‘Obviously there is a heat transfer from the brakes and depending on where we are with rim, air and carcass temperature, we’ll decide how we want to distribute that heat transfer. That’s been the trick for a number of years now and everyone has been trying to make the best use of that,’ explains Jody Egginton, Technical Director at Toro Rosso. ‘Its no secret that people have been developing wheel rims to increase surface area by knurling and other features and its all part of the same challenge really; to improve the control of rim temp, air temp and carcass temp. We’re always looking to explore the best way to optimise brake temp and optimise carcass temp so any development we can do, whether it’s trim a brake drum or a trade off of bypass flow or a feature on a wheel we would take advantage of that within whats permitted. It’s a lot of work, but whilst there’s a performance benefit to be had, it’s our duty to exploit it.’

Andrew Green from Racing Point estimates that every 10degC increase in rim temperature sees approximately 1degC increase in tyre carcass temperature. ‘It also increases the pressure as well and increasing the pressure works the tyre harder, which generates heat in its own right so it works through two mechanisms,’ explains Green.

Front vs rear rim heating

However, rim heating is predominantly to help the front tyres as the rear tyres often struggle with overheating. ‘So we don’t even want to blow the hot air at the spokes because that will still heat the rim which will radiate onto the tyres,’ says Green. ‘We actually insulate the disc and caliper and after blowing the cool air through these components, we’ll exit that air inboard of the tyre and keep it away from the rim all together.’

‘Tyre management is very much a science in itself. On the fronts you typically try and transfer heat from the brakes into the wheel rim, it’s not the most efficient way of heating the tyres but it’s the only way you’ve got to try and maintain front temperature and get them closer to the rears,’ says Key. This is why on the inside diameter of the rims there are a variety of strange profiles and bulges. ‘These can work both ways. On the rears whilst you’re not trying to actively channel that cooling exit airflow from the brake disc onto the rims [as you would the fronts to heat the rims], that extra surface area you get from these various profiles act as a heat dissipator rather than a conductive device. But if you had very cold conditions, such as in winter testing you would reverse that.’