Tour Tech: Why are pros running MTB discs and is that a new set of Shimano wheels?

WorldTour races, especially early season or the Grand Tours can throw up lots of little tech tidbits that can either indicate the imminent launch of a new product or just be a curious experiment with increasing performance through the use of clever adaptation of existing kit.

Mountain bike rotors for the win?

It's the latter that caught our keen eyes at the Tour de France with regards to the trend of pros opting to run mountain bike disc rotors over the existing road versions that are more commonplace. Specifically, we're talking about Shimano and how teams such as Mitchelton-Scott and Deceuninck-Quick-Step are opting to run XTR mountain bike rotors over Dura-Ace.

So why are the teams running these? Currently there's no one specific answer, especially as teams and team mechanics hold their cards close to their chest when it comes to employing 'marginal gain' tactics.

What we do know for certain is the rotor favoured by these teams, the XTR RT-MT900 Ice Tech is lighter than the current Dura-Ace SM-RT900 Ice Tech rotor. In 160mm guise the XTR shaves a whole 10 grams off the Dura Ace and the smaller 140mm diameter is 11 grams lighter. Whilst this can be seen as pretty minimal, for a component that has an impact of how a bike rolls, i.e. rotational weight, this difference is certainly going to be advantageous (or at least give the perception of an advantage).

It's difficult to prove any performance gains by the swap as both rotors employ exactly the same construction. The braking surface utilises Shimano's Ice Technology and is formed of a sandwich aluminium and steel, with steel forming the outer faces for better braking performance and wear around an aluminium core for weight saving and heat dissipation. Both XTR and Dura-Ace also have Freeza radiator fins to help dissipate heat build-up further and it's here that the smaller fins of the XTR probably contribute to the lower weight.

So is this a performance enhancer we should all be trying? We're going to test out the swap to see if this really does make a difference and let you know the results.

Is Shimano about to launch a new wheelset?

It looks like Shimano is making up for lost time at the Tour and is throwing a multitude of new tech into the fray. We spotted something different under stage nine hero, Team Sunweb's Marc Hirschi alongside some of his team-mates and selected riders from fellow Shimano-sponsored team Groupama-FDJ in the shape of a new wheelset.

The new wheels were pretty easy to spot thanks to the matt carbon finish and unlike the unbranded Corima wheels as used by Jumbo-Visma riders, these are very much Shimano through and through. Thought to be a prototype wheel under testing the as yet unnamed wheel looks to be very much a rouleur of a wheelset with a rim depth looking to sit within the classic 40-50mm category of 'all-round' wheels.

The most noticeable difference between these and current Shimano models is it looks to employ a much wider and blunter rim profile; something that brings it bang up to date in relation to shaping used by brands such as Zipp and Enve. The wheels used by Hirschi et al look to be tubular but we would expect if this wheel is to see the light of day as a consumer item then clincher and tubeless versions should come next.