Can the rims of a car affect the aerodynamic efficiency of a vehicle?

More specifically, is there a difference between rims that are closed, with no holes, and rims that have thin spokes, or rims that have angled spokes?

What I was thinking is if a car has rims with spokes that are like blades of a fan, can they pull out air from under the car to provide extra downforce, or the inverse, can they pull air in under the car to lower the downforce and reduce drag?

  • $\begingroup$ You need to look at what happens in cycling. The most aerodynamic wheel is one with no spokes but there is a problem with stability if there is a cross wind. So compare indoors momnium.com/world-beating-pursuit-bike with outdoors bikeradar.com/road/news/article/best-deep-aero-wheels-49390. Balanced this is having spokes contoured to channel air under a car and increase down force which will reduce aerodynamic efficiency but improve cornering stability. $\endgroup$
    – Farcher
    Dec 15, 2017 at 7:50
  • $\begingroup$ Thanks @Farcher, I wondered as well watching the Olympics why the wheels are solid :) On another note, I found an f1technical forum thread talking about this a bit here. It seems a fan pulling air out from the wheel wells would lower drag because air creating turbulence in the wheel wells would decrease, cleaning up airflow. PS I edited 3 times to fix the link and add this bit ;) $\endgroup$ Dec 15, 2017 at 16:45

2 Answers 2


This idea may contribute to increasing or decreasing downforce, depending on the profile of the blades.

You don't give a speed range, and I'm not sure how this would compare with the downforce generated by underbody fairings, but it's not allowed under FIA rules.

enter image description here

The Brabham BT46 fan car was banned (as it was too damn good), and if you like you could compare the angular velocity of the car's 4 wheels with that of the fan. I think this is a good argument for saying you might be on to something, but although it's easy to work out the wheel speed, I can't find anything on the angular velocity of the fan.

This is getting into EngineeringSE territory, but as I am an F1 fan (sorry) myself, I can't resist a picture to allow you to compare diameters.

The FIA ban might suggest that it is a potentially effective idea, but that it is also inherently dangerous as, at high speed, you don't want one corner of the car to unbalance an otherwise symmetrical distribution of downforce if the wheel blade profiles are not matched properly.

  • $\begingroup$ or if you lock one wheel $\endgroup$
    – user107153
    Dec 15, 2017 at 8:38
  • $\begingroup$ I loved the BT46, it's my favorite in F1 history! Thanks for the answer, that really helps settle the question for me, with the downforce symmetry and all. $\endgroup$ Dec 15, 2017 at 16:38
  • $\begingroup$ Hi Sam, welcome to PSE and thank you. It's a half engineeringSE, half physics problem. This is not physics related, but about a year ago I was in Portugal and a car pulled up beside me at traffic lights. His wheel rims were still going around, even when stopped. He must have had tiny electric motors driving the wheel covers, to impress his friends....or something :) $\endgroup$
    – user178231
    Dec 15, 2017 at 17:58
  • 1
    $\begingroup$ Countto10 that car I believe had what's called spinners on the rims. Once moving the spinners start to spin up from friction and whatnot, so once he pulled up to the light, the spinners were still rotating though he was stopped. I think spinners are dumb anyways \_('_')_/ $\endgroup$ Dec 15, 2017 at 18:05

I'm commenting on a slightly older post that discussed aerodynamics of bicycle wheels as an example for car wheels. Solid disc bicycle wheels always have lower drag, even in most crosswind situations. Unfortunately, on front wheels they make bicycles very likely to crash in even moderate crosswinds. This is because the forks do not put the center of the wheel in line with the center of steering force. Notice the curve or change in angle of most forks so that the steering is "quicker". I've never seen an analysis of bike wheel downforce, although I think it would be trivial because rolling drag is very small for bicycles (usually <5% of total drag for racing bikes at high speed) and when corning bikes lean, so that there would only be a trivial gain in cornering speed due to CG of riders body being off center of angle of bike. I am interested in car wheels now. Can a solid disc be used, or would it reduce brake cooling excessively? Why does no manufacturer that I can find make elliptical (think Ford symbol) spokes as you can buy on many bike wheels. Cd ~0.4 instead of ~1.1 for round or rectangular spokes. Cars also don't have the problem that bikes have with elliptical spokes - you don't have to make sure they are pointing straight ahead before every race.


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