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roxstuff
03-04-2008, 06:31 PM
I am going to Summit in 2 weeks to do the NCCBMWCCA 2 day driving school. Today I mounted a new set of Falken AZENIS RT-615 205/50R15 on Team Dynamics Pro Race 1.2 - 15x7 wheels. I will be using these for both days of driving. I plan to – scruff - them a bit before track day (under the cloak of darkness!!). My 87 325 IS / E30 has the suspension done to Spec E30 with Bilsteins and H&R springs, and centered urethane control arm bushings. I have new ATE rotors and I am using Hawk Plus pads. The rest of the car is mostly stock with new exhaust, belts, fluids, hoses, clamps, filters etc.

Now what would you consider a good tire pressure to start off the Summit session with considering this setup?
Any tips for hot or cold temps?

Thanx
John

mcoupemindy
03-05-2008, 06:29 AM
I am going to Summit in 2 weeks to do the NCCBMWCCA 2 day driving school. Today I mounted a new set of Falken AZENIS RT-615 205/50R15 on Team Dynamics Pro Race 1.2 - 15x7 wheels. I will be using these for both days of driving. I plan to – scruff - them a bit before track day (under the cloak of darkness!!). My 87 325 IS / E30 has the suspension done to Spec E30 with Bilsteins and H&R springs, and centered urethane control arm bushings. I have new ATE rotors and I am using Hawk Plus pads. The rest of the car is mostly stock with new exhaust, belts, fluids, hoses, clamps, filters etc.

Now what would you consider a good tire pressure to start off the Summit session with considering this setup?
Any tips for hot or cold temps?

Thanx
John

John,

It's honestly going to be "what feels best." I've used several sets of Azenis' on all my BMW's and they all seem to like ~2-3 psi above recommended pressure.

Just my diminishing $.02.

roxstuff
03-05-2008, 06:46 AM
so i,m thinking 35 psi or so to begin?

mcoupemindy
03-05-2008, 06:53 AM
so i,m thinking 35 psi or so to begin?

I think 35-36 psi should be a good starting point.

Nick325xiT 5spd
03-05-2008, 01:13 PM
35PSi is a good starting point. Measure the pressure after each session. Depending on how hard you drive, that may work, or it may be WAY too high. It's much better (and safer) to start high and work your way down, though.

Bimmer3
03-05-2008, 04:56 PM
Agreed, 35 psi (cold) all around is a good starting point. When I was autocrossing a 325is years ago, I always had about 2-4 lbs. more in the front than the rear, but that was to get the best turn-in response and sidewall stiffness out of them. They will go up about 3-7 lbs. in a session on the track, so monitor them, but don't bleed out too much air, then they will feel sloppy. Remember to bleed a little out before driving home, otherwise the car will ride a little rougher then normal. Check them again Monday morning after the school, and add air to bring them back to regular pressures. The important thing is that they enough air so you don't get unusual wear, and that you learn how to drive them at the school. Be the tires, nah nah nah nah nah...

See you Saturday, 3/15
Brian Hair

fitzhugh
03-05-2008, 07:54 PM
Another tip...

Check your pressures after the first session and you'll find the left side is higher than the right. That's 'cause the left (outside) tires are hotter. I generally equalize the left/right pressure after the first session - although I've heard some say you want more pressure in your outside tires. Any comments?

Neil
03-06-2008, 11:49 AM
FWIW, I adjust tire temps so all 4 tires rise to same hot temperature.

Neil

fitzhugh
03-06-2008, 12:37 PM
Yeah, I agree. I know most of the turns are right (at Summit, Main Circuit), but there are left turns too. And I want the car to handle the same regardless of which way I'm turning. Maybe I'm just funny that way.

roxstuff
03-06-2008, 09:19 PM
I appreciate the suggestions and tips. I have noticed that this is one topic that does not get down to real numbers in any of the forums I have searched and that I follow. Almost like it is a secret that drivers/racers do not want to reveal . . . .

Anyway thanks all for the tips. I will be sure to re-post with findings from the "real world" after track days in case anyone is interested.

John

1996 328ti
03-06-2008, 09:34 PM
There are no real numbers. It depends on the car, tires, driving style.
I try to get my RA1s to 40 pounds. I start at 33F and 34R with an ambient temp in the 60s.
Someone who is more aggressive than me can probably start even lower.
If it's raining or cold, I start higher.

I know people say you can't get accurate results unless you have a pyrometer, but I try to measure the air as soon as I get off the track. Rarely does that happen since a good instructor will give you a debrief of your session.

fitzhugh
03-07-2008, 12:10 PM
Steven is right on. There's no "secret" anyone trying to keep, the numbers are just so variable. You'll have to experiment to discover what's right for you (your car, your tires, your modifications, your driving style, etc.) Your instructor will be helpful in this matter, so be sure to bring up the subject with him or her. If you're lucky, you'll have it sorted out by the end of the first day.

1996 328ti
03-07-2008, 12:22 PM
If you're lucky, you'll have it sorted out by the end of the first day.Took me +4 years. :biggrin:

roxstuff
03-08-2008, 10:38 AM
Again thanx for all the tips.

I hope I didn't offend anyone with the use of the word "secret" in previous post. I was not implying anything other than the actual numbers are hard to find in forum posts. I only have time to follow 2 forums, here at the NCCBMWCCA and the SpecE30. I have found everyone at both places to be extremely helpful and always eager to share tips and suggestions. I have high respect for people at both forums as a result.

I have also found most all drivers at the track be as friendly and willing to share information.

Thank you again, see you next weekend.

John

e30m3sm
03-08-2008, 11:20 PM
Most R compound tires like to be at 40 psi HOT while street tires can only go up to 38 psi HOT. AutoX'ers tend to use higher pressures but a 35 sec run is different from a 25 min. session. Remember PV=nRT so longer sessions gives us more of the T (as in temp)

As has already been posted, check your pressures coming off the track. If they are higher than this bleed them down and then recheck them cold and you will have your answer.:)

Gerry

roxstuff
03-17-2008, 12:27 PM
Well the numbers provided by you all helped greatly.

I started Saturday morning with 35 psi in all four tires. End of first session I checked and pressure was 40 on the left side and 39 on the right side. Car sat for bit before next session and when I checked, there was 37 psi in all four tires. After the next session 40 on left, 39 on right. Being a wise student I checked before and after each track session and each time the same results. Even Sunday with weather a bit chilly I got same results. After the runs 40 left side and 39 right side, cool down to 35 to 37 all around between runs.

Lather, rinse, repeat . . .
Needless to say I never added or took off air all weekend.

Thanks again for the tips.

John