Mavic Cosmic Pro Carbon SL C and Ksyrium Pro Carbon SL C carbon clincher wheelsets – first ride review

Our first ride out on the new full carbon clincher rims from Mavic – in both aero and endurance guises

Mavic’s second generation carbon clincher wheels (imaginatively named internally ‘Carbon Clincher 2.0’) have now made the switch to a full-carbon rim – and, in the Cosmic Pro Carbon SL C and Ksyrium Pro Carbon SL C, our initial test rides suggest the French firm have produced two superb wheelsets: light, responsive, confidence-inspiring and with superb braking.

If you’ve read our full launch report, you’ll know that the new single mould construction process has raised the resin melting point under heavy braking, removing the need for the aluminium rim bed insert Mavic introduced with their first generation carbon clincher wheels.

– Mavic launch new carbon clincher wheelsets: full carbon, more aero, better braking –

This means the now full carbon rims are lighter than the first generation, and more responsive as a result of less weight being carried around the 40mm Cosmic Pro Carbon SL C and 25mm Ksyrium Pro Carbon SL C rims.

With that in mind, I was keen to get out and about on both wheels at Mavic’s press camp on the Cote d’Azur and put them through their paces. At the launch, we had the chance to ride both wheelsets, taking in the stiff climbs – including the Col de la Madone – and swooping descents along the French Riviera.

We tested both of Mavic’s new carbon clinchers on the roads around Monaco and Nice

Monaco, a time trial, and an encounter with Quintana

Starting in Nice on the Cosmics, the group took a coastal route out towards the town of Menton; a ride that was largely pancake flat. In the absence of a significant wind, the wheels were a joy to ride, the occasional gentle gust not affecting the stability wheel, regardless of the 40mm rim depth.

Dropping into the principality of Monaco, rounding the Grand Prix track, I stopped to take a few too many photos – falling behind the group and condemning myself to a full-bore time trial through one of the famous tunnels. The Cosmics returned my efforts excellently, with an impressively responsive sprint out the saddle to get me up to peak velocity, then rolling super smoothly to help me maintain the speed the power I could generate afforded.

These are fast wheels, no question – so fast, in fact that I was able to hitch a ride for a few minutes on the back of certain Nairo Quintana, who was out on a training ride in the area on the day. While I’m sure he was just merrily spinning away, the Cosmics gave me the chance to at least pretend that I have what it takes to survive in the pro peloton.

I was on the back of the group in no time, climbing out of the world’s most densely populated sovereign state with surprising ease. That weight Mavic has shed out of the rim – making for a total claimed weight of 1,450g for the Cosmic Pro Carbon SL C wheelset – seems to have done the job for the sheer responsiveness of the ride, especially on rims this deep, leaving me fresh at the top to ride on into Menton for our coffee stop.

While Mavic’s first carbon clinchers had an aluminium insert in the rim bed, the French firm has now made the switch to full carbon

Making the switch: Cosmic to Ksyrium

While separated from our bikes, the Mavic mechanics switched the wheels over to the Ksyriums – the lighter rims more suited climbing and endurance riding, and it’s here the real hard stuff began with a dig up the Col de la Madone.

The climb, infamously used by Lance Armstrong as he tested his pre-Tour fitness and condition, is a gradual profile of around eight per cent gradient, offering a relatively consistent effort 10km in length.

With the experience of the Cosmics behind me, I was expecting even better things out of the saddle thanks to the shallower rim depth and lower weight, and I wasn’t disappointed. Responsiveness felt superb in and out of the saddle, with accelerations shocking me into shifting up a gear in order to compensate for the sudden increase in speed. This, in spite of using the wheels on a bike (a Pinarello Dogma K8-S) which houses a suspension unit and rear end designed to soften the ride on cobbles.

Ahead of the Col de la Madone, we swapped from the 40mm-deep Cosmics for a set of 25mm-deep Ksyriums

Over slightly rougher roads on the second half of the climb, the carbon rim also proved absorbent enough through the front of the bike to avoid shaking the fillings out of my teeth – a pleasant surprise. In fact, the ride quality was so good in tandem with the native 25mm Mavic tyres supplied that at times I thought it on a par with Mavic’s best aluminium clinchers.

Cresting the top of the Madone gave us riders an opportunity to take on board food and then descend down the other side back towards Nice. First a twisty, technical, steeper descent to the main road, which eventually ran all the way down to the Promenade des Anglais – a much shallower yet faster descent that allows you to really push on with confidence.

Feeling the brakes

The Ksyriums benefit hugely from the new iTgMAX laser machining technique, with braking performance powerful and consistency reassuring throughout each heavy braking area. The feel of the braking through the levers inspires confidence – I felt ready to attack each bend, leaving it later and later to brake until my bravery (or talent?) let me down.

Another standout feature was the general lack of squealing from the rims. Under load from the brake pads, you get a low-pitched whirring sound as they bite into the laser-machined surface, which descends in pitch the more you slow down. It’s a very reassuring noise, certainly a positive affirmation that the brake pads are gripping the rims effectively, rather than noisily slipping across the surface.

The 1,390g weight of the Ksyriums mean they climb superbly – and they’re equally confidence-inspiring when the road heads downhill

Handling while descending felt superb, with the wheels responding calmly yet instantly to the lightest of leans. Mavic have widened the internal rim width to 17mm, while it measures 25mm at the brake track, and the French firm say those measurements are optimised for use with the 25mm tyres supplied. The wheels and Mavic Yksion tyres in tandem give the confidence to really chuck it into a bend and have faith that you’ll stick – no mean feat on an entirely new setup and on unknown roads.

Like the Cosmics, the Ksyriums, helped by the 25mm tyres, were effective at ironing out the worst of the feedback over bumps and road imperfections – a joy when what you need most if you’re a weaker descender is confidence and calmness in equal measure when the road is less-than-perfect.

We’ll be getting a set of the Cosmic Pro Carbon SL C and Ksyrium Pro Carbon SL C clinchers in to test in the coming weeks, and if my first impressions on the wheels on the Cote d’Azur is anything to go by, I’ll be keen to test their prowess on UK roads too.

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