McLaren's Got Some Brand New Wheels

Efficient brake heat dissipation is the main design influence for today's F1 rims, and those of Enkei are a brilliant example. As can be seen, the rims have just 5 thick spokes in the central part while numerous smaller channels are designed on the outside. Note that the air injection valve is neatly integrated into the rim in an attempt to lower wind resistance to air passing through the rim.

The rear rims (inset) are of a more conventional design with a 90° oriented air valve for convenience and a tire air pressure sensor (absent on the front rims).



Finally, the rims also continue to feature coated dimples on the inside (as visible on the front rim photo) to enable the rim to absorb heat quicker, and thereby help the tires to stay at their optimal working temperature.

Even though it's been known for a while, thermal imagery has shown the true effects of rim coatings to manage tire temperatures. The coatings were first photographed on Mercedes AMG's Advanti wheels, featuring dimples on the inside of the rim as well (inset). Later on, Red Bull was confirmed to also use a similar treatment of their OZ Racing wheels, although in their case the inside of the wheels features grooves rather than dimples. Ferrari meanwhile are said to be coating their OZ Racing wheels as well.



The coating is a solvent based product containing polymers of silicium, mainly designed to protect all sorts of materials against surface friction. The product is typically sprayed to create a film of only a few microns to reach hardnesses of up to 9H. This is achieved mainly by letting the product fill up tiny gaps in the imperfect wheel surface, creating a very smooth result that may also help to reduce turbulence within the wheel.

Its black colour however is interesting for teams as that will help for the rim to absorb heat from the brakes into the Magnesium alloy wheel itself. As the rim itself has a very high thermal conductivity, the heat going into the metal is then spread rapidly throughout its entire body and partially transferred into the tire through the bead of the tire. As a result, it is possible for teams to keep the tires at a more constant temperature, reducing the rapid drop of temperature of the tires when running on long straights. Instead, with the rim properly warmed up, the tire wall is kept warm, preventing the tire's contact surface to cool off too quickly. The net result is more grip at turn-in as the tires haven't cooled down as much as without the treatment.

The thermal images in the inset show how this works brilliantly for Red Bull Racing. All three are shots from an onboard camera on Sebastian Vettel's car at Circuit of the Americas during Q1 at the US Grand Prix. The first is taken on approach to turn 19, after that looooong straight with speeds in excess of 200 mph, the second shows the turn-in point on turn 19, and the one below shows him at the end of the pit straight, before braking. It is evident that in all three images, the rim is relatively warm, and that by the end of the straight, the tyres are still lighting up across the entire thread's width. Similar images from Mercedes AMG show similar, but less pronounced effects, while on the Ferrari the wheel was not marked as hot by the thermal camera, indicating a lower temperature than with the other teams.