Help With Trackday Tyre Pressures.....

[Tractor]

I'm confused which is the best way of managing tyre pressures on a trackday.

On the road i set the tyre pressures when cold, to the manafacturers rec's. (eg, 30psi) I assume that as the tyre warms up it reaches it's optimum pressure (eg, 35psi??)

On track the tyres will get hotter and the pressure should increase more. So should i come in after some hot laps and bring the pressures down to 35psi??? Or do i just leave them as they were on road settings?? What do you guys do??

Also if i play with the settings, i assume increasing tyre pressure decreases grip slightly and vice versa? (to a point obviously!)

I'd appreciate any advice on this as i am at brands on thursday night.

Thanks very much!!

[tertius]

A reasonable rule of thumb is to run them hot on track at the recommended cold pressures. So in your example you will be bleeding air to keep them at 30 psi.

[wackojacko]

As above ^ and then tweak and record what you prefer.

[Tractor]

Thanks for your replies, very interesting. I did try this with my last car - a clio trophy. I think the pressures were 32 all round or so. I kept coming into the pits after a session and let the tyres down to 32 and after a cool down went out again. However for a car that is supposedly a Point-and-shoot hatch, i was suffering from pretty surprising understeer, especially exiting clearways. After the day the outside front tyre was bald on the sidewall!! The tyre must have been heavily rolling over. My conclusion was that i shouldnt have kept letting air out and i was running on too low a pressure???
it's just that i'm a bit reluctant to wreck my tyres if im setting them wrong. I now have a 350z however, so understeer should be less of an issue!!

[wackojacko]

Should adjust pressures when tyre has cooled down as you get different tyre temperature compared with driving style or as you get quicker through out the day and track temp etc etc

Measure pressure when you come in then adjust when cool.


With the tyre rolled over that much it suggest not enough PSI in the tyre, what tyre's were you running ?

[wackojacko]

With tyres I've not used before I start off with -15% off of the road recommended pressures.

[Tractor]

They were michelin pilot sport 2s. i agree, i must have been running too low. your suggestion sounds good. Ill try that. Thanks very much!

[GreigM]

With road tyres are you not supposed to increase pressure - as the sidewalls can't take the strain of track work and start to fold under (hence the understeer) - so while its not ideal as they overheat quicker, you need higher pressure to support the sidewalls - supporting the sidewall is more important than temperature management.

Different for track tyres (888s, A048s and slicks etc) as they have strong sidewalls and temperature management is the aim.

[edh]

Isn't this going to depend a lot on the car, driving style and tyre - if the outside of your front is worn you might just have been scrubbing it because you were going in too fast, or coming off the brakes before turning in?

I found usually your tyres told you when they have too much pressure - plenty of squealing & understeer.

I'd go for road tyres ~ cold road pressure when hot & track tyres maybe 4-6 psi less.