05-09-2018, 09:48 AM | #1 |
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Tire pressure for the track running square set-up?
Reading through the treads seems like people are either running same pressure all around, or similar to staggered specs but with front up a few pounds (something like 38 rear/35 front).
For those running square set-ups, what pressures are you running? (245/40/17, BS-RE-71R) |
05-09-2018, 02:19 PM | #2 |
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Hello ChrisFulton,
I just did a track day and my instructor recommends me to drop the PSI to 32 and let it heat up. While on track after a few runs my PSS 245/35/18 got up to mid 40s and then eventually the car went into limp mode because the tire I guess got too hot and went from green to yellow. Front what I learned doing two days of track, let the pressure down and as you track the car it'll warm up thus increasing tire pressure. I believe if I went in at 38 I would be getting close to the limit of PSI for the tire after a few laps. I hope this helps! |
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05-09-2018, 02:44 PM | #3 |
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I think that the type of tire is also very important - racing tires (or the streetable track tires) seem to have different recc's and different heat gain vs street tires like the PSS or ContiSports. FWIW, I was not seeing nearly as much temp gain as you were, but only did one track day and I'm quite sure I wasn't pushing the car nearly as hard as somebody who knew what they were doing. Brake heat is a big factor too, both intentional and from the DSC/nannies kicking in - some tell me that the better you drive, the LESS heat you get, since you aren't always triggering the stability control braking. I started at 36 and they went up to 41, which was right about where I'd intended - others were reporting the kind of gains you noted, of 8-12#.
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05-09-2018, 04:47 PM | #4 |
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RE-71s should run around 35 - 37 psi hot. I would probably drop it to 29 cold and let it heat up.
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05-09-2018, 10:27 PM | #7 | |
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When you get ready for your first session of the day, set them at 32 psi, (presuming you've been stopped for a couple hours) and adjust accordingly based on the HOT readings. I always end up lowering pressures as the day goes on to maintain the 38 hot. |
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05-10-2018, 01:00 PM | #9 |
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Absolutely. Front right if going CCW or front left if CW will be hottest. Be mindful of the side to side pressures since that has the largest effect. I'd drop it to 35psi hot all the way around btw.
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05-10-2018, 11:15 PM | #11 |
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Had an EXCELLENT track day on the new square set-up. Tires really stuck and I still feel that I can push them further. OEM brakes & fluid is now a limiting factor with the tires.
capt_and was spot on with advice. In fact, I should have started with 28psi or perhaps even lower. GREAT day and I learned a lot. Thanks for everyone's help here with their suggestions/knowledge. Cheers |
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05-11-2018, 08:00 AM | #12 |
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This is great information. I have my first track day coming up the end of the month. I'm really looking forward to it.
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05-11-2018, 08:36 AM | #13 |
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05-11-2018, 11:32 AM | #14 |
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05-11-2018, 01:44 PM | #15 |
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Tire pressures are one thing but there are lots of other things you should take note of at the track as well you should start making a habit out of. Start with marking your tires with a chalk at the corner where your tread and sidewall meets to see how much rollover you're getting. You should also ideally use a pyrometer to see what temps your tires are at inside, center, and outside tread. This will give you information on not only tires but also your alignment and driving.
Anyway, you shouldn't be in the upper 30s with the current gen tires, and I'd limit it to no more than 35psi hot. Depending on the conditions and the type of racing, I will have anywhere from 31-35, but usually hover around 32-33 with the rears having a hair less pressure. Start at upper 20s so you can warm up the tires a bit faster and take out less at the end of the session. After 3 sessions, your pressure should start to level out so until then you'll need to be checking pressure each time you're off the track (and before, just in case). At the end of the track day, you should refill your tires (should now be mid-20s cold) to the appropriate pressure before driving on the streets. |
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05-16-2018, 11:02 PM | #16 |
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chalk marks and warning triangles?
Wish I had read this thread before my track night last night. I was using my brand new RS4's. I had done a track event on my MPSS, and even with the fronts at 38psi cold, the rollover was really trashing them out. So, I was a bit paranoid about starting with lower (<35psi) pressures on these new tires.
So, for this event I started with 35psi cold all around. Hot pressure at the end of the session was around 46psi. After reading this thread that's obviously way too high. (My mind is so numb after the session I keep forgetting to hit the display to check/record the tire pressure temp. Need to get better at that. The one time i remembered I was amazed the fronts were still at 170° after being off the track 10 minutes.) I did chalk the tires, and was checking that and the little triangle markers on the side of the tire. This is a picture of the right front, the worst, at the end of the day. You can see a bit of the chalk still left on the ridge below the triangle, and some very light scuffing, so I was occasionally getting some rollover. But the wear triangle had very little wear. The chalk wear was similar across all tires, but the triangle was almost untouched on the rears, and less on the 'track inside' side of the car. So, even though the chalk was scuffed off, does the very light triangle wear indicate I had the pressures too high? Would a too high pressure cause an overall loose feeling from the tires? |
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05-20-2018, 10:27 AM | #17 | |
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05-20-2018, 09:45 PM | #18 | |
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I was running 40 when they were hooooot. I still just barely heated the tread up to the tip of the triangle wear indicators. Honestly I wasn't super impressed with the rs-4s.... But I only have 4 hpde events under my belt. I was running faster lap times with my staggered setup 235/40/18 and 265/35/18 mpss |
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05-20-2018, 09:52 PM | #19 | |
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I was lowering pressure all day and think I ended at about 40 hot. The tires sounded like they were rolling, but they basically looked exactly like yours. Maybe a hair closer to the triangle And yeah tires seemed to stay hot for a long time. |
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05-20-2018, 10:13 PM | #20 | ||
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Rs4s will do better than pss as they have stiffer sidewalk but you won't be able to prevent them from rolling by just raising psi and raising the psi will make them greasier. Those should run 34-35 hot |
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05-21-2018, 06:25 AM | #21 | |
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I've got -2F and -1.7R for camber right now. |
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05-21-2018, 09:02 AM | #22 |
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Another reason why you are getting sidewall wear is because of the body roll - the car has lots of it. I am running -3.5* front and 2.2* rear camber and am still getting wear patterns indicative of too much roll. Whenever I only had -2.5* camber front, I would be riding on the letters. We chalked 3/4 way down on the side wall and none of it was left after the session.
RS4s are very good tires. Very sticky for how durable they are. If they are wearing too low on sidewall, try increasing pressure. But, tire pressures can only do so much without some pretty aggressive camber settings on this car.
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