[dhawcash]

Hi all.
I was wondering why F1 car tyres are relatively high profile ( tall sidewalls), when every super car boasts of rubber band thin tyres

The problem with high profile tyres and motorsport is that high profile tyres, while good at absorbing roadbumps are prone to flex and lead to a sluggish steering response due to delayed lateral aceleration- basically not good for fast driving.

Did try to find out the reasons for this online, but couldn't find a satisfactory explanation.

here is what i could find, but have a counter question for every fact listed:

1-'Tyre size rules'- F1 teams are restricted to upto 13 inch rim size. I say so what? low pros can be made for 13 inchers as well. and the resultant change in rolling radius can be counteracted by making the final drive ratio suitably taller. a lower profile tyre on 13 inch rim would also reduce the frontal area, improving areodynamics.

2. 'They are low profile'- F1 tyres are 30 or 35 profile. but being almost a foot wide translates into a high sidewall even with a low profile.
I say, there are may supercars which have footwide tyres, but still rubberband thin (eg:Gumpert Apollo). why are F1 tyres made like that?

3.' Brake size issues' - irrelevant i think- they are limited to 13 inch rim size, and the biggest disk they can fit in. fitting low profile tyres would actually improve braking ( reduced rolling radius will multiply the brake torque- if that is the right term)

4. 'F1 tyres are very stiff'- Yes agree to that- havn't ever seen a tyre flex on an F1 car. but wouldn't making a high profile tyre stiffer structurally require more bracings in the sidewall, resulting in higher tyre weight??

I'm really stumped. Even racecars for other extreme motorsports - take lemans 24 hrs- have low profile tyres. and even they have pitstops and run in similar environment.

There must be a logic for this. any ideas??

[GTO]

Originally Posted by dhawcash

I was wondering why F1 car tyres are relatively high profile ( tall sidewalls), when every super car boasts of rubber band thin tyres

Ever lifted an F1 wheel & tyre? I did at a local Bridgestone store and it was unbelievably light. I doubt that would be possible with a larger wheel.

I posed the same question actually to a Michelin race engineer on my Sepang track visit. He said that race cars barely have a suspension to speak of; seen Fonso bouncing off the kerb? That carbon fiber suspension would probably be broken to bits on a low-pro tyre. Apparently, the tyre is 50% of the suspension in an F1 car.

Also mentioned (as you have) that the rules haven't changed in decades, and FIA doesn't have any inclination to.

F1 cars anyways have tons of grip. The one advantage of low-pro tyres would be allowing bigger brakes. That's hardly a weakness with the current crop of machinery.

[rikhav]

Hi GTO

You are lucky to have one to one with a Michelin race engineer
I feel tyre war era was the most interesting of f1 in recent times
Bridgestone VS Michelin


The size and the profile of the tyre has not changed since ages but two majors things happening was re-introduction of slicks and lower width front tyre in recent years

[drkakkilaya]

speeds at which f1 cars goes is one of the reason why it is at the pinnacle of motorsport. At such high speeds there is tremendous amount of heat generated , i guess low pro tyres might just blow to bits within a few laps. Also on hitting the kerbs ,being a low profile absorption of impact is much less and the would be difficult to control ending in accident, not to mention a shattered suspension before that. Please correct if i'm wrong, but i feel this must be the reason.

[dhawcash]

I posed the same question actually to a Michelin race engineer on my Sepang track visit. He said that race cars barely have a suspension to speak of; seen Fonso bouncing off the kerb? That carbon fiber suspension would probably be broken to bits on a low-pro tyre. Apparently, the tyre is 50% of the suspension in an F1 car.

That does make sense. but i still have a bag full of doubts:
1. A tyre is basically an air spring, with very limited damping (read uncontrolled vibrations after hitting a bump). I'm not sure, but maybe the tyre engineers control that by controlling air pressures and using some wizardry in the tyre's structure.
And maybe i'm wrong, but Renault used the infamous mass damper ( a 9 KG tuned block of rubber in the nose cone, as well as somewhere in the back of the car) to improve grip by damping the tyre induced vibrations.

2. I'm quiet aware of the forces a tyre is capable of absorbing. During my engg. simulated a motorcycle with a solid wheel hitting a brick, and the forces were enough to shatter the front suspension to bits. But Other racing machines (which may be a lot heavier) also hit the kerbs while running much lower profile tyres ? what are we missing here?

3. I meant using low profile tyres on the same rim size (13") which would result in further weight reduction and the reduced rolling radius will reduce frontal area, reducing areodynamic drag. The Ride height can still be maintained by changing the angle of suspension arms. But this will reduce the contact patch size, resulting in reduced grip.
Talking of contact patches, just realized that a high profile radial tyre would have a longer contact patch compared to one with lower profile ( contact patch width would remain same as the tyre width, but its length would be longer with higher profile). So maybe grip is the reason behind the high profile??

[pranavt]

Lower profile tyres on the same rim would mean an overall shorter height tyre, which would basically mean that the tyres wouldn't even touch the ground lol.

One of the main reasons for a 13" rim is continuity. Changing wheel sizes will force redevelopment of hundreds of other components, pushing costs even higher. However, talks have been on to move to 15" rims. Perhaps 2014 might see bigger rims with lower profile tyres.

As of now, the tyres being used as a part of the suspension is a byproduct of higher sidewalls. If lower profile tyres were to be introduced, F1 engineers could easily work around the problem by using softer suspensions. The changeable suspension settings on F1 cars and high-end dampers include not only rebound and compression damping adjustments, but even fast and slow rebound and compression damping adjustments. So a car hitting a kerb would see the fast compression damping setting come into effect, while a slow-medium turn would see the slow compression setting come into effect. Thus, any issue of a softer suspension creating worse handling can be sorted easily.

[Newpunter]

There is talk to move on to bigger rims from 2014. Pirelli originally wanted to move to this profile from 2011 itself but teams objected saying that this would mean a big change and would take some time. I think F1 cars with those huge rims would look really ugly though.

[mb_jg]

I had the privilege of visiting the Penske Racing team back in 2004 sometime. I was curious of the same thing, & their engineers said that the suspension the F1 cars are almost non-existent. The tires, to an extent, manage to provide whatever cushioning they can.
With low pro's, the suspension (supposedly) would just break away with the high tension impacts & stress.
GTO is right on target with his explanation.

[dhawcash]

Lower profile tyres on the same rim would mean an overall shorter height tyre, which would basically mean that the tyres wouldn't even touch the ground lol.

Thats why i said the suspension arm angle would need to be changed.

As of now, the tyres being used as a part of the suspension is a byproduct of higher sidewalls. If lower profile tyres were to be introduced, F1 engineers could easily work around the problem by using softer suspensions. The changeable suspension settings on F1 cars and high-end dampers include not only rebound and compression damping adjustments, but even fast and slow rebound and compression damping adjustments. So a car hitting a kerb would see the fast compression damping setting come into effect, while a slow-medium turn would see the slow compression setting come into effect. Thus, any issue of a softer suspension creating worse handling can be sorted easily.

Thats exactly what i was thinking. wonder what made the go the 'high profile' way.