with power meters as standard," he told us.
The Tarmac has long been established as Specialized’s all-round race bike, yet as we reported last summer at the launch of the rim brake version, the brand’s engineers have rethought the design of the SL6 frameset, making it lighter, more aerodynamic and more comfortable.
The new disc-specific frame and fork come in at a claimed 800g and 338g respectively in a size 56cm (versus 733g and 325g in the rim brake bike), so it’s extremely light as disc brake bikes go. The only geometry change to the disc brake frame is in the chainstays, which now measure 410mm in all sizes in order to accommodate the rear rotors, whereas the rim brake frame varies from 405mm to 410 mm depending on size.
The frame is laid up using Specialized top of the range S-Works FACT 12r carbon fibre, and compared to the outgoing Tarmac features an additional 200 pieces of carbon – up to 500 – which Specialized says adds complexity to the manufacture, but paves the way for strategic weight saving and claims of an improved ride (read: stiffness and handling). If it’s a match for the rim brake Tarmac SL6, which we’ve spent extensive time on recently, then that’s a very good thing indeed.
This won’t shock many given Specialized’s experience with aero frame development with the disc brake-only Venge ViAS, but brand’s so-called ‘Win Tunnel’ has clearly been put use once again with claims of zero aero loss against the rim brake bike despite the inclusion of disc brakes. While a disc brake caliper is bigger, a rim brake caliper creates more ‘dirty air’ in a key area of the bike for aerodynamics, according to Specialized.
A six-month development period also saw the realisation of an aero-optimised fork profile in three different sizes, the visibly dropped seatstays that feature a D-shape tube profile, and a truncated downtube designed to shield bottles from the wind. All-in, Specialized tells us that the new Tarmac Disc frameset is 45 seconds faster in the wind tunnel than the previous Tarmac, and is as fast as the first-generation Venge.
Unsurprisingly, the bike accommodates flat-mount calipers, while the frameset includes the ‘Flush Axle System’, which allows the supplied 12mm thru-axles to fit flush in the dropouts, apparently reducing drag, and can be removed using an Allen key. Each one saves 30g compared DT Swiss RWS thru-axles, although Specialized also supplies DT Swiss RWS axles with levers just in case riders want the added reassurance of a more conventional setup.
The frameset boasts clearance for 30c tyres, which is handy given how wide the supplied Roval CLX 50 hoops tend to blow tyres out (read our review here), while the complete bike comes with a full Shimano Dura-Ace Di2 groupset, including those distinctive black-finned rotors, premium S-Works finishing kit and the carbon S-Works power cranks.
If you haven’t read our dedicated story on those, they’re claimed to be the lightest (440g at 172.5mm in length) on the market, with dual-sided power measurement rated to +/- 1.5 per cent.
The Specialized Tarmac Disc SL6 is available in six sizes ranging from 49-61cm and will set you back £9,250. This is essentially an early model year 2019 bike, so while it’s only available in this flagship build for now, expect the Tarmac SL6 Disc range to widen later in the year. Framesets are also available, priced at £3,250.
Finally, this new Tarmac also replaces the old Amira female-specific race bike, with the new ‘unisex’ geometry designed with extensive data input from bike fit specialists Retul to ensure optimal fits for both genders - all that changes are the gender-specific contact points from the bars, saddle and crank length.