Tire Pressure vs Temperatures

[hardingfv32]

Is this statement from James Allen correct? Does the effect of tire pressure changes trend the same way for most racing tires?

"The other was getting the wrong tyre pressures; too much pressure and the tyres would warm up quickly, then suffer loss of performance, too little tyre pressure and they might never get into the optimum temperature window."

Brian

[Jersey Tom]

Is this statement from James Allen correct? Does the effect of tire pressure changes trend the same way for most racing tires?

"The other was getting the wrong tyre pressures; too much pressure and the tyres would warm up quickly, then suffer loss of performance, too little tyre pressure and they might never get into the optimum temperature window."

Brian

Yes and no. Suffice to say it's not quite that simple. Sometimes being too low on air pressure will make a tire run too hot.

[Cold Fussion]

By what mechanism does greater tyre pressure increase tyre temperature?

[PhcF1]

Tire pressure affects the pressure distribution of the footprint and consequently the tread temperature...

[marcush.]

there is a lot of it related to temps but I ´d say the temps are more an effect than a cause.

so you put on a brandnew set of tyres and go out for a qualifying attempt-would you want a single lap from them or 2 timed laps ? I ´d certainly start with a much lower pressure for a two timed laps effort than a 1 lap make it stick effort.
Then you try the same with a set of tyres already scrubbed in....presto ,more cold pressure needed as the tyres will certainly not again go through their initial cycle so the pressure rise inside the tyre will not be as severe.
But then there is that old set you went 40something laps on yesterdays and you would like to evaluate for comparison reasons todays....not much rubber left on it but .....how much less of a pressure rise those will see ?


Phenomenally most drivers instantly complain of loss of grip when pressures are climbing too much .They dive into the pits you releave the odd 0.1 or 0.2bars on the axle which is giving less grip and shows a temperature peak in the middle of the thread and presto you are already there .Anticipating the pressure rise for the car and driver combo on a particular track and tyre condition + wheather influence sometimes looked like a magic bullet but you get a handle on this pretty quickly.

the wildest of drivers were those giving me the biggest headaches with cold pressures as they quickly banged on the door of overinflation with their energy intensive style -you can delay it a bit but really those guys have to learn how to drive within the limits of the car.

I also had an expereince with tyres intended for higher downforce than our car had on offer.Those tyres gave nothing and lost nothing with increasing or decreasing pressures.We ended in destroying the tyres by underinflating them too much which overstressed the carcass and even then they barely showed any temperature in the tread...so thes were very insensitive to inflation pressure.

[thisisatest]

Then you try the same with a set of tyres already scrubbed in....presto ,more cold pressure needed as the tyres will certainly not again go through their initial cycle so the pressure rise inside the tyre will not be as severe.
But then there is that old set you went 40something laps on yesterdays and you would like to evaluate for comparison reasons todays....not much rubber left on it but .....how much less of a pressure rise those will see ?

why, exactly, would a used set of tires not increase in pressure and temperature the same? i see one possible theory, that the rubber has been heat cycled and will not have the grip, so there will be less energy being applied. is that correct? otherwise, with less rubber on the tire, i would think the carcass would warm up more quickly.

[Jersey Tom]

why, exactly, would a used set of tires not increase in pressure and temperature the same?

Amount of core temperature generated has proportionality with how much rubber there is on the tread. Less rubber = less heat.

[marcush.]

is there a loss in mass when scrubbing in tyres? i have to admit I only came across this question after quitting racing ,so i have no data available and have never heard of anyone weighing tyres before and afte each run.
The loss in rubber mass is a factor in heat generation but the initial "thermosetting" or baking or whatever you call it will have a distinct effect on pressure rise.
I have mentioned it before in other threads,the thermal cycling of the tyre as a preparation detail is not to be underestimated.If you´d decide to cook your tyres at 150°C overnight I´m pretty sure your driver will not recognize the tyreset he qualified on only 24hours before...

[Jersey Tom]

Sure, bound to lose some any time you go out. More on some cars / series than others. But certainly, tread properties will start to change with any amount of heat history.

[marcush.]

Sure, bound to lose some any time you go out. More on some cars / series than others. But certainly, tread properties will start to change with any amount of heat history.

So it does make sense to actually log energy put through each tyre and maybe even log the cycles -not only macrostep count (1 session ,1 turn ...) but also :100 maximum decel ,100 times full aceleration ,5 times cornering at 3gs etc ...would be very interesting to actually see if my full bucket of water theory is actually worth something .

my idea is treating the tyre gentle at the start of a stint avoiding overstressing as much as possible will give a lot more life and a better average time and a longer stint than cooking the tyres at the beginning and nursing them when you feel them giving up on you ...

[Jersey Tom]

Sure, bound to lose some any time you go out. More on some cars / series than others. But certainly, tread properties will start to change with any amount of heat history.

So it does make sense to actually log energy put through each tyre and maybe even log the cycles -not only macrostep count (1 session ,1 turn ...) but also :100 maximum decel ,100 times full aceleration ,5 times cornering at 3gs etc ...would be very interesting to actually see if my full bucket of water theory is actually worth something .

my idea is treating the tyre gentle at the start of a stint avoiding overstressing as much as possible will give a lot more life and a better average time and a longer stint than cooking the tyres at the beginning and nursing them when you feel them giving up on you ...

I think you'd have a hard time deciphering much of value from it, with any level of confidence.