Review: Mavic Cosmic Pro Carbon SL C wheelset

Mavic launched the Cosmic Pro Carbon SL C to replace the Cosmic 40 C wheels in their range. Mavic have moved away from using an alloy extrusion wrapped in a carbon fibre shell to a full carbon construction and, in doing so, have managed to drop the overall wheelset weight from 1,550 g to 1,450 g with a claimed rim weight of 450 g per rim.

The alloy rim bed insert of the previous design was used to add structural integrity to the rim and, while adding durability and stiffness, drew heat caused by braking away from the carbon braking surface. On the Cosmic rims, a new patented laser treatment process is used to improve the performance of the rim brake track. The process increases the melting temperature of the resin for superior heat resistance, meaning that the resin should withstand a temperature of more than 200°C (a parameter well in excess of typical braking temperatures).

The Cosmic rims have a new rounded shape (based on a National Advisory Committee for Aeronautics profile). They are 40 mm deep with 17 mm internal width and 25 mm external width. Due to the wider internal diameter, Mavic recommends tyre widths from 25 mm to 32 mm.

The wheels come standard with a set of Mavic’s own Yksion Pro tyres with a GripLink model in the front and PowerLink at the rear – both measuring 25 mm in width and made with single compound 127 TPI casings. Along with the updates on the wheels, the tyres feature a new rubber compound and tread pattern which is said to drastically improve the characteristics of the tyres. I have not ridden the previous models, so can’t comment on that. The front and rear specific tyres weigh in at just over 210 g a piece. The Griplink’s sticky compound and water evacuation tread pattern is designed to improve front wheel cornering grip while the Powerlink seeks to keep rolling resistance low while offering good tyre life.

The hubs incorporate Mavic’s Instant Drive 360 freewheel which features a 40-tooth dual ratchet system that provides 9° engagement for near instant power transfer. Shimano/ Sram or Campagnolo freewheel bodies are available with the hub convertible to XD-R with an optional driver body. Mavic continue to build their hubs from aluminium. The hubs are designed around hollow axles and can be adapted to QR or Thru Axles with the use of end-caps. For those opting for the disc brake option, this will be even more important as it will future proof your purchase.

New elliptical straight-pull spokes, which were designed and tested in Mavic’s wind tunnel, promise to improve the aerodynamic performance of the wheelset. The front wheel is laced with a radial 18-spoke pattern with the rear wheel built using Mavic’s Isopulse 24-spoke pattern, for optimum power transfer. To maximise drive side dish and to provide a better spoke tension balance between the left and right flanges, the Isopulse pattern laces the spokes radially on the drive side and two-cross on the non-drive side.

Specifications

The Mavic Cosmic Pro Carbon SL C wheel system retails for R32,700.

On the Road

I fitted the Cosmic Pro Cabon SL C wheel system (wheels and tyres) to a 2016 Giant TCR Advanced 2 and, based on claimed weights, the wheel upgrade lobbed around 750 grams from the total bike weight. The gains were immediately evident when getting on the pedals. Whether slogging it out on a long climb or accelerating out of a corner, the combination of wheels and tyres pick up speed with meaning. This is helped by the fast engaging hubs that show little to no lag and (for those who like their hubs to have some bark) the freewheel makes a not too noisy “grrrrr”. Braking makes a unique sound too – something one would expect from the Tron: Legacy movie or an electric motor spinning down.

For those with reservations about the stopping power of carbon wheels, I can say fear not, as Mavic have found a solution with their patented design and surface treatment. Without being grabby the brakes always slowed the bike down as expected. As the Mavic supplied pads settle in there is some fine yellow dust, this however goes away as the pads and rim bed in.

To put the claimed braking performance to the test, I arranged a private shuttle session on Helshoogte during a hot Stellenbosch afternoon. I was dropped off at Tokara with the Giant and made my way down to the bottom with as much hard braking as possible. For those not familiar with the pass, it is possible to challenge and exceed the speed limit of 80km/h by just staying off the brakes.

I did this four times in a row. Throughout each run, the braking stayed consistent with a slight reduction in noise from the brake pads noticeable on my final run. Although this not a mega mountain descent, it gave me enough of a feel for the brakes to say that Mavic’s claims appear to hold true.

The wheels maintain speed well and the “U” shaped, mid-depth rims do well to hold a line in strong crosswinds. At speed, the Cosmic Pro Carbon SL C inspires confidence with no signs of flex. Once committed to a line, I could let go and allow the tyres do their work at just about any speed. In the wet, the tyres did a good job of dispersing water and giving good feedback to the rider, building confidence as one goes along. All the stiffness does not come at the expense of comfort, with the wider rims and tyres playing their part in taking the sting out of rough roads.

Verdict

Mavic took their time to release the Cosmic Pro Carbon SL C but they certainly nailed it. Mavic’s all carbon wheelset is predictable and reliable under braking while being competitively light, fast, and lively out on the road.