Mavic Cosmic S 42 Disc Wheelset Review

With the Cosmic S 42 Disc, Mavic demonstrates that a major brand can offer a versatile and efficient carbon wheelset for less than €1000. This is a great way to optimize the performance of a mid-range bike, especially since the Cosmic S wheels prove to be particularly reliable and easy to handle. A pleasant surprise on the road.

By Guillaume Judas – Photos: ©3bikes.fr

In the Mavic wheel range, product naming can sometimes confuse novices. The name Cosmic has represented the family of aerodynamic wheels with a medium or high rim depth for about thirty years. The S signifies the entry-level range (there are Cosmic SL and SLR at a higher range level), the 42 indicates the rim depth, and the Disc indicates the braking type.

The Cosmic S 42 Disc are wheels with modern carbon rims compatible with tubeless and tubed tires, whose U-shaped profile has been studied in a wind tunnel with an internal width of 21 mm (30 mm external width) for optimized mounting of 25 to 32 mm tire sizes.

Unlike the high-end SLR models which feature nipples directly screwed into the carbon, the drilling in the rim here is traditional with classic spoke heads, which requires the use of rim tape. The rims are built around 24 profiled steel spokes at the front and rear, and Mavic MR801 hubs with the ID360 freehub system. These are reliable and smooth hubs with double-sealed cartridge bearings that automatically adjust to tightening, but they are not the lightest models from the brand.

Result: the wheelset weighs 1660 g on the scale (897 g for the rear wheel and 763 g for the front wheel), including rim tape and tubeless valves. This is 200 to 250 g more (or even 300 g) than high-end carbon wheels with a similar rim depth, but it is barely noticeable on the road, as we will see later, because the extra weight is mainly concentrated on the hubs.

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Proven Technology

The crossed spokes have an identical length at the front and rear, which facilitates maintenance and eventual replacement. At the hubs, we find the same freehub body system as on models mounted on higher-end wheels. This is an advantage for compatibility and, again, for maintenance.

The freehub clicking noise is very subdued, which reinforces this impression of quality and reliability from my point of view. However, it is always possible to remove a rubber washer designed to dampen this noise in the freehub body, if you want to be noticed on descents or when crossing an urban area.

Finally, it should be noted that the wheels are handmade in Europe and come with a 3-year warranty. This is in addition to a Crash Replacement program, which offers a discount in case of an accident (-50% for the first 2 years and -40% between 3 and 5 years). These are additional arguments to counter those who might be tempted to equip themselves with lesser-known Asian brands, often with absent or deficient after-sales service.

Mounting tires, the cassette (here with a Shimano HG type body, but Campagnolo ED11, N3W, and XD-R type bodies are available as options) and Center Lock rotors poses no problem, although I specify that for practical reasons and personal preference I opted for classic tubed tires.

The spoke tension is quite high and well balanced on both sides, both front and rear. This obviously contributes to the overall stiffness of the Cosmic S, which are quite responsive on the road. Throughout this test, I experienced no problems with trueness, creaking noises, or freehub failure. The wheels handle energetic and repeated accelerations with behavior consistent with that of a Tarmac SL8. I never felt any stiffness mismatch between the frame and the wheels, and therefore no loss of efficiency during sharp accelerations with a large gear.

In terms of comfort, I first appreciated the silent operation of the wheels, regardless of the road surface. And with 28 mm tire sizes (measured almost 30 mm actual width once mounted on the rims) inflated to 5 bar, the absorption of small vibrations and high grip in corners are present.

Stiffness and Measured Wind Resistance

The Cosmic S 42 therefore demonstrate excellent stiffness, without being too harsh as soon as the road climbs. When the need to get out of the saddle arises to overcome a difficulty, they remain manageable and docile, without making the bike’s handling heavier.

Their extra weight compared to my usual wheels is mainly apparent when lifting the bike, but I haven’t climbed long or steep enough hills to feel it in terms of performance. The few walls I had to climb are mostly done with power, and in this area the Cosmic S are largely up to the task. The rims are not too heavy and do not penalize the overall performance of a high-end machine.

But their strong point lies above all in their stability, whether on the flats at high speed and in gusts of wind, or on descents where they truly inspire confidence. The 42 mm rim depth is a perfect compromise for a light rider, offering good aerodynamics while providing limited side wind resistance.

On the flats and with a favorable wind, I noticed no significant difference in performance compared to 50 and 60 mm deep wheels, at least at speeds between 40 and 45 km/h. The rims have greater inertia than low-profile rims, which helps maintain a good cruising speed.

With a headwind or three-quarter headwind, however, I often felt much less engaged than with deeper wheels. The frequent small trajectory corrections needed to fight against the wind when it pushes on deep-rimmed wheels can be tiring in the long run, which is much less the case with the Cosmic S 42.

On descents, I never felt any turbulence or wobbling, even beyond 60 km/h when exiting an area protected from the wind by vegetation. The wheels remain perfectly stable, whether gaining speed or applying heavy braking. The rim shape, tire width, and inflation pressure provide a lot of safety here.

A Reference Model

Aesthetically pleasing and benefiting from the recognized reliability and after-sales service of a brand like Mavic, the Cosmic S 42 Disc are excellent wheels for those who want to upgrade a mid-range bike equipped with basic aluminum wheels, or who are looking for a model designed to perform well everywhere and in all conditions.

They are not very light wheels, and they probably fall a bit short in the mountains or in high-level competitions compared to lighter, but also much more expensive, models.

With the Cosmic S 42 Disc, Mavic nevertheless offers a reliable, reassuring, and sufficient product for most riders. And whether in terms of enjoyment or handling, they also do not look out of place on a bike costing more than €10,000.

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