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Are there any rules of thumb for what air pressures to run, specifically on FF, FR, AWD layouts?

I know that the more air you put in the front tires, the better the response you'll get...

I was thinking, since FF will generally understeer, having less air than the fronts will allow the tires to roll more, allowing for better rotation through the corner.

Is this correct? Thoughts? Pros, Cons?

Please help!
 

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Basically you want to increase pressures so the sidewalls won't roll over. Put a line of chaulk around the area where the sidewall meets the contact patch. After a run, check to see how much of the chaulk has been rubbed off by the ground, chaulk coming off of the sidewall is a sign that your sidewalls are rolling over. You want the line to end right at the corner of the tire. Tire pressures also effect the handling of the car, increasing the fronts will yield more understeer while increasing the rears will get you more oversteer, this won't matter too much with pressures as you want the best grip available and you can adjust the balance of the car using other means (sway bars, adjustable struts)

There are more advanced methods with tire pressures involving camber and contact patch temperature. You use a pyrometer (a device that measures temperature of a surface) and check the inner, center, and outer parts of the tire tread. If the center of the tread is cooler than the inner and outer, you need more pressure. If the inner is the coolest, you need more negative camber. Be sure to record the settings somewhere including the temperature of the day and track surface type, as it will be handy in future events.
 

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Actually increase OR decreasing the rear pressures while keeping the fronts at the same pressure will induce oversteer/rotation of the car.

Both ways you are effectively decreasing the contact patch of the rear tires. When you go lower in the rear (relative to the fronts ie: 40f/35r) the car will oversteer in a slower manner that is easier to catch by just pressing on the gas pedal.

When you go higher in the rear (relative to the fronts ie: 40f/45r) the car will oversteer quickly almost to a point of snap oversteer.

Some people like one way others the other way.
 

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how about for an awd car?

when i had the civic i usually ran about 40psi front and 33psi rear, and it worked great for me. now that i have an awd car i dont know where to start.
for street i'm at 33F and 31R.
 

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iLLeFFeKt CiViC said:
how about for an awd car?

when i had the civic i usually ran about 40psi front and 33psi rear, and it worked great for me. now that i have an awd car i dont know where to start.
for street i'm at 33F and 31R.
Hrm if I remember right the guys I know running 2.5RS and WRXs use higher pressures in the rear to get the car to rotate better. Just experiment.
 

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CivicSiRacer said:
Hrm if I remember right the guys I know running 2.5RS and WRXs use higher pressures in the rear to get the car to rotate better. Just experiment.

will do. thanks
 

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tire pressures are a tricky question.. there's so many factors for choosing the right pressures.. car, driver, alignment, drivetrain.. what CivicSiRacer said is correct about running lower and higher pressure in the back relative to the front..

for my civic, i have -2.8 camber in the front, and -2.4 in the back. i run the rear lower than the front to keep the back rotating at a slower rate.. the short wheelbase will make the rear snap otherwise.. however, before i installed any camber components i was running -1 front/ -2 rear.. the only way to get the car to rotate was pumping the rear up to 50 psi.. on my accord with a long wheelbase, seems like running much higher in the rear is the only way to rotate the rear..

for awd's, it's pretty much the same rule as fwd.. that's how i treat it.. i went 42 psi front/38 psi rear when i ran the evo.. the suby's seem harder to rotate in general.. my friend with the 2.5 rs runs higher in the rear.. and he already has 1/8" toe out in both front and rear..
 

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wouldn't the way you treat an awd be car based on it's torque distribution between the front and rear wheels?

i've read that the evo (and the past dsm's) have a very fwd biased torque distributions...so people get better results with a fwd-like setup...if an awd car was rwd biased i wouldn't want to run higher pressures in the rear since that's where i want grip...this is all speculation though
 

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azian21485 said:
wouldn't the way you treat an awd be car based on it's torque distribution between the front and rear wheels?

i've read that the evo (and the past dsm's) have a very fwd biased torque distributions...so people get better results with a fwd-like setup...if an awd car was rwd biased i wouldn't want to run higher pressures in the rear since that's where i want grip...this is all speculation though
yup, which is why i treat it like a fwd.. tire pressures can go either way.. rwd, i haven't seen anyone run higher in the rear yet..

also, in stock trim, the 03 evo8 seemed to like lower pressure in the rear.. it could have been the course, but i didn't like the higher rear pressure.. my friend just traded in the 03 evo for the 05 evo rs.. he asked me to take it to auto-x so i'll see if the acd will make a difference.
 
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