[Brad Cohen]

Brad Cohen  asked the Naked Scientists:
   
Hi,

I have a question that's been bugging me since high school physics class - which my teacher couldn't answer.  We were learning that friction was a function of area of contact and force upon that area (can't remember if I'm getting this right), so that a smaller area of contact had greater force per square inch, and equal friction.  This made me wonder why the wheels for Formula 1 cars were so big if friction was equal regardless of area of contact?

Is this just because if they were normal tires, the extreme torque and friction would blow them up?  Or is there a physics explanation as well.

Thanks,
Brad

What do you think?

[Chemistry4me]

Normal tyres need to flex sideways and up and down to absorb irregularities in the road?

[Don_1]

A small area of contact with the surface which would be given by narrow tyres would produce friction more than traction. Broad tyres spread the friction over a greater area thus improving the traction (grip or road holding).

The broader the tyre the greater the traction, but broad tyres increase the amount of friction during cornering, they are best suited to straight line travel. Narrow tyres give far less aditional friction during cornering, but the lack of traction, due to the smaller area of surface contact can lead to swerving. A compromise must be reached whereby traction and steering are optimised.

F1 tyres do become very hot during a race, in fact it is not until the tyres have become hot that they reach their peak performance.

[Chemistry4me]

So that is what they mean when they say "warming up the tires" []

[Don_1]

Yes. While they are cold they do not give their full potential grip.

[Chemistry4me]

The slick tyres also removes a lot of water from the track. Something like 20 liters?

[dentstudent]

per what?

[Chemistry4me]

No idea []

[dentstudent]

...and if they're slicks, then there is not very much water removal. They tend to aquaplane if there is too much lying water.

[dentstudent]

Formula one tyres

[Chemistry4me]

Haha, that just shows my knowledge of F1. I meant those wet weather tyres [:I]

[Don_1]

Real 'slicks' have not been used for the past 10 years. Instead Dry Weather tyres with circumferential grooves have been used.

Real slicks have been re-introduced for the 2009 season.

Here are the slicks on Alain Prost's 1983 Renault:

[LeeE]

Brad Cohen  asked the Naked Scientists:
   
Hi,

I have a question that's been bugging me since high school physics class - which my teacher couldn't answer.  We were learning that friction was a function of area of contact and force upon that area (can't remember if I'm getting this right), so that a smaller area of contact had greater force per square inch, and equal friction.  This made me wonder why the wheels for Formula 1 cars were so big if friction was equal regardless of area of contact?

Is this just because if they were normal tires, the extreme torque and friction would blow them up?  Or is there a physics explanation as well.

Thanks,
Brad

What do you think?

I think that what's confusing you is incorrectly applying friction to a rolling wheel.  Friction only really becomes a factor when the wheel is sliding across the surface instead of rolling across it.  In F-1 this only ever happens when something has gone wrong.