Specialized S-Works Tarmac SL6

What. A. Bike. The redesigned S-Works Tarmac – lighter, more aero and comfortable – provides superlative performance. It's a big step forward from the previous bike, and the changes push it firmly into superbike territory. It does everything extremely well; its performance is flawless.

The Specialized Tarmac should need no lengthy introduction. It's been around since 2003 and has evolved over the years to meet the needs of the most demanding bicycle racers sponsored by the US company, and in the process has won numerous victories in the biggest races – most recently at the time of writing, the 2017 World Championships in the hands of Peter Sagan.

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The 2018 version is the sixth generation and the changes are substantial; less a refinement and more a clean sheet redesign, with a focus on reducing weight, improving comfort, frame stiffness and, for the first time since the original Tarmac, added aerodynamics. It's initially available with rim brakes with the disc brake Tarmac coming next year, and is priced from £3,500 to £9,000. The model on test is the £8,500 S-Works Tarmac SL6.

Ride and handling

The performance of this new S-Works Tarmac is absolutely stunning. I've been riding it for the last few weeks, doing everything from big rides in the hills to flat-out fast chain gangs and even the occasional 60km office commute, and it hasn't done anything but impress every time I've been on it. So complete and rounded is its performance that I don't hesitate in saying this is one of the best race bikes currently available.

Specialized's goal in the redesign was to make the Tarmac better, and that is definitely something that has been achieved. I've tested numerous iterations of the previous SL5 and always found it to be a competent, if not stellar, performer. The changes to the Tarmac move it firmly into superbike territory; it's now up there with the very best money-no-object bikes I've reviewed for road.cc over the years.

The new Tarmac is much lighter than the previous bike, and this lovely S-Works build with Shimano Dura-Ace Di2 and Roval CLX 50 carbon wheels makes the most of the weight savings to produce a 6.35kg (13.99lb) build. Lighter would certainly be possible: an Ultralight frame sheds more weight with a 10g paint finish and shallower wheels, for £9,000.

Still, this bike is no heavyweight and it's certainly no slouch, with a scintillating performance on rolling terrain and in the hills which typifies my local testing roads. There's no lag or delay in the way it responds to your power, it zips up to speed very quickly, and on undulating roads it maintains momentum in the way you expect of an out-and-out aero bike. Yet when it's time to scale a 20 per cent climb it feels like a dedicated lightweight climbing bike. And somehow, despite that low weight, it never felt anything but planted and stable on the roads, no feeling of skittishness ever spoilt the sublime ride.

It's sharp and agile in the way it responds to your inputs through the handlebar too, with well-weighted steering that is neither too fast nor too slow and delivers big confidence for attacking corners and descents. The bike changes direction with startling accuracy. Despite the weight savings there's no shortage of stiffness, with a very reassuring feeling of stoutness from the front of the bike that ensures there's no vagueness when you're really pushing on at pace. And when you're doing your best Peter Sagan sprinting impression, the bottom bracket stiffness is more than adequate, despite the new slimmer BB design.

I always felt comfort was something the previous Tarmac was never short of, but the new bike provides a noticeable improvement in this department. The new seatpost with its top section engineered to provide flex – it visibly flexes when you press down on it too – really delivers fantastic seated comfort.

The way the front end handles coarse road surfaces is also impressive. With the 26mm wide Turbo Cotton tyres inflated to about 90psi the Tarmac is hugely compliant. There were never any nasty bangs or shocks through the handlebar even when the front wheel hit a series of potholes. Granted, it's no endurance bike – it doesn't compare to the Roubaix for example – but it's more composed than other overly stiff carbon race bikes I've ridden. There's even space for up to 30mm tyres if you want even more comfort for daily riding.

To sum up, the new Tarmac is a real joy to ride, as you'd obviously hope of such an expensive bike, but I've ridden bikes in this price range that haven't impressed in the same way.

Frame design

The headline-grabbing news with the new Tarmac is the low weight. A massive 200g has been shed from the previous version, with a claimed 733g weight for a 56cm frame. That's an impressive saving and puts the new Tarmac within a hair's breadth of the lightest race frames available from rival brands such as Trek, BMC and Canyon.

But there's more to the new Tarmac than just that impressive weight saving. The real feat of engineering has been in the aerodynamic wizardry that Specialized has injected into the new bike, thanks in huge part to Specialized having its own wind tunnel to verify its findings in computer simulations. Aerodynamics used to mean a weight penalty, but the new Tarmac is claimed to be as aero as the original Venge, a dedicated aero bike, yet it's far lighter than any dedicated aero bike.

We have no way of independently verifying Specialized's claims of course, but you can certainly see the aero influences. The fork blades are slim and the seatstays are dropped further down the seat tube, just like on the Venge. There's a D-shaped profile for the seat tube and new seatpost, and the rear brake is tucked lower down out of the airflow.

And you can notice the changes out on the road. Testing the new Tarmac on familiar roads with a power meter to provide some comparison data reveals that, without a doubt, it's a fast bike. As fast as some dedicated aero bikes in my opinion. Other bike brands might be producing frames that are lighter but few are also combining aerodynamics to this level. If you can have aero without the weight penalty then I can't see any reason why you wouldn't take it. Aero for free has to be a good thing, right?

Specialized introduced its Rider-First size-specific approach to frame design with the last Tarmac and has evolved it further with the new SL6. Where the previous bike used different sized tapered head tubes across the model sizes, the new Tarmac uses the same tapered head tube across the range, but three different forks with different profile blades and steerer tube taper to tune the stiffness for the smallest and largest frames.

I can't think of any other company that has developed three different forks for one bike model, and it shows a serious commitment by Specialized, not only financially because doing this can't be cheap, but also in pursuing optimum performance for each frame size.

There are some details that you might not expect on a mass-production bike, and my favourite is the carbon plate that serves to stiffen the rear brake without adding more than a few grams and helps to ensure the brake performance is crisp and dependable.

All cables are routed internally, inside the top tube on this Di2 bike, but there's a new down tube port that is compatible with other groupsets. The rear brake route is still through the top tube but the exit port has been repositioned to ensure a clean path to the brake calliper.

There's a new replaceable derailleur hanger with a lower profile and lighter design. The seat clamp is internal and easily accessed from the top tube with a rubber flap keeping crud out. I had no problems easily adjusting saddle height, and there was no slippage either. Tyre clearance is also massively improved, with 26mm tyres fitted as standard but with space for up to 30mm if you want to up the comfort.

Those changes are all wrapped up in a frame that is a big visual departure from the previous one. Out go the curves and in come straight tubes, a transition that is borne out of Specialized scaling back the diameter of the various tubes for the simple reason that a narrow straight tube is lightest. Specialized reckons that days of 'oversized stiff' are over because larger diameter tubes mean more surface area for a given wall thickness, which means more weight. It's a thoroughly modern looking bike, and there are a good selection of colours available if the stealth black doesn't float your boat.

Equipment highlights

The new Tarmac SL6 range starts at £3,500 with a Shimano Ultegra R8000 groupset. Compare that to an S-Works frameset that costs £3,250, and unless you really have your sights set on a special build, given the advances made to the latest Ultegra, that might actually be the pick of the range if you want to get onto the new SL6 platform.

It should be noted there's a small difference in the carbon fibre used. The Ultegra model uses FACT 10r carbon as opposed to FACT 12r of the highest spec models, so there'll be a small weight difference. Go the other way and the Tarmac Ultralight, with a 10g paint finish and CLX 32 wheels, costs £9,000, and is the lightest production version of the new SL6.

The S-Works Tarmac tested here is one peg down from that range-topper, with a dream equipment list for its £8,500 RRP. It all worked harmoniously and there are no changes I'd make: it's the perfect bike out of the box.

The latest Dura-Ace Di2 9150 groupset is a thing of utter joy, with fast and crisp gear changes and the direct-mount brakes solid and dependable in all situations. The junction box, through which you charge the Di2 battery and set up the gears, is now hidden at the end of the handlebar; it's a much more elegant solution than being strapped to the bottom of the stem.

Specialized's own S-Works carbon crankset with Praxis rings is the only deviation from the Dura-Ace theme but it provides good power transfer and slick shifting. It's certainly a looker, but a Dura-Ace crankset might be preferable for some. Gearing wise it's 52/36t paired to an 11-30t cassette, which provides all the gear choice you need whether you're racing or climbing mountains.

Specialized supplies the rest of the components. The Roval CLX 50 carbon clincher wheels are impressive and right up there with the best from Zipp and Enve, with great dry weather braking and adequate wet weather performance. Aero performance is good too and there's little buffeting in strong crosswinds.

Specialized has been pushing its own tyre range for a few years now and these 26mm wide Turbo Cottons are the best yet. They're grippy in all weathers, adequately dealing with the often adverse road conditions in the Cotswolds (lots of mud on the roads), and are both super-fast and, thanks to the 320TPI cotton casing, highly supple, contributing greatly to the smooth and composed ride. They also look fantastic with the tan sidewall, which does clean up pretty well after a mucky ride.

As for the finishing kit, all of it is branded with the Specialized logo, and that's no bad thing. The S-Works Toupe saddle is impressively comfortable and I'd happily (and did) sit on it all day. The SL Carbon handlebar has a pleasingly comfortable shallow drop and short reach. The aluminium stem is no-fuss, but at 100mm too short for my desired fit. The bar tape is worth a mention too: the S-Wrap with Sticky Gel provides a nice level of bump absorption as well as being very grippy with or without gloves.

Conclusion

You'd certainly hope that a bike costing £8,500 delivers an awesome performance, and, fortunately, the S-Works Tarmac doesn't disappoint. While it's an impressive feat of design and engineering, it's the way that it rides that is the best result of the complete redesign. Although it has all the credentials to be a superb race bike, it's right at home away from the demands of competition, with real-world everyday usability and comfort.

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It's this overall balance that really impresses. Specialized has managed to wrap up the weight drop, aero savings, comfort improvements and handling refinements into a package that gels really well. Until now road bikes have been specialists: the choice between a lightweight climbing bike or an aero road bike. The new Tarmac shakes up that convention, and offers the best of both worlds with no compromise.

The Tarmac has long been a popular race and performance road bike, and the latest SL6 is the best revision in its long history. It has arguably set the benchmark for future race bikes to be measured against.

Verdict

Flawless performance from Specialized's all-new Tarmac