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Mavic Ksyrium Pro Carbon SL review

Mavic Ksyrium Pro Carbon SL front wheel
23 Sep 2015

Mavic has spruced up its range for 2015, so we've taken a close look at the Ksyrium Pro Carbon SL.

It has always slightly perplexed me why a French company would invent a word with a silent ‘k’ to name a product it could literally have called anything. But whatever the reason, the Ksyrium name (pronounced sear-ree-umm by the way) has proved as enduring as the wheels that bear it.

Launched in 1999, the Ksyrium quickly became the benchmark for low profile, lightweight alloy hoops, and in its own way cemented the industry shift from handbuilt to factory built wheels, where everything from the bearings to the spoke nipples are designed by one company and assembled by machine. It’s a philosophy that’s still at the heart of the Ksyrium range, and shines through in the latest Pro Carbon SLs.

Kspeed and kcomfort

Strangely for a wheel series with lightweight qualities at its heart, this is the first time a carbon fibre rim has appeared in the Ksyrium line-up, although its introduction is about more than just satisfying the consumer thirst for carbon. ‘Braking is 48% better than our carbon competitors,’ says Mavic’s product manager, Maxime Brunand. ‘The tubular version of the Carbon Pro SL is just 1,190g, which makes it our lightest ever Ksyrium, but crucially we have made the rim wider for lower rolling resistance and better ride quality.’

Mavic Ksyrium Pro Carbon SL rim

The current consensus is that wider tyres roll faster than narrower tyres because the tyre’s contact patch is shorter, and that a tyre with a larger volume is more comfortable as it can be run at lower pressure. Thus, when Brunand says the Pro Carbons have gone ‘wider’ he means that the rim bed – the distance between the hook beads on the clincher – is 17mm (with the wheel presenting a 24mm-wide external profile), and the tyres that come specced as standard on both the clincher and tubular versions have gone from 23c to 25c.

According to Mavic, the maths goes like this: a 17.7% increase in tyre air volume decreases rolling resistance by 13%. Furthermore, Mavic’s testing shows that a 25c tyre on a 17mm rim bed inflated to 80psi has the same rolling resistance as a 23c tyre on a 15mm rim bed run at 100psi. However, the 80psi tyre will deform more readily over road bumps because of the lower pressure, thereby making the ride smoother, as well as offering more grip in the corners. Win-win in theory.

In practice

Technically still at the top of the Ksyrium tree is the £1,600 R-Sys SLR, which I’ve found to be superb in every area bar one: comfort. At 1,295g (without tyres) they’re incredibly light; the carbon spokes make them extremely stiff and the Exalith braking surface (anodised and textured to increase durability and friction) is possibly as good as it gets – if a tad noisy for some. However, because of their stiffness they don’t help out in the road bump stakes, meaning that as good as they are for climbing, I wouldn’t spec them on an all-day ride. The Carbon Pros, though, really seem to plug that gap in the Ksyrium range – light and forgiving. At 1,390g for the clinchers they’re not quite as light as the R-Sys SLRs, but I was hard pressed to notice the difference.

From the off they roll with considerable ease, and thanks to the wider rim bed and larger volume Mavic Yksion tyres (don’t get me started on those phonetics), they keep rolling incredibly smoothly and with seemingly little effort, and that definitely told on one long descent where I topped out at 100.8kmh.

Mavic Ksyrium Pro Carbon SL hub

On another wheelset I might have been tentative to go so fast, but the Carbon Pros inspire confidence. They behave almost like a traditional steel-spoked handbuilt wheel (the spokes here are bladed alloy), and as such they track the road surface with surety and dissipate road buzz well. Getting bounced around on a bike can make things feel faster, but the Carbon Pros remained resolutely smooth as I cracked my all-time top speed. Mercifully the braking was equally smooth and well modulated with no nasty judders, just a progressive increase in stopping power as anchors were dropped.

While I spent most of my time on the clinchers, I did take the 1,190g tubular versions for a short spin too, and they were arguably even better, feeling perceptibly lighter and, thanks to the nature of tubular tyres, more assured through corners.

I’d still err towards the R-Sys SLRs for the die-hard climbers, as even though the tubular Carbon Pros are lighter they are not as stiff (and the clinchers are not as stiff and slightly heavier). I’d still plump for the Exalith alloy braking surface too, as carbon is never as good in the rain. But for a low-profile, lightweight set of carbon wheels for all-round riding, the Carbon Pro SLs – clincher or tubular – are just the ticket. In fact, they might just have set a new benchmark all over again.

Mavic Ksyrium Pro Carbon SL Tubular Clincher
Weight 1,190g 1,390g
Rim Depth 25mm 25mm
Rim Width 24mm 24mm
Spoke Count 18 F, 24 R 18 F, 24 R
Price £1,425 £1,350

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