Mavic Cosmic SL 40 wheelset review

The Mavic Cosmic SL 40 is the French marque’s cheapest carbon rim brake wheelset.

It was one of the wheelsets to survive its 2021 range cull, when Mavic practically halved its wheelset offering as it looked to streamline the business following a takeover.

Looking at the latest trends in road bike wheels design, it isn’t particularly progressive. But this is largely down to the bike world’s general shift in focus to development for disc-brake equipped bikes.

The Mavic Cosmic SL 40 has enough about it to make it a solid upgrade candidate for those content with their rim-brake bikes, although there are cheaper and more modern rim designs available if you look around.

Mavic Cosmic SL 40 details and specifications

The Mavic Cosmic SL 40 is intended to offer a continuing upgrade pathway for those still using rim-brake road bikes, while the lighter Cosmic SLR 40 (and its rim-brake LTD sibling) tops the brand’s bill.

As the name indicates, the carbon rim is 40mm deep, with a blunt NACA aero profile.

The rim has a hooked (as opposed to hookless) design, bringing compatibility for clincher and tubeless tyres.

Mavic says its ‘UST’ tubeless system makes tubeless tyre setup easier than conventional designs, with a rim hook shaped to make sliding a tyre on easier.

A few years ago, the brand’s Yksion UST tubeless tyre was said to be the perfect pairing to maximise the ease of the UST system, but since the 2021 range consolidation that saw the Yksion tyre line disappear completely, riders no longer have this option.

This is unlikely to affect the vast majority of riders, though, who often preferred to make their own tyre choice once the wheels were bought.

The rim has a 19mm internal width (26mm external), which the brand says makes it suitable for 25-32c tyres.

A width of 19mm is contemporary for a rim-brake wheelset, but is beginning to look long in the tooth compared to large swathes of the best carbon disc-brake wheelsets.

Of course, many rim-brake road bikes are limited by the clearance offered by the frame and the brake calipers. Officially, my third-generation Canyon Ultimate SL, which I used as my test rig, can only accommodate 28c tyres, as can its Shimano Dura-Ace R9100 calipers.

For rim brakes specifically, the FFWD Tyro Rim Brake wheelset is a notable example on sale today with a 21mm internal rim width, but it’s worth considering this may inflate your chosen tyre too wide for your bike.

In any case, support for larger-than-28c tyres is nice to have, but will be irrelevant to many, given the limitations of rim brake bike and component design, which has largely ground to a halt in recent years.

The Cosmic SL 40 uses Mavic’s iTgMax brake track technology to boost braking effectiveness and modulation in both dry and wet weather conditions.

This is essentially a laser-etched treatment, which creates a rougher texture, while the resin used around the area is said to be highly heat-resistant to help prevent brake fade or worse. Mavic says you should use its own carbon brake pads to maximise performance.

Launched in 2016, the technology was industry-leading at the time, and (thanks to the relative lack of rim brake wheelset tech development since) remains a high-standard setter today.

The rims lace to alloy hub shells via straight-pull, bladed steel spokes and alloy nipples.

Under the skin, the freehub houses Mavic’s ID360 ratchet design spinning on stainless steel bearings. For reference, this basic design can also be found in ENVE SES 4.5 and Foundation disc-brake wheelsets today.

All-in, including rim tape and tubeless valves, the Cosmic SL 40 wheelset weighs in at 1,629g.

Mavic Cosmic SL 40 performance

Despite the relative lack of space inside the rim cavity, I was able to manipulate a 28c Pirelli P Zero Race TLR tyre over the rim as easily as I had done previously when that tyre was tested on slightly wider rims with a larger internal cavity.

It popped into place using a track pump, and it sealed first time with my chosen tubeless sealant.

I’ve used Mavic’s UST system before, and it remains one of the easiest to get on with I’ve come across.

On the road, the Cosmic SL 40 wheelset offers a good level of overall speed, responsiveness and stability.

Compared to the similar-level Vision SC40 (£1,024/$1,302/€1,198) and Hunt 36 Carbon Aero Wide (£849) rim-brake wheelsets, both of which I have recent experience using, the Cosmic SL feels like a good match for overall efficiency.

Having said that, both of those wheelsets are markedly cheaper than the Cosmic SL 40. The aforementioned FFWD Tyro is also relatively cheap, at £969/$1,199/€1,099.

The Hunt wheelset is also just shy of 200g lighter, making that feel more immediate in its responses on steeper inclines, though the Mavic’s slightly deeper rim profile may be more efficient everywhere else.

I can’t describe the experience as especially rapid or exciting – but it was solidly competent, whether I was climbing or spinning on the flat.

Importantly, though, the Cosmic SL 40 is the rim-brake wheelset I’d choose to have with me for changeable weather, because the braking performance is exceptional.

The iTgMax track gave off a whirring noise as the pads made contact with the rim, and remained usefully functional when wet. I also struggled to glaze the pads, despite doing my best to overheat them on my local descents.

It’s worth noting that I’ve previously used this brake-track treatment on two predecessor wheelsets in the French Alps, and those rides still stand out in my memory as the best carbon rim-braking experience I’ve had to date.

In terms of ultimate performance, it’s certainly not on a par with a good hydraulic disc brake setup, but it’s also fair to say that no rim brake and wheel pairing is.

Meanwhile, the Cosmic SL 40 was unperturbed by crosswinds throughout testing.

Of course, 40mm-deep rims shouldn’t be that susceptible to gusts compared to deeper fare, but I was pleasantly surprised by how much I could relax when the wind picked up, especially when passing through gate gaps that have caught me off guard before.

Where the Cosmic SL 40 could be improved is in its overall ride quality. I found less-than-perfect tarmac a little jarring, even though I was using one of the best tubeless tyres.

In the past, I’ve ridden a Roval CLX 50 rim-brake wheelset that impressed me more in this area, but because that rim was 20.7mm wide internally, naturally it offered a greater platform for the tyre to inflate upon.

Given that rim-brake wheels largely stopped getting wider as disc-brake wheels took over at the vanguard of road bike wheel development, the Cosmic SL 40 is competing against many others with this ‘flaw’.

That said, the FFWD Tyro Rim Brake wheelset manages to pack in a 21mm rim width, and I can’t help but wonder if the Cosmic SL would benefit from an update to that effect.

Certainly, such a development would help Mavic stand out from a crowd almost wholly focused on the disc brake present and future.

Mavic Cosmic SL 40 bottom line

The Mavic Cosmic SL 40 is a solid carbon rim-brake wheelset – it delivers good overall performance with the minimum of fuss.

A particular highlight is the braking experience. While not a competitor for a disc-brake setup (sorry, fellow fans of the rim brake), Mavic’s solution is still about as good as it gets for progressive feel and wet-weather performance.

Its Achilles heel is there are competitor wheelsets that can match or better its overall sense of speed, while undercutting it on price and, in one notable case, also offering a more progressive design.

That said, in a world where the availability of carbon rim-brake wheelsets is dwindling, the Cosmic SL 40 remains a decent overall choice.