change in contact patch area with speed?

[bazanaius]

Hey everyone, after reading the tyre growth thread, and seeing the photo of the bmw F1.08 here viewtopic.php?f=6&t=5425&view=unread#unread

it strikes me that the contact patch of the tyre would be significantly smaller when the car is at low speed, as the extra downforce created at high speed would compress the tyre, no?

I guess factors affecting this are tyre pressures, tyre compound and build, downforce setup, car weight, balance, camber, maybe toe?..

Do the teams design for this? i.e. is it a significant enough effect to to be considered? Presumably it would affect braking, acceleration, wheel spin, tyre wear etc.

just wondering if people had thought about this much previously?

Baz

[Jersey Tom]

Correct.. as the car develops aerodynamic download, that force is reacted to the tires. Makes the contact patch larger, allows the tires to develop more grip, etc.

You lose downforce when you go slow. Its just something you live with and make the best of.

[bazanaius]

Thinking about this its more obvious than I make out I'd just always thought of downforce as increasing the reaction of the car with the ground, whereas this also makes it apparent that the level of grip increases due to the contact patch changing as well. I know designers take great care in suspension designs to maximise the use of the contact patch (hence things like the J-dampers) - I guss this just makes their job more complex
B

[John Stitch]

Hi,

First post.

I just thought I would add that centrifugal force would tend to make the tyre increase in diameter as the wheel spins faster so this would, to some extent, counteract the effect of the downforce on the contact patch.

By how much?

Sorry, don't know.

[The FOZ]

Hi,

First post.

I just thought I would add that centrifugal force would tend to make the tyre increase in diameter as the wheel spins faster so this would, to some extent, counteract the effect of the downforce on the contact patch.

By how much?

Sorry, don't know.

Agree. The center of the tire will want to stretch outwards, resulting in a no-flat contact patch.

And I don't think the added downforce would be compressing the tire so much as moving the suspension through it's travel. But I guess the forces would be passed through the suspension to the tires, so I don't know...

[Ciro Pabón]

All forces has to pass throught the contact patch "in the end". Suspension travel only diminishes peak forces.