Here is our review of the new Mavic Cosmic Pro Carbon SL C 40mm deep carbon clinchers which have a wider aero profile and are claimed to have much improved wet weather braking performance almost equal to that in the dry.
Newly launched this year the new Mavic Cosmic Pro Carbon SL C feature a wider ‘U’ shaped profile and improved brake track over the previous Mavic Cosmic 40C wheels. The new Pro Carbon SL C is also lighter than its predecessor too, with a claimed weight of 1450g vs the 1550g for the Cosmic 40C.
The new U-shaped NACA profile on the Mavic Cosmic Pro Carbon SL C is said to be more aerodynamic, more stable in cross winds and also wider than previous Mavic wheels too (17mm internal, 26mm externaL).
The improved braking is courtesy of Mavic’s iTgMax carbon technology. We’ve heard it all before – ‘improved braking on carbon wheels….’ However, the Cosmic Pro Carbon SL C are without doubt the best carbon wheels we’ve ridden when it comes to braking. To put the Mavic Cosmic Pro Carbon SL C to the ultimate test, I used them in Spain’s biggest Gran Fondo – Quebrantahuesos.
The event features three hors categorie climbs and I experienced terrible weather too. You can read about the event in more detail by clicking here.
While descending down Pyrenean climbs in the wet, I felt safe, with assured, consistent braking. There was none of the disconcerting squealing and brake fade I have experienced with other carbon wheels. All around me were other riders, many of whom were on other carbon wheels. I could hear lots of loud squealing coming from their rims, especially towards the bottom of the long descents.
We have also descended on these wheels during Paris Nice Gran Fondo, and although this event was dry, the technical descents required heavy braking at times. The same result of consistent, quiet, assured braking was observed. For riding carbon in the mountains, I wouldn’t want anything else. One caveat though – you have to use the yellow Mavic Swiss Stop pads.
The secret behind the excellent braking, is said to lie in the manufacturing process. The company has a patented process which uses a laser to prepare the braking surface. This burns away the surface resin leaving the carbon fibres intact and exposed. It has also developed a heat curing process to ensure that its rims can tolerate braking temperatures of up to 200ºC, which is at the extreme of potential real world conditions.
New production methods
There has been a lot invested into the Mavic Cosmic Pro Carbon SL C rims, which as well as the excellent braking have a claimed weight of just 450g. Although the overall wheel weight may appear slightly more than the likes of Zipp and Enve, this is misleading, because a large portion of that difference is in the relatively heavy skewers Mavic supplies. You could easily swap these. The key thing is the low 450g rim weight, which consequently has low inertia and is really noticeable when accelerating or ascending.
Creating a carbon clincher rim profile and its braking surfaces requires moulding to very close tolerances and Mavic has developed its own proprietary processes to achieve this without subsequent machining of the rim, as this can lead to cut carbon fibres and damage to the rim’s integrity.
Mavic has also tested the aero benefits of its new rims. It started by gathering data on the real world wind yaw angles experienced when riding, which are rarely much above 5 or 10 degrees. Wind tunnel testing showed best in class results for its 40mm rim at these lower angles. Our own drag coefficent testing suggested that there was very little difference between the Mavic Cosmic Pro Carbon SL C and other similar depth wheels from brands such as Zipp, Enve and Fast Forward.
They certainly provide an aero advantage though, with our drag coefficient testing suggesting a 9-10W saving at 40kph over a Mavic Ksyrium Elite rim. The Mavic Cosmic Pro Carbon SL C also uses new elliptical steel spokes to help reduce air resistance, while the hubs are Mavic Instant Drive 360, with 9 degree engagement.
What cannot be ignored is the price, which is very competitive against the likes of Zipp and Enve. Originally the UK rrp was £1450 and although this has now increased to £1600 a pair, the price is still much less than other premium brands. The weight is slightly higher than a pair of Zipp 303s or Enve 4.5s, but as previously mentioned, this is not in the rim, where inertia is most important.
The Mavic Cosmic Pro Carbon SL C come supplied with Mavic’s own Yksion 25mm tyres. Although these tyres roll nicely and offer good grip, the puncture protection is not great in our experience. They are certainly worth using until they wear out though and add to the overall value of the wheels.
It is also worth noting that Mavic is now offering a pre-purchase test programme called ‘Riding is Believing’ through selected dealers, allowing you to try before you buy. It is also offering a new warranty called Mavic Care Plus which offers a free third year and discounted crash replacement. Overall the Mavic Cosmic Pro Carbon SL C are excellent wheels, that come highly recommended. The 40mm depth, is ideal for all round use.
Although expensive, they are great value when compared to other premium brand carbon clinchers and being 40mm deep, ideal for all round use. Most of us are not going to buy specific wheels for climbing or sprint stages, so an all round do it all wheel is at this depth is ideal. I cannot shout about the braking on the Mavic Cosmic Pro Carbon SL C enough. Mavic has changed the game.