When you're testing one of these:

this is where you want to try it out:

The S-Works Tarmac SL6, our 2017 Bike of the Year is now available with disc brakes, and Barry has been checking it out in some of the best proving grounds for effective braking - the twisty roads of the French Pyrenees.

I think by now we're all pretty much convinced of the advantages of modern, lightweight, hydraulic disc brakes in the majority of conditions. They're not the default choice for everyone - particularly if you're building an ultralight climbing machine - but on most bikes, most of the time, what you're getting is smooth modulation, superb stopping power, lighter rims and awesome wet weather performance.

The main downside, for road bikes, is a slight weight penalty... However, there's a widely held belief that, for non-PROs at least, in hilly territory the increased braking confidence on descents will most likely outweigh any extra weight on the climbs.

Barry will be examining those advantages in more detail in a follow-up article, coming soon, but meanwhile, back to the SL6 Disc and some classic climbs:

photos by Barry Scott

The S-Works Tarmac SL6 Disc is an evolution, not a revolution. And in this case, that's a very good thing.

The rim-brake version is still in the Specialized range, giving you the option to choose the bike that best suits your riding, but we think the disc version is going to be the de facto choice for the majority of riders.

Pretty much everything Barry had to say about the SL6 in his (glowing) review holds true for the disc model. The spot-on geometry, the pin-sharp handling, they're unchanged. What Specialized have done is taken an "if it ain't broke" approach and simply beefed up the frame and forks where necessary to cope with the increased braking forces that come with discs.

Okay, that's maybe a little unfair - it's not simply a case of adding a few blobs of carbon fibre - of course there's a lot going on under the skin. But the important thing we took away from riding the newest SL6 is that you're not giving anything up by going for the disc option. It's maybe a tiny, tiny bit less perky in acceleration, but that may just be our mind playing tricks on us.

It rides just like the rim-brake version, which is undoubtedly a good thing. There's maybe a touch less reaction when climbing out of saddle but I could be imagining it.

But the other benefits are so obvious... and it has a Powermeter built in! I know £9250 sounds like a lot; but there is nothing you need to change on this bike.

above: "scattered showers" add a bit of drama to the photos (and the descents)

The Gods of Bike Testing were smiling on Barry, and he got to try the SL6 out on some properly greasy Pyrenean roads. These are the kind of damp, slippery conditions where the fine-grained control and wet weather reliability of discs come into their own.

below: as always in the mountains, the weather up top can be totally different to down in the valleys

Carbon cockpit (with titanium hardware). Ceramic bearings in the bottom bracket and both hubs. Thru-axles for stiffness where you need it, even under hard braking. Roval CLX50 carbon wheels with a "perfect all-rounder" 50mm deep profile. This is a seriously well equipped bike, and that's before we get to the Dura-Ace 9100-series groupset.

Di2 electronic shifting, Dura-Ace Hydraulic Disc brakes (and we'll talk more about the Power Cranks below). This is a bike that's packed with technology, but only what you need - there's no tech for tech's sake. When you're riding it does what it's supposed to... gets out of the way and lets you enjoy the ride.

One of our favourite things about the SL6 generation Tarmac is the classic ride and handling, something that's more in line with a Parlee or (whisper it) Colnago than what we'd usually expect from a "big brand" monocoque frame. The controllable power of the disc brakes, the precise shifting, the balance between sprightly handling and smooth ride quality - they all work together seamlessly so that you can concentrate on, and enjoy, the road.

below: the roads start to dry out, but there's plenty more climbing - and descents - to come

It's not (all) about the brakes...

The Tarmac SL6 Disc comes as standard with Specialized's own S-Works Power Cranks.

Power measurement has become mainstream in the past few years, whether you're training for fitness or for competition (or both). Having the necessary mechanics built into the crankset is a logical choice - you can swap wheels, even pedals, without worrying about recalibration or having to have multiple sets of meters.

We've long been fans of the S-Works Carbon cranks, and the Power version retain the stiffness whilst not adding too much extra weight (Specialized say they're actually the lightest way to get power measurement onto your bike, when looking at the total bike weight).

Naturally they work with all the usual range of ANT+/Bluetooth devices, regardless of brand, and we found them to be reliable and accurate in testing, when compared against our existing devices.

If this has piqued your interest, get in touch and we'll be happy to talk you through the options.

As always at Bespoke, your new Tarmac SL6 comes with a bike fit included - we'll even swap the contact points like-for-like at no extra cost to ensure the perfect fit.

The Testing Grounds

The Port de Bales is a proper old beast of a climb, still pretty much a track until given a fresh coat of tarmac in advance of the 2007 Tour de France and frequently snowed-in in winter.

There's still a wild feeling to these mountains, only accentuated when the mist closes in. As visibility decreases the reassurance provided by the reliable, fade-resistant Dura-Ace disc rotors is much appreciated.

The average incline may be 6.3%, but that stretches to 11% at points. But it's the atmosphere (and on a clear day, the views) that make this climb special.

A regular feature of the Tour de France since 1910, the Col de Peyresourde needs no introduction.

Yes, it's a Cat 1 climb, but it's the descents that really put the bike (not just the rider!) through its paces. This is where Chris Froome staged his epic attack on the descent, soloing to stage victory (and ultimately overall victory) on the 2016 Tour.

What better place to put a disc-equipped bike to the test?

(above: the summit marker also shows the boundary between départements of Hautes Pyrenées and Haute Garonne)