Those of you who do HPDE/track, what tire pressures would you recommend for a 3150 lb E36 M3 coupe running square 17x9 245/40 Hankook RS4's? My alignment shop set them to 38lb front/rear when I had my alignment and balancing done recently, but I haven't taken the square setup to the track yet so I thought I'd ask if that sounded reasonable starting point, or if I should bump it up a couple pounds.
I expect the weather to be in the 70's and dry.
1999 M3/2/5 - Titanium Silver - Track/Weekend Toy
What are the alignment specs and spring rates?
S50 M3 / Track
M52 Touring / Street
Too high based on what my RS3s liked, similar weight, try 32-35psi hot assuming you have a good amount of camber
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-Chris
I'd probably start about 28-30 cold and see what that does for you. Hoping to get to the 32-35 hot like ThreeD talked about. At a 38 psi starting point if you are able to get some good heat in them they'll wind up in the 40s and that's way too much for those.
Once you get in that range (32-35) you can play with it to find what works best for you. Temp probe will help immensely.
Chris Leone
chrisleonemotorsports.com
roll cages, repairs and racecar fabrication
1984 318i now 325is
1994 325is STU racecar
1988 325is donor
Here's what I would do on that car with those tires, if I didn't have a proper tire temp probe test setup.
Assuming 30 min. HPDE sessions.
I would set them at 28 psi in the morning before the first session, and at the end of EVERY session all day, right after I got to my paddock spot, I would bleed each tire down to 34 psi. If the tire was below 34 psi when I checked it, I would just leave it alone for that round.
I would keep notes on the process. After a few days on that track with that setup, I would start to get a feel for what was happening on each tire and how fast it was coming up. That would allow me to start dialing in targeted hot temps and actually attain them, so I could experiment with 33 psi vs 35 psi, for example, and pay attention to the handling effects.
At the end of every day after I packed my car, I would hit the air hose and fill them up to a couple pounds over the door sticker figure, for the drive home. And in the morning, before I drove very far, I would pump them up to the door sticker number again, because they would be way low after cooling off overnight.
Last edited by JBasham; 09-07-2017 at 11:49 AM.
If God meant for man to motor-swap LS engines into track cars, He wouldn't have created Corvettes.
^ A very reasonable approach.
Only thing I'd really add to that is to look closely at how much of the tire is being used and to use those wear patterns to adjust. I'm a big fan of getting my pressures set to where I'm using all the tread without rolling over.
1377696716.jpg
Thanks for the pointers.
It ended up being an interesting track day since it decided to pour in the morning and then dried out through the afternoon. I continually checked and lowered pressures throughout the day and the car stayed more or less planted with good wear patterns throughout.
1999 M3/2/5 - Titanium Silver - Track/Weekend Toy
https://driftdialects.com/products/a...nt=41971975054
Does anyone have experience with these? Seems like a great idea if they aren't too big and are accurate.
I use the Carchet brand, you can find them on amazon for $70. Yep they're accurate and work great. Only peeve is, for the square one at $90 they have a temp sensor too, and its max range is 80 centigrade. So they start beeping later in a session. No biggie, you just have to smack a button on the top and it stops. But you have to do it once for each wheel. Next time I'm getting the $70 round one that has no temp sensors. I assume it's as accurate as the square one.
If God meant for man to motor-swap LS engines into track cars, He wouldn't have created Corvettes.
Thanks for the feedback, looks interesting if accurate. Strange they'd put an alarm so low
Temps across the tire should send you in the right direction. Keep notes.
ME:"I want to make my car faster and lighter"
THEM:" Get out and let someone else drive"
And get yourself a quality pressure gauge. Bridgestone had a gauge calibrator at an event once... I tested three gauges of varying quality... I threw two away... even my "good one" reads about 0.5 psi low but that's close and consistent.
Lime Rock Park... the most fun you can have in a mile and a half.
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If the temps in the center of the tire are higher than the edges, then you have too much pressure.
Starting at 38psi cold sounds like WAY TOO much pressure to me.. that should put you well over 40psi hot.
I have some camber plates in the front and with the pressure right I have really even temps from left to right on the tire. This also makes for much more even tire wear.
https://www.amazon.com/Nubee-Non-con...tire+pyrometer
Last edited by MemphisRob; 11-20-2017 at 11:00 PM.
Yep, spot on there. You want to see an even distribution of surface temps at middle and edges of the carcass.
Exactly! If you don't see a 5-7 psi increase from COLD to HOT pressures then you aren't pushing the car.
Exactly what we tell people - to save their tires from this...
Without additional negative camber even the "best" suspensions BMW makes can and will shred the outside of the front tires.
I like to see McStrut cars running at least -2.5° camber up front for track use. This saves tires from premature death. For many track BMW drivers camber plates are the FIRST mod, sometimes the ONLY mod.
With the right setup the camber plate wont alter your ride height from stock, up or down. Of course with coilovers that no longer becomes an issue...
Terry Fair @ Vorshlag Motorsports
2001 Steel Gray MCoupe - 147,000 miles and owned since new. MCS 2WNR suspension, Hotchkiss swaybar, poly bushings all around, cat delete headers with custom tune, 3.73 LSD, and Clownshoe Motorsports rear subframe reinforcement.
2014 Porsche Cayman S / 2022 BMW X3M Competition / 2020 Ram Rebel
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