Ride Quality 
Specialized has always put a premium on ride quality, even in their most aggressive bikes, and the S-Works Tarmac offers a surprisingly smooth and comfortable ride relative to its purpose as a pure racing bike. The rear seatstays allow for some vertical flex, which absorbs road chatter, and carbon bars up front help do the same, as carbon absorbs more than aluminum. But the bike’s overall stiffness, along with a significantly forward rider position, means it’s not ideal for longer rides especially on rougher roads—that said, with the decent compliance overall we’ve certainly ridden far less comfortable road race machines.

Stiffness-to-Weight/Power Transfer
This is where the Specialized S-Works Tarmac really shines. Specialized’s road bikes are always stiff and responsive where they need to be, and that’s taken to the highest degree here with their FACT 11r S-Works frame. The bottom bracket and crankset—where most of the acceleration and speed begins—are among the stiffest in the industry, allowing this bike to explode when power is applied. Precious little wattage is lost to flex—the bike can literally feel like it’s accelerating out from under you when big power is put to the pedals. And while this is not the lightest in the group, at 15 pounds the extraordinary stiffness makes the stiffness-to-weight ratio outstanding as well. The front-end stiffness also adds to the overall performance—when standing and cranking on the bars, for instance, there is very little give, and thus you can really hammer out of the saddle.

Climbing/Efficiency
As with pure speed, a standout climbing bike needs a very stiff bottom bracket for maximum power transfer, and the Specialized S-Works Tarmac has that in spades. The stiff front end and bars barely budged under extremely heavy torque when powering through a steady climb or especially when standing. For riders wanting minimal wasted power when climbing, this is the best choice. However, light weight is also critical—especially on the long steady ones that climb thousands of vertical feet over many miles—and the Tarmac comes in a full pound heavier than the pure climbers in this group, and riders will notice this in the serious mountains. Also critical for the long climbs is position and compliance, and the Tarmac is very strong here for a pure race machine, but again, some of the less aggressive geometries in the group may be preferable if that’s a major concern.

Descending/Handling
The Specialized S-Works Tarmac is an absolute joy on descents, especially once you get used to the extremely responsive front end. You simply look at a corner and the bike seems to dive into it: This may be a bit disconcerting at first, and some may not want this “twitchiness” at all. But for those who do, once you adjust, the bike will corner on rails and the bike will go as deep as you dare without budging. And the aggressive geometry means you can get your center of gravity super low over the front for extra speed stability. The 32mm carbon rims will flex slightly at sharp angles, but most riders won’t notice. Braking is also very strong relative to carbon brake tracks (just be careful when wet!). 

Components, Drivetrain, Shifting and Brakes
While multiple groups are available for The Specialized S-Works Tarmac, this one feature is what has become the industry standard: Shimano Dura Ace 11-speed. The 2016 swapped the crank for Specialized’s own S-Works cranks which cuts weight and adds stiffness (2017 will keep the DA), but otherwise it’s the entire group. While drivetrains have become a personal preference for many, our testing has consistently shown DA, and its little brother Ultegra, to be the smoothest shifting and most reliable of the majors, while also remaining easy to work on. Shifting is simply amazing—smooth, fast and quiet—and there are plenty of gears for all but the nastiest mountains or heaviest sprinting on the 11-28t cassette with 52/36T front rings. Our only complaint about DA is the considerably higher cost, which we don’t feel is worth the minor weight savings over Ultegra, unless money is simply not an object. Also there are no micro-adjusters on the system other than at the rear derailleur—inline barrel adjusters would be much appreciated.

The drivetrain is complemented by full-carbon bars, seatpost and saddle rails, and the braking track on the Roval wheels is fairly consistent and powerful relative to other carbon wheels. 

Wheelset
As mentioned above, the Specialized S-Works Tarmac is spec’d with the house-brand Roval Rapide CLX 32 carbon wheels featuring ultra-smooth Ceramic Speed bearing. These are outstanding aero wheels with a stiff but smooth ride, strong side-wind performance and excellent DT-Swiss hubs with straight-drive spokes all around. They come in at an extremely impressive sub-1300g for the set, making them some of the lightest in their class. There was some very minor flex under heavy stand-up sprinting, but we had to exaggerate the sprint motion to achieve it and most riders will never notice. And braking was strong, but there were other carbon wheels that performed better especially when wet.