Mavic's Cosmic Pro Carbon SL UST wheels make tubeless technology truly nothing to fear, with all the benefits attached. Sure, it's now a whopping £449 more expensive than the equivalent (old) clinchers, but they're still very capable performance all-rounders.
Pros: Fast, stable, stiff, good braking, easy-to-install tubeless system
Cons: Expensive, lack of ceramic bearings
When you look at Mavic's range, the Cosmic Pro Carbon SL wheelset has been at the top of the range in terms of a performance all-round wheelset for two and a half years now. Our own Mat Brett rated the original clincher versions 9/10 back in the summer of 2016 – high praise indeed.
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Of course, even before these wheels were tested, tubeless technology was already making its way onto the wheels of rival brands – so although we were mightily impressed with them, they were already beginning to look like they might be yesterday's wheels.
No longer. Almost immediately after the launch of the Pro Carbon SL Cs, Mavic began working on a tubeless evolution of the rim that could meet this emerging demand, and in partnership with tyre partner Hutchinson, has brought us this new UST (Universal Standard Tubeless) model.
The notable changes are a re-engineered, deeper rim bed with additional lip to create a secure tubeless seal, and specially designed Yksion Pro tyres to fit this new design, as well as meet the demands of tubeless running.
The main thing to take away from it is that it's just about as easy to remove and install as any snug-fitting clincher setup I've come across, while producing the same benefits – namely, better road transmission and less rolling resistance – as any other half-decent tubeless setup.
> How to fit a tubeless tyre
Obviously, Mavic can't magic away the potential mess that comes with using the sealant (they come supplied without it installed to save it drying out in shops, according to Mavic), but you can remove and seat the tyre with three levers no problem. I suspect those with stronger fingers than mine – spidery things, they are – could get away with two.
New tubeless tyres and specs
The tyres themselves – after all, they come as part of the deal, so are incredibly important to the overall experience as your contact patch – are a real upgrade. The new compound developed with Hutchinson is now grippier, more supple and emits less roar (rolling energy loss) than the old clincher WTS (wheel tyre system) – featuring Yksion Powerlink and Griplink tyres – while also seeming to be more resilient to cuts and nicks.
I've owned a few WTS wheelsets in the past, and have always felt the need (as opposed to desire) to upgrade to other tyres – Continental GP4000 IIs or Michelin Competition tyres being my choices – but there really is no need to think about upgrading here. They fit perfectly to the 25mm wide rim, and genuinely produce Schwalbe Pro One-worrying performance in the real world.
You still might want to swap if you're a Schwalbe devotee, of course, and I suspect that Schwalbe's headline tyre still has the slight edge in most areas. However, it's close; close enough that you'd seriously need to question the wisdom of spending the £119.99 (rrp) for a set. And, compared to the two Schwalbe Pro One sets I've tried, I've noticed much less air leakage with the UST system, to the point that I no longer felt the need to re-inflate tyres each and every morning.
> Buyer's Guide: Tubeless tyres – all your options
Under the new tyre and internal rim design, it's pretty much as you were with the Cosmic Pro Carbon SL USTs. I've mentioned the external 25mm rim width already, and the internal diameter sticks to 17mm too. Rim depth is 40mm both front and rear, with a NACA-inspired profile, and the rim still makes use of the excellent iTgMax laser brake track treatment.
You get Mavic's bladed steel spokes laced radially up front (18 of them) and 24 crossed-over at the rear, connected to an Instant Drive 360 freehub. That features sealed cartridge bearings that make a satisfyingly deep and dull noise when you stop pedalling.
They're smooth and quick to engage, although with the price having increased to £1,899 from £1,450 back when we first reviewed them, I couldn't help but hope for some form of ceramic bearings to appear – just as they did in some limited edition models last year.
Despite this £449 hike in price – ostensibly just for the tubeless design and attached tyres, plus some market variation – I'm still very impressed with the Cosmic Pro Carbon SL UST wheelset. I took them out to Annecy on my holiday to test them in the mountains as well as back here at home, and they excel in pretty much any conditions you can throw at them – including the gusty conditions we've had of late, where they stay remarkably stable.
On climbs they're stiff as you like, while the added transmission you get from the lack of a tube (plus the improved tyre compound) pays off when attacking descents and leaning into corners. Show them flatter roads and they'll slice through valley headwinds, and sail in tailwinds, just as their predecessors did.
All-in, they weigh 2,120g including those very competent tyres; Mavic claims that they weigh 1,490g without (665g and 825g apiece). Their clincher predecessors tipped the scales at 601g and 808g respectively, highlighting the penalty you take with heavier tubeless rubber plus the re-engineered rim. That said, I never felt held down by them in any scenario, although they can't quite live up to the overall standards set by the two-grand Bontrager Aeolus XXX 4 TLR wheelset.
> Tubeless wheelsets – 203 choices
Performance-wise, you can also find direct rivals in the competitively priced £1,550 Giant SLR 0 42mm wheels, as well as the impressively cheap £1,250 Fast Forward F4R FCC wheelset, although neither of these can boast the ease of the UST tubeless system, nor the excellent iTgMax brake track, which is still up there with the very best in all conditions.
Although not quite the performance-value proposition they used to be back when they were clinchers, Mavic's Cosmic Pro Carbon SL USTs are still competitive at this increased price point, while boasting arguably the easiest-to-install tubeless interface around.
Still very good high-spec all-rounders, now with an excellent tubeless system, but the value isn't what it once was
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Make and model: Mavic Cosmic Pro Carbon SL UST
Size tested: 700C, 40mm rim depth
Tell us what the wheel is for and who it's aimed at. What do the manufacturers say about it? How does that compare to your own feelings about it?
Mavic says: "The pinnacle of carbon clincher performance, the Cosmic Pro Carbon SL UST combines lightweight aero design with our all-new UST Road Tubeless technology.
"The result is an incredibly capable all-rounder with super low rolling resistance; a smoother, more comfortable ride quality; and the added security of a reduced risk of punctures. Plus, it's the most user-friendly tubeless system when it comes to installation, removal and maintenance. As a pioneer in tubeless technology with our proven UST system, Mavic gives you the confidence that comes with our history and expertise. The rim design of the Cosmic Pro Carbon SL UST features a 19mm inner width that's ideal for 25mm tires.
"The aerodynamic NACA profile reduces wind drag and improves crosswind stability. The rim is produced with layers of continuous carbon fiber to achieve a unique one-piece contour straight out of the mold. This technique, which we call iTgMax, offers superior heat management, allowing the rim to withstand temperatures up to 200° C. Our unique molding process and laser machining achieves a consistent braking track with nearly zero surface variations. This results in the shortest braking distances in both dry and wet conditions, with superior consistency.
"The hubs feature our lightweight, fast-engaging Instant Drive 360 freewheel system, laced with our patented aero spokes. And the wheel-tire system comes with Yksion Pro UST tires that provide a simple, hassle-free tubeless road setup with high rolling efficiency and maximum grip in all weather."
Tell us some more about the technical aspects of the wheel?
Mavic's stated "key benefits":
- Roll faster and smoother with a reduced risk of punctures.
With UST Road Tubeless, no tube means no friction. So you experience less rolling resistance and higher speeds. UST Road Tubeless lets you ride with lower tire pressure for a smoother ride quality and a reduced risk of punctures. Our patented UST system offers a perfect union between tire and wheel, so installation, removal and maintenance are easy.
- Accelerate, climb and sprint with less effort.
UST system (including sealant) is 40g lighter than a traditional tire and tube system. Aero-shaped rim features NACA profile for lower drag and improved crosswind stability. 25mm external width for improved rim/tire integration and superior handling in all conditions. Patented elliptical spokes further enhance aerodynamics.
- Descend with more confidence and control.
iTgMax technology carbon rim material can withstand temperatures up to 200° C. Laser process removes resin from brake track while leaving carbon intact, producing predictable braking performance in dry or wet conditions.
Rate the wheel for quality of construction:
I can't really fault them after over two months of use in all conditions and for all purposes.
Rate the wheel for performance:
They're very stable and I can't detect any flex in the wheel.
Rate the wheel for durability:
I've never heard any bad stories with the sealed hub bearings, while the rest of the wheel looks durable too.
Rate the wheel for weight
All-in, the wheelset (with tyres fitted) weighs a solid 2,120g. For the asking price, I'd hope for something edging a bit closer to 2000g, if not undercutting it.
Rate the wheel for value:
The clincher predecessor got 9/10 here, but these UST versions have had a £449 price increase. Yes, the tubeless system is very easy and the tyres much improved, but does that justify such an increase? That said,it's still on par with many comparable wheels out there.
Did the wheels stay true? Any issues with spoke tension?
No issues at all.
How easy did you find it to fit tyres?
Incredibly easy – just like a clincher system, to be honest. The easiest-fitting tubeless system I've come across to date (including experience with Schwalbe Pro One and Giant Gavia tyres).
How did the wheel extras (eg skewers and rim tape) perform?
No issues, although you need to make sure you get a good amount of tension in the rear axle – anything less and the wheel can move. Due diligence solves this.
Tell us how the wheel performed overall when used for its designed purpose
In all conditions, it's a grand performer with no weaknesses to speak of.
Tell us what you particularly liked about the wheel
Speed, stability, stiffness, braking performance, easy-to-install tubeless system.
Tell us what you particularly disliked about the wheel
Expensive, lack of ceramic bearings at this price when we've seen them before from Mavic.
How does the price compare to that of similar products in the market, including ones recently tested on road.cc?
Bontrager Aeolus XXX 4 TLR - £1,999.98; Giant SLR 0 42mm - £1,549.98; Fast Forward F4R FCC - £1,250.
The Aeolus are excellent and worth their weight; the Giants and FFWDs look like impressive deals next to the Mavic Cosmic Pro Carbon SL USTs.
Did you enjoy using the wheel? Yes
Would you consider buying the wheel? Yes
Would you recommend the wheel to a friend? Yes, but I'd also highlight the three rivals mentioned above as options, plus the Roval CLX50s too.
Use this box to explain your overall score
The updated UST Mavic Cosmic Pro Carbons are still very good performers, but it's harder to shine out as exceptional against competition in its new price category.
Age: 29 Height: 188cm Weight: 80kg
I usually ride: Canyon Ultimate CF SL 9.0 SL (2016) My best bike is:
I've been riding for: 5-10 years I ride: Most days I would class myself as: Expert
I regularly do the following types of riding: time trialling, club rides, sportives, general fitness riding
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