MSR Racer

I run MPSS on 997.1 C4S and they are at 44/37 as per factory specs on the street.

On track however, I did not have good parameters. After talking to fellow DE drivers and racers I logged my tire pressures cold and hot (after each track session) and also logged the tire temperatures using an infra-red pyrometer.

Tire temperature were measured on each tire in 3 places: outside tread, middle and inside. I have given given my log after 3 sessions. Comments and questions are welcome from fellow track junkies and racers.

The track ran clockwise. Left wheel is outside, more right hand turns.

Spokane5150

This link should help.

http://www.trackpedia.com/wiki/Tire_pressure

MagnusB

Overall hotter on the inside, what camber settings do you have?
I usually look at pressure and you're fine.

MSR Racer

pretty good bit -2.

mdrums

Infrared thermometers do not work for taking accurate tire temps
Did you come off a hot lap straight into the hot pit lane and do tire temps?

31/38 hot is too much variance in pressure from front to rear.

MagnusB

Ok, the temp suggest you either need to drive it harder or you can dial back the camber.
I'm thinking the tires you have are not sticky enough for that camber, perhaps.
And as mdrums said, too much difference in pressure front to back.

What size tires btw?

alexb76

Looks like your rears were under-inflated vs. front. You should have the same PSI difference as factory spec. So, you could have started the cold rears a bit higher and that might have changed how hotter fronts got vs. rears.

BTW, what's your alignment numbers? I also got a C4S, and wanna get it aligned, but I can't find factory spec *sport* setting for C4S (C2, Turbo easily available).

MSR Racer

Thanks guys. I will try to answer everyones questions.

I measured the temp in the paddock. Yes the tires had cooled quite a bit.
Hot pressures were 38/42 front/rear consistently. I started with 31/36 cold. I ran them pretty hard although this is arguable.

I have Bilsteins and sway bars on and had track alignment done recently by local Porsche expert. Camber numbers -1.5/-2. i will check with again for you but this is not going to applicable to your car obviously.

As a matter of fact, local Porsche dealership had no idea what factory sport specs are!

Also note that in the chart, I wrote down the temp numbers as if you were looking down on the for wheels from above. So outside number is outer tire-tread temp and inside number is inside tread temp on each side each tire. middle is middle!

Take a look at the chart and tell me what you all think. Thanks

zanwar

After a lot of experimentation, I ran my Targa at even pressures all round, 36psi hot, regardless of tire choice. It drove very precisely in that condition. I also ran 33psi hot and there is a little more grip, but the car was a bit soft, a bit loose, you could feel the tire sidewalls flexing. My suspension was all stock except for GT3 LCAs, I ran the same camber as your car.

utkinpol

Try to keep hot pressures within 2-3 psi from front to rear. Do not exceed 40psi hot for rear.
Also, read about what slip angle is and experiment to find how you car reacts to steering inputs at diff pressures and choose what works best for you.

brad@tirerack.com

This feedback is great, as well as the stats. I'm watching to learn from this as well and to be able to spread to other guys.

MagnusB

I have run my car with PSS and I heat them up a bit more than you do.
I can go from 32 rear to 43 as an example and need to let out pressure between runs.

I have attached some standard alignment numbers for reference.