Mercedes wheel­rims


The con­tro­ver­sial Mercedes rear wheel­rims first ap­peared at the Bel­gian Grand Prix, and at the Mex­i­can GP the team asked stew­ards to in­ves­ti­gate them, re­sult­ing in them be­ing ruled le­gal. It’s al­ways dif­fi­cult to quan­tify what is a move­able or mov­ing aero­dy­namic de­vice. The ba­sic prin­ci­ple of cool­ing a brake disc by pass­ing air through the holes in the disc means that, like the wheel, which at the very least has spokes, they are a mov­ing aero­dy­namic de­vice. But they are not move­able and the ge­om­e­try is con­sis­tent when the car is sta­tion­ary. Adding holes in the wheels is just ex­ag­ger­at­ing the wheel-spoke de­sign.

Man­ag­ing the tyre tem­per­a­tures for both one lap in qual­i­fy­ing and over the full race is not easy. You want the tyres, es­pe­cially the fronts, to warm up quickly for a qual­i­fy­ing lap, and over a race dis­tance you want the rears in par­tic­u­lar not to over­heat. It is fairly easy to get the rears to come up to tem­per­a­ture by just spin­ning the wheels, but you don’t have

that op­tion with the fronts. So get­ting them up to tem­per­a­ture is all about us­ing the brake-disc tem­per­a­tures to in­flu­ence the wheel­rim tem­per­a­tures, which in­creases the tyre tem­per­a­tures. That’s the rea­son why Mercedes has con­cen­trated on only the rear wheels. Ba­si­cally, it has vented some cool air di­rectly from the brake-duct in­lets through the wheel spokes just out­side the di­am­e­ter of the wheel-re­tain­ing nut. This acts like an in­su­la­tor, re­duc­ing the heat trans­fer that the hot brake disc and axle have on the wheel mass.

With the brake discs run­ning at some­thing like an av­er­age of 650C and even higher just at the end of brak­ing at cor­ner en­try, the cool­ing air is then car­ry­ing some of that heat with it through the wheel­rim.

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