| Author |
Message |
Rob Schermerhorn (Rexrcr)
Junior Member
Username: Rexrcr
Post Number: 162
Registered: 11-2002
| | Posted on Monday, January 27, 2003 - 10:18 am: | |
David, I agree with Rob L's advice. Try his cold pressures to start with, 34 front, 32 rear. Expect pressures to rise due to the carcass flex that Lawrence describes perfectly. This will give you a nicely balanced place to start, and depending on preference and experience, you may not want to deviate from this setting.
Ferrari recommended cold tire pressures you quote will result in frustrating understeer for sure. Remember to reset to the factory settings when leaving the track, though. Compensate for temperature by adding four psi if the tires are 1600F or more.
Also, at the track, it's easier to start too high and bleed pressure than too low and add, unless you bring your own nitrogen bottle, hose and regulator. Be careful of service station air that contains excessive amounts of water. Test by "bleeding" the tire chuck with your air gauge to see how relatively dry the compressed air is. |
Lawrence Coppari (Lawrence)
Member
Username: Lawrence
Post Number: 481
Registered: 4-2002
| | Posted on Sunday, January 26, 2003 - 8:24 am: | |
The amount of pressure rise is dependent on the initial pressure of the tire. The tire gets hot because of its flexing. If it is higher pressure to begin with, the temperature rise will be less. If the tire pressure is lower, there is more flexing and more heat buildup so there is a greater temperature rise.
The temperature rises until the amount of heat given off by the tire to the air equals the amount of heat generated by rubber flexing and heat conducted in due to brake use. So what you do is use less pressure in colder weather, more pressure in warmer weather. Given similar driving style, the peak pressure should be about the same. But tire temperature will differ.
You have to decide what temperature allows your tires to work the best for you given your spring rates and track surface. It is a complicated situation. In general, a few pounds over the recommended factory recommendation is a good starting point. |
Rob Lay (Rob328gts)
Board Administrator
Username: Rob328gts
Post Number: 3346
Registered: 12-2000
| | Posted on Saturday, January 25, 2003 - 10:54 pm: | |
Be careful as you can expect the pressure to rise about 5 during the session. If your end target is 35 to 38 I would start 30 to 33. Try different settings, I usually put more pressure in the fronts as that will give you more steering. If it feels nervous, then you might take some out of the fronts. I tried 34 front 32 back last time and it worked well. |
David Reaburn (Dreaburn)
New member
Username: Dreaburn
Post Number: 2
Registered: 12-2002
| | Posted on Saturday, January 25, 2003 - 10:25 pm: | |
Can anyone suggest the best tyre pressures to run on a track day? I have an '89 328 with Michelin MMX's. User manual suggests 33 & 36 front & rear but that's for Goodyear Eagles. I'm guessing i should go a bit higher than this.
Thanks in advance. |
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