2011 SCCA Runoffs

[Jason@SportsCar]

Originally Posted by racerb

. My Celica is just a bit heavier, but with Kumho V700s on it, I was running 34-36 psi up front and between 30-32 in the rear. On my old Nissan Pulsar which only weighed about 1900 lbs. and was also front drive, I would run about the same front pressures but only 18-20 psi rear.


racerb

I know some people like to drop the rear pressure to get rotation... But that is not the direction I would go. It makes for unpredictable handling, as the sidewalls wallow, and it kills the outside edge of the tire. If you want to free up the back of the car raise the pressure - it makes the breakaway much more predictable, preserves the edge of the tire, and effectively increases rear spring rate which helps keep weight on the front tires.

In the B-Spec Yaris we are running 36psi cold (Goodyear Eagle RS DOT R race tires) all the way around, we want a hot pressure around 42psi in the front. Alignment is -2.5 camber in the front, with a 1/16" toe out, and the factory alignment in the rear (I think it is about -1 with about 1/8" toe in). The car is very easy to drive this way.

On our Spec-V that weighs 3100lbs and has no camber adjustment, we end up 40psi cold front, and 60psi rear to get the balance we want. We might have gone higher in the rear, but our gauge maxed out at 60psi.

Rice, keep in mind that in Solo you are typically setting to a hot pressure, and bleeding down between runs, on the track you want to hit that same hot pressure, so you have to start lower to allow for tire/temp growth.

[ilikerice]

Originally Posted by Jason@SportsCar

Rice, keep in mind that in Solo you are typically setting to a hot pressure, and bleeding down between runs, on the track you want to hit that same hot pressure, so you have to start lower to allow for tire/temp growth.

hmm.. interesting, I didnt think about that.. thanks for the tip

[racerb]

Originally Posted by Jason@SportsCar

I know some people like to drop the rear pressure to get rotation... But that is not the direction I would go. It makes for unpredictable handling, as the sidewalls wallow, and it kills the outside edge of the tire. If you want to free up the back of the car raise the pressure - it makes the breakaway much more predictable, preserves the edge of the tire, and effectively increases rear spring rate which helps keep weight on the front tires.

In the B-Spec Yaris we are running 36psi cold (Goodyear Eagle RS DOT R race tires) all the way around, we want a hot pressure around 42psi in the front. Alignment is -2.5 camber in the front, with a 1/16" toe out, and the factory alignment in the rear (I think it is about -1 with about 1/8" toe in). The car is very easy to drive this way.

On our Spec-V that weighs 3100lbs and has no camber adjustment, we end up 40psi cold front, and 60psi rear to get the balance we want. We might have gone higher in the rear, but our gauge maxed out at 60psi.

Rice, keep in mind that in Solo you are typically setting to a hot pressure, and bleeding down between runs, on the track you want to hit that same hot pressure, so you have to start lower to allow for tire/temp growth.

Jason is on the money about pressures for a car with stock suspension, my Showroom Stock CRX for example, was usually set at 36-38 cold front and 34-36 cold rear. On most East Coast road courses, our turns and transitions aren't as tight as many in the West, so we usually only gain about 4 psi during a track session. The reason I quoted my Pulsar pressures so low, was that this car ran no front swaybar, inverted Cerrara shocks at full rebound at the rear with higher spring rates and a 3/4" rear swaybar. Without the lower tire pressures, this car would oversteer like a rear drive car all the time, not just when you wanted it to.

He also mentioned the short wheelbase, my ITC Civic 1200 had roughly an 86" wheelbase, making it spin like a top if you ever over drove it into a turn. Believe me you learned very quickly easy throttle control and using the front tires to pull you out of trouble. If you get comfortable enough later on in driving on track with this car, left foot braking can help lower lap times, as I use this technic to make the car rotate and still be able give throttle imput for stability.

Once again good luck and just have fun, it's the name of the game when playing with cars!

racerb