sorry if its a repost but....

1. What tire pressure should i be running my 18" cs wheels in 78 deg/ Max. Humidity: 25% weather?

2. When is my 2.7 best balanced? when my tank is 1/4,2/3, 3/4 or full fuled

3. Is 93 octane really going to make a diffrence? (im running 91)

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HP is irrelevant

I've moved this to the Competition Forum where you can find a wealth of information about AX including many answers to your questions.

I'll go at this early and let others disagree.

Tire pressures are somewhat of a personal matter, depending on driving style and how much you want to rotate the rear. I've only autocrossed 4 or 5 times on street tires (I assume you're on street tires), but I start the fronts at about 34# and the rears at about 35. I've been autocrossing for over 20 years, and I still consider starting pressures to be no better than informed guesses. I do know that you'll likely have too much understeer if you go by Porsche's recommendation in front.

The Cayman is best balanced front to rear with a full tank, and the gas won't be sloshing from side to side in turns (and it always moves toward the side you don't want it on). However, with a full tank, you'll also be carrying additional weight (about 6# per gallon). Honestly, I don't know what the optimal fuel load is, even for my own driving style. Consequetly, I run with about a half tank, thus shedding about 48# compared to a full tank.

I've only run 93 octane, so I don't know about a possible 91 versus 93 difference. The Cayman is supposedly tuned so 91 will be sufficient to provide full hp. Even if 93 octane gives a couple more hp than 91, I don't think it would make a noticable difference on an autocross course.

Sean,

We look forward to seeing you at the event tomorrow.

1) If I remember right you are running PS2s. These tires seem to like 38-40 psi hot. Start with 33 front and 34 rear cold and we can tweak it from there during your runs.

2) Do not sweat this too much. Just make sure you have enough fuel to finish the day. I generally try to run light (and I weigh a lot more than you!), but I have also won events with a nearly full tank.

3) Again, do not sweat this too much. If you want to put in a few gallons of 100 for fun go for it, but it will not make much difference.

For tomorrow, just focus on hitting your lines, being smooth and having fun. This will pay far greater dividends than any of the above. Also, take a ride with one of the young hot shoes (Attila, etc.) early in the day. They will show you things that you did not think your car could do.

Cheers,

Now that is the best advice I've seen on the subject.

Higher pressure in steel belted radials = stiffer sidewalls = more traction. Start with your tire's max rating in front and about 5 psi less in the rear.

This rule is for AX where most tires don't run long enough to get to optimum temp. Tires such as Hoosiers, which get to temp incredibly quickly, should be run at pressures that promote optimum temp.

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