Track tire pressure - at start and finish of session - 986 Forum - The Community for Porsche Boxster & Cayman Owners

rob76turbo · 04-04-2009, 06:11 PM

Getting ready to run my first HPDE with my 01 Box S. Running Toyo 888's on 17" twists. Have the M030 suspension option.

So I am wondering what a good starting and finishing tire pressure is for these cars. What are you starting with and what are you seeing at the end of the session?

Thanks in advance.

944boy · 04-04-2009, 07:15 PM

Don't ever get them above 40psi, they will become grease. I would suggest starting at 35 cold (depending on outside temp) and measure them as soon as you get off the track. I would aim for ~38 hot and adjust based on feel.

rob76turbo · 04-04-2009, 07:31 PM

Quote:

Originally Posted by 944boy

Don't ever get them above 40psi, they will become grease. I would suggest starting at 35 cold (depending on outside temp) and measure them as soon as you get off the track. I would aim for ~38 hot and adjust based on feel.

Front and rear at the same pressure (38 lb)?

Thanks!!

944boy · 04-05-2009, 08:32 AM

Well I am used to running the same size tire all the way around. You might want a little more on a wider tire (rear) and less on the front. I would at least start out the same. If its pushing you can raise the rear a little or lower the front a hair or opposite for oversteer. Whenever you make adjustments, do it in one or two pound increments. Also its good to make note of the outside temp and pressures in a logbook. That way you get a feel for what is working and have to do less guessing in the future. The best way to tell what the best pressure is; is with a pyrometer, but correct readings are an art and that's only truly needed if your really serious and competitive. For most of us, 'feel' of the car, how much the tire is rolling over, and a working knowledge of how the tire behaves can get you quite far.

Sboxin · 04-05-2009, 03:27 PM

I agree with 944boy -- except front =33 and rear =35 cold temps.
The 2 pounds difference between Fr and RR helps with the Boxster balance.
And, try to keep that log of temps and pressures so you can set the pressures at off track hot temps.
The R888's take a couple of laps to heat up, but after that they do stick very well!!!
Keep an eye on your power steering; this can fail and blow PS fluid all over the engine and exhaust if the fluid temps get too high from the R888 tires (look at my previous posts from 2007).

Enjoy!

Ed

rob76turbo · 04-05-2009, 03:34 PM

Perfect. This seems like a good start. Besides running the 888's, I also plan to have Park Place Porsche (DFW, TX) do a 4-wheel alignment. They have set up a lot of Boxster's for the track and I trust Randal Johnson (parts manager and track guru) on his recommendations.

rob76turbo · 04-05-2009, 03:36 PM

Quote:

Originally Posted by Sboxin

I agree with 944boy -- except front =33 and rear =35 cold temps.
The 2 pounds difference between Fr and RR helps with the Boxster balance.
And, try to keep that log of temps and pressures so you can set the pressures at off track hot temps.
The R888's take a couple of laps to heat up, but after that they do stick very well!!!
Keep an eye on your power steering; this can fail and blow PS fluid all over the engine and exhaust if the fluid temps get too high from the R888 tires (look at my previous posts from 2007).

Enjoy!

Ed

Great!! I will keep an eye on this! Since this will be my first event of the year AND the first one in the Boxster, I plan to keep a very close eye on everything!!

timothy · 04-06-2009, 07:37 AM

Are you going to MSR April 25-26?

mdex · 04-06-2009, 08:04 AM

The 1st question is to your experience level overall at the track, and how hard you will be pushing the car. The reason I ask is to see if you will be getting the tires up to optimum temperatures. Less experienced drivers quite often aren't able to get the tires up to proper temps on track and therefore need higher cold pressures.

Per Toyo's website hot pressures should be in the high 30's to low 40's. I would start off all tires at the same pressures, and then get your hot pressures as soon as you get in off track and adjust accordingly.

On MPSC I run between 26 to 28 psi cold all the way around depending on the temperature of the day to archive mid 30 psi hot pressures.

That leads me to think that starting the car at 30 to 33 psi cold all around should work well for you.

Marc

rob76turbo · 04-06-2009, 08:14 AM

Yes, I will be at MSR in April. I do have quite a bit of track experience, I run intermediate with PCA and advanced run groups with other HPDE organizations. So YES!! I do push the tires a bit. I always try to get an idea of the pressure range before I head out. Last thing you want to do is start off way to high or low. And I have found the forums to be a weath of info regarding how to start out, especially when tracking a car for the first time.

timothy · 04-06-2009, 08:27 AM

Quote:

Originally Posted by rob76turbo

Yes, I will be at MSR in April.

See you there. My car is #312.

rob76turbo · 04-06-2009, 06:46 PM

Sweet!! 312 and 313 (my DE number), both boxsters!!! What run group will you be running?

heyjae · 04-07-2009, 09:41 PM

I find that I gain about 7-9lbs cold vs. hot on my NT01s (235/40/18 and 275/35/18). I tested a few variations 2 weeks ago. These are hot temps: 41/41, 41/37, 37/37, 34/37. FWIW, I got the best balance with 34/37 and the worst with 41/37 (twitchy oversteer). Predictable results, but I wanted to actually try them out.

rob76turbo · 04-08-2009, 06:26 PM

I am thinking that April in TX, you get a mixed bag weather and temp wise. It could be hot or cold...flip a coin. I will start off very conserative based on ambient temp at the start of the day and adjust from there.

BTW, I am heading to Park Place Porsche tomorrow to have an aggressive street / track 4 wheel alignment done. I will post the results tomorrow when it is done.