Keith Guidus

What do you suggest for tire pressure for an autocross?

fatmike

Such a great question! I"m running AutoX tomorrow for the first time at Pocono. I plan to start with 34 front and 35 rear on my 987.2 Cayman S. 18" with Michelin 4S tires.

I have no idea if that's right or not, but you need to start somewhere and adjust from there.

(I also plan to take out some cones, so I might not be the best person to ask...)

When is your event?

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Racer Boy

No way to answer the question without knowing what tires you are running, the car (year, model), and if the car is stock or has mods.

I'd chalk the sidewalls and inflate to a few pounds over the recommended pressures if using the stock tires. Then after a run check to see how the tire is rolling over and adjust the pressures down until the tire is rolling over to the edge of the tread. If running a race tire (200 tread wear), the sidewall is probably stiffer than stock so you'll have to start out with lower pressures. Ask around to see what other drivers with the same car and tires are running their pressures at.

sasilverbullet

On my 06 Cayman S, with Cayman R suspension and the stock 18" wheels and Pilot Sport 4S, I run what the door sticker says, 30 Fr, 37 Rear. After 2 autox's looking at the "chalk" wear, it's perfect.

fatmike

Good data point thank you.

My door sticker is 30/31.

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Aussie skypig

2006 Cayman S

Door sticker: 30F 37R
interestingly the manual is 1psi different. 29F 36R

I can only dream of being good enough to feel 1psi difference!!

Ric In RVA

Wonder what the Cayman R door sticker says as that is likely to be "more" correct due to the suspension change.

My 2009 base with 18" s wheels .2 cars runs. much lower rear pressures.

sasilverbullet

From what I've watched on youtuber, you know, everyone's an expert! Supposedly you can only "feel" about a 4 psi change. I can feel a 2 psi change easily in my car.

fatmike

Follow up on this.

2010 cayman S. 18” OE wheel. Michelin 4S tires. Window sticker 30F/31R.

I left my garage on the morning and drove (highway) to autocross. So tires were warm but not hot to start. Bled down to 30F/32R or something like that for first run.

Big tire pressure build on the first run and I bled front and rear (more from the front) to get to 34/35 hot.

I bled air after each subsequent run except the last to keep at 34/35.

Car was balanced and chalk showed good wear marks.

I’m not fast at autocross. Plenty of time to gain on getting my lines right, finding acceleration and braking zones, driver inputs, etc. Tire pressure wasn’t the issue!

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Zach L

Sticker on a factory Cayman R is 31psi front and rear. This was likely changed by Porsche due to the thicker rear swaybar that induces a bit more rear slide at the limit than on a base/S.

I run lower pressures than most and find my R does well. It's been enough to win 1st place at two of the last four autocross events I've attended. Typically I start at about 30psi and bleed off as the tires heat up. I'll never go north of 33 or 34. At higher pressures I find the car slides a bit much, feels greasy. This is on a stock suspension R with 200tw tires (RE-71R and RT660), which have stiffer sidewalls than the PS4S floppy flops most are running.

sasilverbullet

I'm about to order a set of Kumho Ectsa VT-07's, heat cycled, from Tire Rack to go on my "autox" rims. 3rd fastest tire according to Tire Rack's videos.
My car has been upgraded to Cayman R suspension, not 100% sure exactly what pieces/parts were upgraded, I'm assuming everything.
I'll probably go with 31/31 to start with and see how it goes. I'll also be adjusting the air pressure between runs.

Sound about right to you?

Zach L

From what I've seen, most who upgrade to Cayman R "suspension" do just the springs and shocks. Some even do just the springs but will typically say "Cayman R springs" if so. It's rare for someone to do the Cayman R rear sway bar upgrade.

sasilverbullet

I'll ping the previous owner, maybe he remembers.

Aussie skypig

My Cayman has H&R sway bars F&R.
I wonder if 31 rather than the originally recommended 37 for the rear might work. Mountain Roads

sasilverbullet

Verified, I have Cayman R sway bars! I'm going with 31/31 next autocross.