Tire to rim ratio

[tk421]

just curious about different racing series' tires and rims. sports cars tend to have larger rims with low-profile tires, but f1 has small rims with very high-profile tires. simple question i suppose, who's got my answer? thanks!

btw im not looking for "because the regs say so"

[Ciro Pabón]

I looked for a previous answer but could not find it. Can somebody help to locate it?

I remember that the consensus was that in F1, IRL and other series, downforce is high, so the best solution is use the tyre as part of the suspension.

[timbo]

I thought it is much simpler. Rims are limited to 13" so to get bigger contact patch and torque (from rear wheels) you have no choice but use high-profile tyres.
Maybe too simple to be true?

[Jersey Tom]

Reason why F1 runs 13" wheels is that they want to LIMIT the braking capacity of the cars. There are a variety of reasons for the actual tire size.

Sports cars on the other hand run large wheels for huge brakes and lots of suspension packaging room.

[tk421]

Reason why F1 runs 13" wheels is that they want to LIMIT the braking capacity of the cars. There are a variety of reasons for the actual tire size.Sports cars on the other hand run large wheels for huge brakes and lots of suspension packaging room.

good points--i hadnt thought of that, but why not have 18" rims and just keep the same small brake size? just because the rims are big doesnt mean the brakes have to be. not knockin ya, just askin!

so the best solution is use the tyre as part of the suspension.

i was thinking something along those lines, where they want a large volume of gas inside the tire for some reason. aside from why f1 does it that way, what are the tradeoffs between a very high and very low profile tire in general?

[gridwalker]

High profile tyres are more sensitive to tyre pressures and thus tyre temperatures, due to the greater volume of gas contained within them being subject to thermal expansion.

[ISLAMATRON]

more suspension travel within the tire sidewall flex so the suspension does not have to move as much.

[timbo]

more suspension travel within the tire sidewall flex so the suspension does not have to move as much.

I'd though it is a negative factor, no? Because tyre flexes almost as a spring without much damping - that's why they used mass dampers IMHO, to offset tyre vibration.

[mike]

smaller rims are simply lighter??

[timbo]

smaller rims are simply lighter??

don't think rim + tire combo will be lighter with smaller rims. Magnesium rims are damn light while higher tire needs thicker walls etc...

[RJC_pt]

There must be a reason, lmp have difrente size front/rears, bigger front rims, bigger walls rear

[Conceptual]

Tomba should contact the Bridgestone PR department, and ask for one of them to join this board, and answer all of these questions with the actual reasons.

Wasn't there a Michelin guy that used to frequent here before? I thought I read some old posts by him before...

[ISLAMATRON]

more suspension travel within the tire sidewall flex so the suspension does not have to move as much.

I'd though it is a negative factor, no? Because tyre flexes almost as a spring without much damping - that's why they used mass dampers IMHO, to offset tyre vibration.

yes and porpoising, but having more suspension travel would make them increase the ride height so they rather go with the big sidewalls.... I think

[mike]

tire flex could give more grip?
since it deforms easier the contact patch changes more readily??
i got an idea of it when they 1st introduce the hard and the soft compound (2007) they say that the soft makes the car move more, but it is still faster.

[Jersey Tom]

Tomba should contact the Bridgestone PR department, and ask for one of them to join this board, and answer all of these questions with the actual reasons.

Wasn't there a Michelin guy that used to frequent here before? I thought I read some old posts by him before...

There are at least two race tire engineers about...