Tire pressure

[2012Boss302]

How much does tire pressure affect the way a car steers?

Right now I am running 265 front/ 295 rear tires ( Pilot Super Sports ) the car has a tendency to push through corners. Right now I am comfortable with that because I am still learning.

My last HPDE event, my instructor told me to keep tire pressures at 38 psi hot. I did this with all 4 tires.

My question, is tire pressure used for a fine tuning tool? If I lowered my front tire pressure to say, 36 psi, and kept the rear at 38 psi, would that 2 lbs be enough to notice??

One last question, I'm thinking a better fix for this would be Camber Plates and just keeping the tires at 38 psi. Running more negative camber to increase the front traction. Am I on the right track, so to speak???

 

[Grant 302]

A lot of us fine tune with pressures. Been doing it for for years on the street to get the best wear too.
I'd also consider bumping up the pressure in the back instead. JMO, but I think PSS need higher than typical pressure since they have a really soft sidewall. Lowering the fronts hot to 36 might make it feel a bit more sloppy, especially if the 265s are on 9" rims. On a 9.5" or 10", it wouldn't matter as much for steering feel.

also see Rob's thread here:
https://trackmustangsonline.com/index.php?topic=11032.msg158467#msg158467

and Steve's thread here:
https://trackmustangsonline.com/index.php?topic=6120.0

 

[k98dave]

There are so many things that affect this besides tire pressures. Alignments / camber, temps, throttle application( smooth roll in or stab?) etc.
Changes to any of these should be done one at at time so you can find the effects. If you start playing with several areas at the same time its hard to decipher which change made a difference (or not).

Working hot pits its been my observation of race crews they seem to pay more attention to tire temp checked at center, inside, & outside area and to keep these readings within a few degrees of each other and adj pressure and or alignments from known starting numbers as needed.

 

[blacksheep-1]

The less amount of things to adjust, the more important tire pressure becomes.
One of the big nasties to show up on track cars is expansion from humidity in the tires. This can throw off pressures tremendously, the expensive fix is to purge the tires and then fill them with nitrogen, the lessor way is to purge them and use dehumidified air. Though Nitrogen is probably not necessary for street tires used on the track, dehumidified air is a real easy fix, and it eliminates a potential problem area.



Generally, covering up another problem by using tire pressures is a short lived fix, yes, it works for a few laps in qualifying or the start of a race, but sooner or later you will want all tires to come up to a specific pressure, if you increase the pressure to fix a problem, you will find that during the race two of the tires will be either too high or too low for the target pressure.
And yes, 2 psi is extremely noticeable, depending on your experience level, I try to bring in all 4 tires within .4 psi.of the target pressure.
Tire pressure is usually used to compensate for front to rear weight bias, or right vs left hand turns, as an example, at Barber, we use less pressure on the left, because they heat up more, and less on the rear for the same reason, so you might see

LF...18.5
RF...20
LR..17.5
RR..18

You can see from the above chart that if you use normal air, as the temp heads towards working temperature(180- 210) the rate of rise gets much larger than with dehumidified air or nitrogen.