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I apologise for this being slightly off-topic for the stack, but it seemed the best stack for the job.

Aesthetically speaking, larger rims are preferred these days -I recently bought a Porsche with 18" rims and 55 profile tires and my peers immediately told me I should have bigger rims.

I grew up watching Formula 1, where big profiles have always been the norm, up until the current day:

enter image description here

This differs to LMP cars, who prefer the lower profile type:

enter image description here

I've studied other threads/sites that discuss larger/smaller profiles for road cars and not really seen a definitive answer above "larger rims look better".

Formula 1/Indy are seen as the bleeding edge of technology and efficiency. So, why have they continued with the larger profile tires? There must be some kind of reason for this choice above letting viewers see the brand of the tire at a larger distance (bigger profile = bigger writing).

  • What is the profile of the F1 tyres you show? – Solar Mike Jul 24 '17 at 10:10
  • The construction is different. F1 tyres dont have to last as long. They can use softer compounds. I assume its a tradeoff. – Sir Swears-a-lot Jul 24 '17 at 11:16
  • what is traded off against what? – Solar Mike Jul 24 '17 at 11:20
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According to Mercedes' Technical Director on this article (http://www.autosport.com/news/report.php/id/119331)

"The subject of bigger wheels has been raised many times over the last five or eight years," said Mercedes executive technical director Paddy Lowe.

"The broad consensus is that going to bigger wheels is not a good direction. From a grip point of view it's not positive.

"Like for like, such tyres will have a lower grip and the weight will go up considerably, so it's not an attractive direction performance-wise."

As a car corners its tyres deflect a little to keep in contact with the tarmac - stiffer sidewalls will mean less deflection and therefore less contact with the tarmac.

The size of the wheel rims will also increase mass at the hub - it takes more effort to spin the larger mass; also increasing the unsprung weight (https://en.wikipedia.org/wiki/Unsprung_mass)

" The amount of movement, for short bumps, is inversely proportional to the weight - a lighter wheel which readily moves in response to road bumps will have more grip and more constant grip when tracking over an imperfect road."

So it makes sense to keep the weight down and the tyre-wall height up from a performance point of view.

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So, given the following taken from the F1 regulations see link below:

Front max width is 385mm, max dia is 670mm (680mm for wet) then 385 / 670 is 0.57 ie less than a 60 profile

Rear max width is 470mm , same max dia so 470 / 670 = 0.7

A possible explanation is that the tyre has to do some of the work of the suspension in absorbing bumps as there is little movement.

Source: https://www.formula1.com/en/championship/inside-f1/rules-regs/tyres-and-wheels.html

  • I think the taller tyre walls are intended to reduce the speed in which a corner can be taken. As the more rubber you have on the wall the more flex there is when under load. F1 cars in the 1970's used to feature smaller wall tyres on the front than on the back. – mickburkejnr Jul 24 '17 at 13:39
  • The aspect ratio should be determined between the tread section width and the tire section height, not the overall diameter of the tire. – Pᴀᴜʟsᴛᴇʀ2 Jul 24 '17 at 18:13
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Big rims with low profile tires are a fashion statement, not the leading edge of technology. Look at the fuel consumption / CO2 emissions of any car that has several models, some of which have reasonable rim and tire sizes, and some of which have those absurd huge rims and practically no space left for tire at all.

I think you'll see that reasonably sized rims with reasonably sized tires offers the best energy efficiency. It uses less fuel, and hence more of the energy of that fuel goes to propel the car forwards. For example, in the area of the world where I live, Toyota Prius is offered with 15" and 17" rims. The 15" rims produce 70 g CO2 / km, the 17" rims produce 76 g CO2 / km or nearly 10% more.

Why would you want a car that consumes 10% more fuel, for no other benefit than as a fashion statement?

The LMP car you showed isn't as absurd as some of the big rims and low-profile tires I've seen on genuine road cars. But I wouldn't nevertheless choose these tires for a road car. They consume more fuel than they need to.

  • 1
    @Mauro, not quite true. Assuming total diameter is the same, smaller rims are typically lighter than larger rims. This equates to many advantages, such as fuel economy. See this article for the effects of changing rim sizes on a Golf. – Poisson Fish Jul 24 '17 at 14:12
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    Did some research, removed incorrect information, i still think its an unfair comparison with rolling resistance changing as well in terms of total contact patch (your article has a 40mm difference between the largest and smallest set of tyres). – Mauro Jul 24 '17 at 14:21
  • @Mauro, I agree, I think that was just the best they could do. You can still see a difference between the two tires of equal width, but it's not exactly a super scientific study. – Poisson Fish Jul 24 '17 at 15:36

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