Tire question

[Eunos_Cosmo]

It seems most high performance road cars (exotic stuff) have very low profile, near rubber-band like tires but race cars have a much taller sidewall, why is this the case?

My guess would be something along the lines of the tall sidewall makes the tire inherently softer which will provide more grip but deteriorate much quicker thereby not be desirable on a street car.

 

[vikiradTG2007]

I've read on another site that F1 tires have such a high profile because the high sidewall is flexing more, and flexing heats it up and puts more temperature into the tire. Plus it's probably more suited to the F1 car's weight and aero behaviour. LMP prototypes and supercars work on rather different chassis and aerodynamic philosophies.


P.S. Is your avatar from Steve McQueen's "Le Mans"?

 

[Eunos_Cosmo]

Yes it is. The sports car tend to have lower profile tires, but still nothing like street cars.

 

[bartboy9891]

Yes it is. The sports car tend to have lower profile tires, but still nothing like street cars.

The tires used on the highest performance race cars have to deal with much higher cornering forces and have much stiffer sidewalls than any road car's tires because of the materials they are made of. Another way to have stiff sidewalls is to have lower profile. For supercars/sportscars it's probably easier to design the car with larger wheels in mind rather than shell out a small fortune to develop ultra stiff tires that may have a negligible impact on performance. The reason that race car tires have small wheels and higher profile may just have to do with keeping unsprung weight to a minimum.

 

[MadCat360]

A number of reasons. I don't know them all but I can list a few based on my understanding.

Larger sidewall tires tend to be easier to manage by the driver with stiff suspension. More feel, easier to get into slip angle, less snappy, etc. If, say, an Audi R8 had racecar-stiff suspension it would be quite hard to handle.

Larger sidewalls absorb the cornering force a bit better, lessening the chance of freak debeading from curbs or dropped wheels. Generally the more sideways G the larger the sidewall, which is some of why GT cars have more street sized tires.

Tire bump absorption is a better alternative to suspension absorption.

Weight, as bartboy said. Less rotational mass is always good. How much difference it makes is anyone's guess, though.

I'm sure there's some PSI reasons, as well, but I don't know them.

And standing starts! I don't know the physics behind drag cars having such huge side walls, but I know it makes a difference going from 0-100.

Tires are super important. I bet if you asked an engineer you'd get a bunch more answers. I'll ask mine next time I see him.

 

[Eunos_Cosmo]

I know drag cars use tall sidewalls purely for the amount of flex (wrinkle in drag-speak) you can get out of them. If you watch high speed footage of dragster launches, the tire spreads out like a tank track on launch.

 

[bartboy9891]

I know drag cars use tall sidewalls purely for the amount of flex (wrinkle in drag-speak) you can get out of them. If you watch high speed footage of dragster launches, the tire spreads out like a tank track on launch.

I'll take any opportunity to post this video again, watch it in HD!

[YOUTUBE]http://www.youtube.com/watch?v=ag5--q_WEIE[/YOUTUBE]

 

[Ford Prefect]

I?m not gonna get into all the tyre technology, because I?m afraid I?d mainly be spreading a bunch of ambitious half-knowledge. But the main thing to consider with road-going sportscars/supercars/whatever as well as endurance racing cars is that their brakes need to last much longer with much less air to cool them than those on F1 cars, while still providing decent braking power. This requires them to have huge discs which in turn require them to have huge rims... Quite simple really...

And also, huge rims look much cooler...

 

[Bodypaint]

I read that the formula 1 teams have tried with low profile tires on a F1 car, but the regulations says that is forbidden, and the high profile tires are also a part of the suspension of the car.

 

[pablo_h]

Hi-po cars have massive brakes, so they need massive rims. To get that to fit into a wheel arch that isn't so huge it looks out of place, you have to go with low profile rubber.

Top Gear Australia tried out the top spec HSV with huge rims, brakes and low profile rubber. Then they fitted the lower specs smaller rims, brakes and higher profile rubber. That version went faster than the big rimmed/braked version around their track because the higher profile tyre actually performed better than the ultra low profile tyre (and probably lighter brakes and rims as they are unsprung weight and the bigger and heavier they are, the worse it is for handling too)

 

[Captain Soviet]

The rim size in F1 is limited to 13 inches, I believe, which was originally introduced as a way to control brake disc diameters. As a consequence, they can't really have low-profile tyres without having the overall diameter of the wheel be too small. In time, the design of the cars evolved to use the high-profile tyres as an essential part of the suspension, and they probably couldn't go to low-profile tyres without a complete redesign of the entire suspension.