As we entered the third week of the Tour de France, we have already had a lot of time to take a look at the riders’ bikes and there has been a lot of technical discussion during this year’s race. There have been discussions about tyres, because the debate between tubular and tubeless has been usurped through clinchers. The wheels also had their moment in the spotlight, as Jumbo Visma and Ineos Grenadiers have moved away from Shimano in favor of non-sponsor selections, despite our suggestion that Shimano has nothing new to come.
Today it’s the turn of the wheel-based component, the disc brake discs. Cyclists such as Julian Alaphilippe, Marc Hirschi and Adam Yates use MOUNTAIN rotors.
The rotors they have opted for are the Shimano RT-MT900 rotors of the brand’s ATV-centric XTR range, the SM-RT900 rotors that are part of the road-centric dura-Ace organization used by pilots.
There are differences between the two sets of rotors, the notable maximum of which is that the cooling fins are smaller in length in the XTR rotors and leave significant holes between the rotor’s central locking frame and the braking surface. Ace rotors have much larger fins that make the rotors forged to the fullest. This more economical use of curtains means that XTR rotors weigh less; nine grams less for 140 mm rotors, 10 grams for 160 mm.
The drilled holes in the rotor braking surface are also larger, which, if not tested in this application, can result in greater grip, greater functionality in rainy weather and improved cooling properties. Third, the rotor frame, which includes the central lock adapter and arms to attach to the rotor braking surface – is built differently; Dura-Ace rotors have thinner arms that bend to wheel rotation, while XTR rotors use two-legged arms that have an almost triangular shape that are more bulky in appearance Although this is not confirmed, it is a fair assumption that the result is a buildup of stiffness and durability.
There have been many rumors and speculations as to why we will delve deeper, hoping to be able to respond.
We’ll start with a warning: we have the answers. Mechanics and crews keep those decisions close to their chests, however, we’ll dive in to see what the maximum possible reasons are.
The first and maximum apparent difference is weight. As mentioned, the difference is in the order of 19 grams for a pair of 160 mm at the front and 140 mm at the rear, the maximum combination is not unusual.
Despite the potential minor benefits of weight turnover, few Tour de France groups want to save 19 grams to succeed on the 6. 8 kg ICU limit. We know from our Journal Specialized Tarmac that a 58 cm Tarmac SL7 weighs 6. 89 kg, place it in the 54 cm frame in which Alaphilippe is riding and you are already at (or below) the ICU boundary. This suggests that while weight will be a component of the equation, the full story of why groups use rotors is unlikely.
Both rotors use ‘Ice Technologies’, which necessarily combines an aluminum layer sandwiched between two layers of steel, and ‘Freezer’, which extends this layer of aluminum into cooling fins, which are then painted with a heat-dissipating paint. , one might assume that Dura-Ace rotors are better for cooling, although slightly compensated through larger holes in the braking surface of XTR rotors. It is incredibly unlikely that Tour de France riders will drag their brakes a descent, so cooling is unlikely to have been a problem, so even if there is a difference, he is unlikely to have intervened in the decision.
With the largest holes drilled on the braking surface of XTR rotors, a slight increase in braking functionality can be expected, especially on rainy terrain. A theory composed of selecting Maciej Bodnar to use XTR rotors at the last world road championship in Yorkshire year.
This could be a focus on confident descents like Hirschi, however, in all likelihood and experience, Dura-Ace brakes already offer such superior functionality that we can’t imagine any cyclist reaching such an extreme for more.
There is probably a difference, but with the turbulent air coming out of the front wheel and the minimum thickness (about 1. 8 mm) of the rotors, any difference will be small and unlikely to influence the decision.
When Roval introduced his Fast CLX wheels, they made statements about the stability of its front wheel in crosswinds and that, by reducing panic moments when the wheel goes off, the driving force must slow down to recover. Stability. With the accumulation of rotor spaces, XTR rotors will potentially be less affected by crosswinds, and with this, they are faster . . . No?
Maybe. This would be why Adam Yates used it on the front wheel only on the Dauphine, but also, it’s probably not a complete picture, because in almost every other case, they’re used on the front and back. And a 160 mm rotor will make it much less affected by the wind than a 622 mm wheel.
The play tolerance between a rim and a rim brake pad is approximately 3 mm, while that of a disc brake disc is significantly less than approximately 0. 5 mm. Therefore, if a rotor is misaligned, broken, or bent, there is much less loose area before the brake pads start rubbing.
With the highest volume of the rotor frame and its arms, the rotor could be more powerful, more powerful, and more impact-efficient.
With the amount of driving, collision, displacement, shipping and handling, it’s simple to believe a situation in which one wheel hits, falls, crashes or someone’s motorcycle tilts in opposition to another, pushing the disc out of reality. If a team is able to use a rotor that can better cope with these impacts, motorcyclists would want fewer long-term motorcycle adjustments.
With the final factories of the COVID-19 pandemic around the world in the months before this year, and with rumors about whether and when Shimano plans to upgrade Dura-Ace, could Shimano’s stock be low?
We contacted Shimano for an Array and suggested otherwise, as Ben Hillsdon tells us: “The equipment also has Dura-Ace rotors, so they can choose freely. “
Then he reiterated the weight point: “Our team’s liaison officers tell me that some groups are still suffering to get the 6. 8kg weight limit, so they’re asking for XTR rotors. Array”.
The most likely answer is a mixture of the above, as WorldTour groups are rarely decided through their technique for the progress of the device. Weight is obviously a consideration, however, greater durability would possibly be a component of the equation and potentially advanced functionality. rainy weather will be an advantage.
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