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Specialized S-Works Tarmac Disc review

28 Sep 2018

Page 1 of 2Specialized S-Works Tarmac Disc review


Proof that disc brakes can make an already excellent bike even better

Cyclist Rating: 
Fantastic integration of disc brakes; equipped for versatile terrain; impressively light and a benchmark in handling terms
Not much, although the 'Pro' tier version offers better value

Disc brakes or no disc brakes? That is the question. For Specialized it’s a more important question than for most, because it has committed totally to the move towards disc brakes, claiming that it might eventually phase out its rim brake bikes altogether.

‘The Tarmac has always been a pure-bred race bike,’ says Specialized’s Chris Riekert. ‘But I think when we launched the original Tarmac Disc two years ago [see review on page 2], the disc bike was seen as a club enthusiast’s bike because you couldn’t race it.’

Since then, however, the rules have changed – both literally and figuratively – and the bike now seems to be gaining traction with pro cyclists.

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Zdenek Stybar and Elia Viviani, both of Quick-Step Floors, have been competing on the Tarmac Disc this year, and Specialized has the stats to back up the pro endorsement.

It claims the disc version boasts the exact same overall aerodynamics as the rim brake version, which itself is as fast as the previous generation of Specialized’s aerodynamic Venge.

The frame also comes in at an impressive weight of 800g in a size 56cm – which is within 50g of the rim brake version.

If the addition of discs costs nothing in terms of weight, stiffness or aerodynamics – while offering improved braking quality – does that make the Tarmac SL6 Disc the perfect offering?

The rim brake version was certainly a bike that made an impression. At the recent Cyclist Track Day series (where visitors got to try out top-end bikes from a large number of the big brands) it was one of the most popular bikes thanks to its smooth ride, lightning acceleration and assured handling. 

Same but different

For me, the S-Works Tarmac Disc feels strikingly similar to its rim brake counterpart. The geometry is identical (on my size 56cm, at least – some smaller sizes vary marginally) and Specialized’s tradition of engineering disc frames around short chainstays means the rear is just as compact and punchy.

With the more powerful connection of a thru-axle the rear feels even stiffer at times, without suffering in terms of comfort in the way that some overbuilt disc brake frames can.

The wheels, tyres and finishing kit are all developed by Specialized and have an almost symbiotic relationship. The tyres and wheels mix grip, stiffness and comfort perfectly, and the crankset incorportes a power meter that adds just 15g to a normal S-Works carbon crankset.

Getting the power meter working was simple – once I’d worked out to peel off the plastic battery covers. The only hurdle was that the left and right sides needed to be paired using Specialized’s custom app. Many manufacturers would do that in advance, but the app was slick enough.

Once paired, the data was accurate and in-depth, and included the desirable left-right balance reading. I swapped between reading from Garmin Vector 3 pedals and the S-Works cranks regularly, and the wattage was consistent. The watts also came easily.

Partly thanks to its impressive aerodynamics, the bike lured me up to high speeds and then held me there. On long, flat roads I’d look at my bike computer and see 40kmh, and yet it always felt quite effortless. The watts seemed to be high, but the ride was so smooth and efficient that I was able
to hurt myself without even realising it.

When not engaged in subconscious masochism, I found the Tarmac Disc a joy. It mixed a natural smoothness with a healthy rumble that assured me I was moving quickly, all while feeling thoroughly connected to the road.

It combined the feel of a finely crafted steel bike with the stiffness and responsiveness of a carbon aero racer. But much of that could be said of the rim brake version. The question remains, do discs add anything? 

Braking with tradition

I’m generally sceptical of disc brakes on road bikes. Too often the trade-off of more weight, less comfort and extra cash isn’t worth it for slightly better braking performance. With the S-Works Tarmac Disc, that doesn’t seem to be the case.

It may be expensive, but it’s not that much pricier than the rim brake version, which doesn’t include the power meter. Also, the weight is perfectly acceptable at 6.83kg. What discs add to the overall package is something that does really matter, though, because the S-Works Tarmac Disc was built to descend.

The handling is exceptional. It feels planted and assured, while the accuracy and power of braking bestows huge confidence. I found myself taking on sharp corners at speed just for fun.

With the discs, I could control my entry speed all the better, as well as knowing that if I fluffed a line I could still bring the bike safely to a stop instead of binning it in a verge.

On descents it was just as sharp as the Pinarello Dogma F10, but with far less of the stiff ride quality, and I found myself dropping riders who would previously be distancing me on every hairpin.

There is some room for improvement, though. Specialized hasn’t expanded the tyre clearance much over the rim brake version, which can also accept 30mm tyres. Also, the wheel rims are carbon and lightweight, but no lighter than the rim brake version, and I suspect they are cut from the same mould.

Then there’s the pricetag. At £3,250 just for the frame, and over £9,000 for this build, it will be out of reach for the majority of riders, and it will be a year or so before we see a more affordable ‘Pro’ level version of the bike. But I can forgive all of that.

I was asked a few times whether the Tarmac Disc is the best bike I’ve ridden. It’s a question I get asked many times, and normally I steer clear of answering – all bikes are different, and people have very different tastes.

But I can’t shake this feeling that this really is as good as it currently gets. It feels so fast, so nimble, so versatile and yet does it all with a sense of grace and smoothness.

So the answer is, yes, I think it may well be.

Verdict: The S-Works Tarmac disc proves that when carefully integrated, disc brakes can improve an already excellent bike. Specialized's flagship endurance racer is pretty much as good as it gets


Specialized S-Works Tarmac Disc
Frame Specialized S-Works Tarmac SL6 Disc 2018
Groupset Shimano Dura-Ace Di2 9170
Brakes Shimano Dura-Ace Di2 9170
Chainset Specialized S-Works Power 
Bars Specialized S-Works SL Carbon Shallow Drop
Stem Specialized S-Works SL alloy
Seatpost Specialized S-Works Fact Carbon Tarmac
Wheels Roval Rapide CLX 50 Disc, Turbon Cotton 26mm tyres
Saddle Specialized S-Works Toupe
Weight 6.83kg (56cm)

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Page 1 of 2Specialized S-Works Tarmac Disc review