| Author |
Message |
Peter S�derlund /328 GTB -88 (Corsa)
Junior Member
Username: Corsa
Post Number: 225
Registered: 4-2001
| | Posted on Monday, July 29, 2002 - 2:11 am: | |
I have seen maximum 8,7 psi and minimum 4,5 psi difference between cold/hot. That's why I don't consider the setting of cold pressure as valuable, especially because the ambient temperature has some influence on it and you generally don't know how "cold" your tires are. After driving to the track they are not very cold, rather semi hot. I normally check the cold pressure when ambient temperature is from 50-85 degF.
I believe that you first check your pressure after a hot stint and try to evaluate the cars grip and handling. Check the pressure just before the next stint to see how much the pressure has decreased in between. Then you know something at least and can set your pressure just before you go out for the next stint. After all, it's the pressure when driving (i.e. hot) that's the important pressure.
Low pressure
More grip (faster) and sloppy handling (slower)
Higher pressure
Less grip (slower) and better handling (faster)
Funny, isn�t it?
Oups, Just read Mitch's and Roger's comments.
Ciao
Peter |
acw (Acw)
Junior Member
Username: Acw
Post Number: 79
Registered: 2-2002
| | Posted on Saturday, July 27, 2002 - 9:52 am: | |
Thanks for all the input. I'll definitely listen / adjust the pressure during the day.
Jack, you are correct, I did not trust Ferrari's number because Porsche's number are usually optimized for the road.
ACW |
Steven J. Solomon (Solly)
Member
Username: Solly
Post Number: 341
Registered: 6-2001
| | Posted on Friday, July 26, 2002 - 3:22 pm: | |
ACW- normally you are right, higher pressures in rear. However with the P-Zeros it is 32 front, 29 rear. I don't know why,possibly due to the weight of the engine on the rear?
I have tracked the cars at Pocono, Lime Rock, Moroso, and plan on the Glen on Labor Day. |
Roger Arlen (Rogera)
New member
Username: Rogera
Post Number: 5
Registered: 5-2002
| | Posted on Friday, July 26, 2002 - 2:09 pm: | |
Using the recommended cold pressure is the best place to start. Whether that is the ultimate optimal pressure will depend upon how hard you drive the car as well as the ambient and track temperature on the date/time you run. I ran my 360 at Thunderhill a week ago and the cold pressure of 29/29 (pilots) was not optimal for the track that day, in part because of the fact that it was 97 degrees out and the track surface was hot. The pressures needed to come down by 4 lbs (hot), but I didn't know this until I was out on the track and the car didn't feel quite right.
It's important to listen to the car on the track and look at the tires when exiting, it will tell you how it would like the pressures adjusted, if you know what to look for. If the car feels a bit "greasy", you probably have a bit too much pressure and you can begin to come down in 1 lb increments until it feels right. Over pressured tires will also tend to not show wear to the sidewall rollover arrows that are present on most high perf tires.
If the tires don't have enough pressure you can actually feel and sometimes hear the sidewalls "rolling over", and you'll see that tire wear has surpassed the tread wall indicators.
Investing in a good tire gauge and getting comfortable with cause/effect on tire pressures is the most rewarding technical investment I've made into my track hobby. It is remarkable the difference that 2 pounds of air up/down can make in the performance of the car and my enjoyment/speed on the track. I approach the first session of the day as a giveaway during which I'm very comfortable coming on/off the track 2-3 times in order to get things right. It is well worth over the course of the day.
|
Jack Fried (Jack360)
New member
Username: Jack360
Post Number: 17
Registered: 6-2001
| | Posted on Friday, July 26, 2002 - 1:00 pm: | |
Arnaud:
As Viken suggested, run the factory recommended cold pressures (as stated in the manual) for the specific tire on your car -- it will work great for the track. You'll end up just shy of 40lbs when hot if you're running hard. Ferrari gives you meaningful recommended tire pressures unlike Porsche (inside joke for us 996tt owners). :-) |
acw (Acw)
Junior Member
Username: Acw
Post Number: 77
Registered: 2-2002
| | Posted on Friday, July 26, 2002 - 12:38 pm: | |
So is it 29Front-32Rear or 32-Front 29-rear?
There is usally more pressure on the rear right?
Thanks
ACW |
Willis Huang (Willis360)
Member
Username: Willis360
Post Number: 815
Registered: 8-2001
| | Posted on Friday, July 26, 2002 - 12:37 pm: | |
I got the Michelin Pilot Sport. The numbers are accurate. Speaking of tires, I'm gonna need fresh ones soon. |
acw (Acw)
Junior Member
Username: Acw
Post Number: 76
Registered: 2-2002
| | Posted on Friday, July 26, 2002 - 12:34 pm: | |
It is normal for them to be lower for track use. Usually, there is about 8psi difference between hot and cold on the track. At least that's what I have seen on my other car.
Thanks for the data!
ACW |
Tim N (Timn88)
Intermediate Member
Username: Timn88
Post Number: 1328
Registered: 6-2001
| | Posted on Friday, July 26, 2002 - 12:32 pm: | |
those all seem low. i thought you would want them in the mid to high 30's. |
Viken Bedrossian (Vikenb)
Junior Member
Username: Vikenb
Post Number: 177
Registered: 5-2001
| | Posted on Friday, July 26, 2002 - 12:12 pm: | |
>> Thanks Steven. That's 29-32 cold right? <<
- Goodyear Eagle F1 Fiorano: 32F / 32R
- Pirelli P-Zero System: 32F / 29R
- Bridgestone Potenza S02A: 32F / 32R
- Michelin Pilot Sport: 26F / 28R |
Mitch Alsup (Mitch_alsup)
Junior Member
Username: Mitch_alsup
Post Number: 89
Registered: 4-2002
| | Posted on Friday, July 26, 2002 - 11:05 am: | |
Tire pressures are always set cold--but you should take you tire pressures just after you get off the track 1) to see what pressures you were running on, 2) and to help you decide whether to increase or decrease pressure and 3) on which end.
Dont set the pressures until just before you go back out onto the track. |
TomD (Tifosi)
Intermediate Member
Username: Tifosi
Post Number: 1116
Registered: 9-2001
| | Posted on Friday, July 26, 2002 - 11:02 am: | |
tire presurres are always done cold |
ELI (Titanium360)
Junior Member
Username: Titanium360
Post Number: 89
Registered: 4-2002
| | Posted on Friday, July 26, 2002 - 10:53 am: | |
Steven:
Where do you track your car locally? |
acw (Acw)
Junior Member
Username: Acw
Post Number: 75
Registered: 2-2002
| | Posted on Friday, July 26, 2002 - 10:36 am: | |
Thanks Steven. That's 29-32 cold right?
ACW |
Steven J. Solomon (Solly)
Member
Username: Solly
Post Number: 340
Registered: 6-2001
| | Posted on Friday, July 26, 2002 - 9:55 am: | |
P-Zeros should remain at the stated pressures whether road or track. I run my 360 on track with the same tires at 29 front 32 rear. Wonderful handling. Non-Z rated tires should be bumped up 5-7 psi depending on the outside temperature. |
acw (Acw)
Junior Member
Username: Acw
Post Number: 74
Registered: 2-2002
| | Posted on Friday, July 26, 2002 - 9:40 am: | |
I'm going to Willow Spring next week and was wondering if any of you has a recomendation about the tire pressure (front / back) I should use at the track. I'm using some P-Zero tire.
Thanks
ACW |