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Tire pressures FS with oem tires

irally

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Hi all,
I have a 2017 GT PP that I plan to do some autoslalom events with. Will run the P Zeros for this year. Any suggestions for tire pressures, first time running a Mustang. Previous car a 2015 VW GTI PP so this is a totally different beast.

Thanks

Dave
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jdub.csu

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38 front 34 rear to start mark with chalk if you don't have a tire temp prob. Adjust temps as need as tires heat up
 
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irally

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Thanks for the suggested pressures. I will try these at the next event, this coming Saturday.
 

Static_LV

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The sweet spot for me seemed to be at 36F / 32R.
 

MrMagnetic

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I found I go faster at 34-35 psi in the front than I did at 38 psi. Around 33 psi in the rears works well. I was advised by a more experienced driver to set the rears 2 pounds less than the fronts and that seems to work for me.

I spray the tread with water between runs to help cool it down.
 

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jdub.csu

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I found I go faster at 34-35 psi in the front than I did at 38 psi. Around 33 psi in the rears works well. I was advised by a more experienced driver to set the rears 2 pounds less than the fronts and that seems to work for me.

I spray the tread with water between runs to help cool it down.

Idk how your not rolling over the front at that pressure.
 

kz

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Idk how your not rolling over the front at that pressure.
?? I typically run 32 front on 275 RE-71R and I am not rolling anything.

If you have 285 squeezed on 9" rim I can see how this possibly can be too low...
 

F0J

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Depends on a bunch of stuff like ambient temp, driving style, braking, tire load, sidewall, driving speeds, mileage, etc.

Some things to keep in mind:

More pressure for more load. Since our cars are front heavy, the front tires carry more load (generally but especially true for braking on a stock chassis).

Tires have an optimal temp, not an optimal pressure. The lower the pressure, the bigger the contact patch, the quicker the tires heat up. So for autox (slower and quicker runs), you could probably get away with lower pressure for more grip.

Any recommendations outside manufacturer spec would be "risky". Pirelli states max 50 PSI which is crazy high. Typically, 32 PSI is a common minimum. So for a quick spurt of grip, you could probably go slightly lower than 32 PSI *cold* but then consider re-inflating your tires for your ride home.

I don't know about "squirting the tires with cold water". If anything on a colder day you want to get tire warmers/coats to keep them hot.
 

NightmareMoon

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Depends on a bunch of stuff like ambient temp, driving style, braking, tire load, sidewall, driving speeds, mileage, etc.

Some things to keep in mind:

More pressure for more load. Since our cars are front heavy, the front tires carry more load (generally but especially true for braking on a stock chassis).

Tires have an optimal temp, not an optimal pressure. The lower the pressure, the bigger the contact patch, the quicker the tires heat up. So for autox (slower and quicker runs), you could probably get away with lower pressure for more grip.

Any recommendations outside manufacturer spec would be "risky". Pirelli states max 50 PSI which is crazy high. Typically, 32 PSI is a common minimum. So for a quick spurt of grip, you could probably go slightly lower than 32 PSI *cold* but then consider re-inflating your tires for your ride home.

I don't know about "squirting the tires with cold water". If anything on a colder day you want to get tire warmers/coats to keep them hot.
The water thing is if the tire has been heated up beyond it's optimal temp, then guys spray them with water to cool them back down between runs. Basically if its too hot to touch, it may be overtemp.

Even in 100 degree heat, you need to be running in a lot of runs with a short interval to get tires overheated at an autox. Autocrossers go a bit overboard with the water spray IMHO, and it isn't needed nearly as often as it is done. One of the locals even would argue that by spraying too often, you're adding unnecessary heat cycles to your tires.
 
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MrMagnetic

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Idk how your not rolling over the front at that pressure.
I chalk the tires regularly and don't see much more rollover at 35 pounds than I did at 38. I was using 38-40 pounds in the front and I was much slower than similar cars. A faster driver advised using less pressure and my times drastically improved.
 

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jdub.csu

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If we are talking FS SCCA specs I just don't see it unless you like chewing up your sidewall. 35 would be as low as I would go in the front. We just don't have the camber we need in FS which is why I'm going to camc lol
 

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I don't do autocross, but I have done a few HPDE events on the stock Pirellis. I found that once the front tires hit 37 to 38 PSI, I was starting to loose some grip. I tried to keep them in the 34 to 36 PSI range with 2 to 3 pounds less in the rear. That seemed to be the happy spot.
 
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irally

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Hi All,
Thanks for the replays.
Was at an autoslalom today and ran the tires 32f and 29r hot. These pressures seemed to work well 2nd in class by 0.04 to a BMW 3?. No roll over onto side wall, air temp 26c, limiting factor driver and I didn't turn off all the nanny. FTD was 34.8?? my best time was 40.062.
 

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Last event I ran I watched tire pressure (no heat probe yet). I aired the tires down to 31/30 cold on my gauge which showed 33/32 on the sensors, and drove to the event (about an hour). It was a very hot day - about 93 ambient. Didn't check pressure once there.

We do two three run sessions for each heat; three heats in the AM; three in the PM. After my first three runs, pressure was up to 36/34 on the gauge and nearly 40 on the sensors. Traction was gone, especially in the front. For the PM runs, I aired down the tires to about 31/30 on the gauge and went out. Big difference. Ran my best time right out of the box; thereafter I took out cones.

These P-Zeros had about 16K on them, with several A/Xs and one track day. In preparation for an open track day, replaced the P-Zeros them with some MPSS.
Rears were down to the wear bars; fronts were way past the bars.
 

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Last event I ran I watched tire pressure (no heat probe yet). I aired the tires down to 31/30 cold on my gauge which showed 33/32 on the sensors, and drove to the event (about an hour). It was a very hot day - about 93 ambient. Didn't check pressure once there.

We do two three run sessions for each heat; three heats in the AM; three in the PM. After my first three runs, pressure was up to 36/34 on the gauge and nearly 40 on the sensors. Traction was gone, especially in the front. For the PM runs, I aired down the tires to about 31/30 on the gauge and went out. Big difference. Ran my best time right out of the box; thereafter I took out cones.

These P-Zeros had about 16K on them, with several A/Xs and one track day. In preparation for an open track day, replaced the P-Zeros them with some MPSS.
Rears were down to the wear bars; fronts were way past the bars.
I think I have been running way too high of pressures (done to keep from rolling onto the sidewall). Last time out I was running 36-37 front and 31 rear. I'll try 31-32 and 30.

I'll have more front camber for the next time out so that should make it a lot easier to do.
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