Specialized Tarmac SL5 Comp Disc – review

Specialized’s only disc-toting Tarmac bike bares its teeth, but there are flaws

The Specialized Tarmac SL5 Comp Disc provides a fast, rewarding ride with sharp yet predictable handling but, with post-mount brakes and quick releases, the frame is beginning to show its age against the very latest disc-specific race bikes.

This £2,800 machine is based around the existing Tarmac SL5 frame, launched in 2014 when disc brakes were still an emerging technology. During last year’s launch of the very latest rim brake Tarmac SL6, we were told a disc-specific version should appear at some point in 2018, but for now if you want a rotor-equipped Tarmac from Specialized, then this is it.

And why wouldn’t you look at the Tarmac? It’s been a highly-rated race machine in recent years, impressing us at the recent SL6 launch as well as when we tested the rim brake SL4 Comp bike back in summer 2016. As a frame, and a name, it’s also got an impressive pro palmares too, with wins (in its rim brake guise) under the likes of Alberto Contador and Peter Sagan to name but two.

The Tarmac SL5 Comp Disc is currently the only disc-equipped bike in Specialized’s Tarmac range (Pic: Ashley Quinlan/Factory Media)

The frame – proven race geometry, quick releases and post mounts

At the time of writing, the Specialized Tarmac range is made up of ten bikes. Of those, four use the latest SL6 frame design, three use the previous generation SL5 chassis (in rim and disc brake guises) and three are based around the SL4 frameset. Needless to say, the price drops as you move through the Tarmac range, from the £9,000 S-Works Tarmac Ultralight to the £1,500 Tarmac SL4.

  • Specialized Tarmac SL5 Comp Disc

  • Price: £2,800
  • Weight: 8.4kg (56cm)
  • Sizes: 49, 52, 54, 56, 58, 61cm
  • Size tested: 56cm
  • Website: Specialized

When Specialized overhauled the Tarmac last year, the frame received an updated and slightly more forgiving geometry that’s said to be equally suitable for men and women. There are also aero tweaks throughout, including a new fork and dropped seatstays, as well as a more compact rear triangle and a D-shaped seatpost for added comfort.

The Tarmac SL5, on the other hand, retains the curved toptube of old. That tapers towards a flattened junction with the seatpost, which is where the thin seatstays also rise to.

As for the geometry, this is a race bike and that is reflected in the numbers. A 56cm Tarmac SL5 Disc has a 160mm tapered headtube, 565mm toptube, short 405mm chainstays and 986mm wheelbase.

While the latest disc-equipped road bikes feature thru-axles and flat-mount disc brakes, the Tarmac SL5 Comp Disc has post-mount discs and quick releases. The former aren’t as aesthetically clean as flat-mount discs but, in terms of outright performance, there’s not a great deal of difference.

The frame itself is crafted from Specialized’s mid-range carbon FACT 10r carbon fibre, which is said to hit a performance-price sweetspot between the top-spec 11r and base-level 9r layup. There’s also a threaded bottom bracket, internal cable routing and a neatly integrated seatpost clamp.

The SL5 frame is beginning to show its age, with post-mount calipers and quick releases (Pic: Ashley Quinlan/Factory Media)

The ride – rewarding and responsive

While we suspect an update to the Tarmac Disc is in the works, there’s one thing that’s for sure: this SL5 Disc frameset still has life in it yet.

The ride is impressively taut and poised, providing a direct response to pressure on the pedals, while the compact wheelbase ensures the Tarmac has a quick jump. In fact, and perhaps unsurprisingly given the geometry, in many respects it’s a doppelganger for the SL4 Comp bike I tested 18 months ago.

“Whether you’re spinning seated or dancing out of the saddle, there’s lots of rewarding feedback and the potential for explosive accelerations”

The rigid carbon layup combines with an oversized bottom bracket that’s stiff enough for pretty much anyone this side of a WorldTour cyclist, so whether you’re spinning seated or dancing out of the saddle, there’s lots of rewarding feedback and the potential for explosive accelerations. Generally speaking, my maximal efforts were well dealt with by the frame, but on occasion I was able to get some disc brake rub, most obviously at the front when sprinting out of the saddle.

Specialized Tarmac SL5 Comp Disc road bike (Pic: Ashley Quinlan/Factory Media)
Specialized Tarmac SL5 Comp Disc road bike (Pic: Ashley Quinlan/Factory Media)
Specialized Tarmac SL5 Comp Disc road bike (Pic: Ashley Quinlan/Factory Media)

The stability of the ride – something that become quickly apparent with the SL4 Comp – remains. As a result, the Tarmac is incredibly predictable while descending, with the front end handling sharply but calmly as you tip the bike into bends at speed. The short wheelbase also helps with on-the-fly adjustments to your line. The short chainstays ensure the rear end reacts immediately, drawing a confident and direct line beneath your saddle.

“The Tarmac is incredibly predictable while descending, with the front end handling sharply but calmly as you tip the bike into bends at speed”

Disc brakes also help to add a further layer of assuredness, with the post-mount Shimano RS785 hydraulic brakeset doing a sterling job of producing highly effective stopping power with great modulation.

Show it decently paved tarmac, and the ride is smooth as silk. However, once things get rougher, the frameset does begin to show some weakness with a little rawness felt through the bike and contact points. The seatpost is a simple carbon affair with no trickery going on to reduce vibrations, while the cockpit is all-alloy. Of course, you could fit wider tyres than the 24mm S-Works Turbo rubber specced as standard and the fairly wide DT Swiss R470 rims (18mm internal width) will be a good match.

The build – Shimano Ultegra and solid finishing kit

Central to the SL5 Disc build is a race-ready Shimano Ultegra R8000 drivetrain, which as we’ve already discovered in its mechanical guise is a brilliantly-performing groupset that, frankly, is all the drivetrain anyone needs. You’ll even see it sported on some pro team bikes in 2018; a testament to its quality.

You even get the R8000 semi-compact chainset (often, Specialized swaps Shimano’s chainset out for a different brand), but savings have been made in the 11-28t cassette, which comes from Shimano’s third-tier 105 groupset, while the brakeset isn’t Shimano’s R8050, because that comes only in flat-mount standard.

Instead, you get the RS785 brakes, which although very good indeed, aren’t quite as tactile, nor as light as the newest Ultegra-badged calipers we got our hands on at the back end of last summer. With the industry now settling on flat-mount and thru-axle standards, there’s also a potential cap on the bike’s future upgrade potential, too.

Shimano Ultegra R8000 provides typically flawless performance (Pic: Ashley Quinlan/Factory Media)

We’ve already mentioned the DT Swiss R470 hoops – they’re smooth rolling and efficient, if a touch weighty. Still, they’re solid mid-range performers and the S-Works Turbo tyres are suitably grippy.

As well as the own-brand carbon seatpost and alloy cockpit, you also get a Specialized Body Geometry Toupe saddle. It’s not my cup of tea, but will be a good starter for many who suffer with perineal discomfort thanks to the pressure-relieving cutaway.

All this put together leads to an overall build weight of 8.4kg, which for a bike that’ll set you back £2,800 isn’t industry-leading by any stretch, but honestly didn’t have me thinking I was riding an overweight bike at any point either – a tribute to the aggressive and enjoyable ride characteristics that mask the bulk.


Fast reactions, good behaviour and a tried-and-tested geometry ensure the Specialized Tarmac SL5 Comp Disc provides a rewarding ride. However, compliance begins to suffer on really rough roads and the frame is beginning to look outdated compared to rival disc-specific race bikes.


  • Fast, rewarding ride
  • Sharp yet predictable handling
  • Excellent Ultegra groupset


  • Ageing disc frame design
  • Compliance suffers on rough roads
  • A little weighty

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