Tires pressures for the track.

rick shea

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I have a 2019 GT350R. I have Michelin Pilot Sport 4S on my car and intend to use them on the track for DE days until they wear out. There has been a lot said on this site about the importance of tire pressures for the best handling. The tires have 2,300 highway miles on them mostly from driving the car back from the dealer I purchased the car from in the midwest. I am in Seattle. I am running the tires at the OEM recommended tire pressure for the street. I am getting ready for my first DE season for the car and would like some advice and some experience with the PS4S's on the R and what seems to be the optimal pressure once the tires have heated up. The car alignment is set up for the track so I want to maximize my fun with the best possible handling...and no, at least for now I am not going to rum the Cup2 tires that came with the car. I do use the car around town also and took the Cup 2's off as they weren't very comfortable (tram lining) around town and in the rainy weather.
What PSI should I look to target on the track at temperature on the PS4S's?





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svassh

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I ran those on my 2018 GT350 at my only 2 day track session. Started with 30 PSI but as I got faster I had an instructor that also ran a GT350 advise me to drop to 28 PSI. I could tell a difference. Have not tracked my GT350R yet but it will be on the Cup 2s when I do.

I would start at 28 PSI and see what they rise to when you end a session.
 

nordique14

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Over at TMO, on guy on 4S tires tried all sorts of pressures and swears that 34 hot was the best temp. Ford Performance recommends 38f/36r hot (for PSC2).

so basically, there are a lot of opinions and not much consensus.
 

meterman

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I have a 2019 GT350R. I have Michelin Pilot Sport 4S on my car and intend to use them on the track for DE days until they wear out. There has been a lot said on this site about the importance of tire pressures for the best handling. The tires have 2,300 highway miles on them mostly from driving the car back from the dealer I purchased the car from in the midwest. I am in Seattle. I am running the tires at the OEM recommended tire pressure for the street. I am getting ready for my first DE season for the car and would like some advice and some experience with the PS4S's on the R and what seems to be the optimal pressure once the tires have heated up. The car alignment is set up for the track so I want to maximize my fun with the best possible handling...and no, at least for now I am not going to rum the Cup2 tires that came with the car. I do use the car around town also and took the Cup 2's off as they weren't very comfortable (tram lining) around town and in the rainy weather.
What PSI should I look to target on the track at temperature on the PS4S's?
I heard that 28 psi is the starting point. I won't be hitting Mid-Ohio until June but I can let you know after that.

Jim
 

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so basically, there are a lot of opinions and not much consensus.
because PSI is not a reliable indicator. Get an IR gun, take the temps of the tire. Adjust air till the tire gets up to optimal temp. Adjust air to keep it from exceeding temp.

If you measure PSI, be sure to use the same gauge for consistency but your run of the mill is only accurate +/- 2% if you're lucky. Spend $200 and get a certified unit if you're going to play PSI games.

sidewall construction, camber settings, sensitivity of butt-o-meter, heat cycles on compound, age of tire all factor in. One man's "hot" temp is another guy's "cold" because the one driver puts far more load into the carcass.
 

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Over at TMO, on guy on 4S tires tried all sorts of pressures and swears that 34 hot was the best temp. Ford Performance recommends 38f/36r hot (for PSC2).

so basically, there are a lot of opinions and not much consensus.
Uep that is me :)
34 seems the good HOT target.

As someome suggested.
Start 30psi cold run first session and measure pressure again and adjust.
I now start at 27-28 but my speed is now increased. A lot.
So 30 is a good way to start.
Remember
At 30 grip is not great. Give 1 or 2 laps with good speed to warm up them
 

tbr2001

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I've had luck following the 350 supplement documentation...28 cold on my Cup2s.
 

firestarter2

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Over at TMO, on guy on 4S tires tried all sorts of pressures and swears that 34 hot was the best temp. Ford Performance recommends 38f/36r hot (for PSC2).

so basically, there are a lot of opinions and not much consensus.
I run 32 hot on the psc2.
 

jmn444

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because PSI is not a reliable indicator. Get an IR gun, take the temps of the tire. Adjust air till the tire gets up to optimal temp. Adjust air to keep it from exceeding temp.

If you measure PSI, be sure to use the same gauge for consistency but your run of the mill is only accurate +/- 2% if you're lucky. Spend $200 and get a certified unit if you're going to play PSI games.

sidewall construction, camber settings, sensitivity of butt-o-meter, heat cycles on compound, age of tire all factor in. One man's "hot" temp is another guy's "cold" because the one driver puts far more load into the carcass.
IR gun isn't the way.... probe pyrometer is. I know tire's have optimal operating temps, but i've never heard of using air pressures to avoid exceeding them, can you explain this?

I thought the goal was to get even temps across the contact patch to show that you are using the full patch available grip... also pretty sure you have to dial in the "right" camber this way before it works correctly for pressures too.... IE assuming contact patch is right mechanically, then too much pressure would show center as being hotter from being ballooned outward, while too little pressure would show outside and inside as hotter than the center.... if not enough camber, outside will always be hotter regardless of pressure, if too much camber the inside will be hotter....

34 hot seems like a reasonable starting point though to me though, adjust till you end sessions at that, then if you are a consistent driver drop it 2 psi and see if lap times go up or down and if you notice any change... try 36 and see the same...

it's a bit less critical to get pressures and camber perfect on a street tire since they wear out a lot slower.
 

shogun32

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IR gun isn't the way.... probe pyrometer is.
fair point. The IR is considerably faster but only a partial answer. A good Pyro is several hundred. My larger point was temperature is what matters, not PSI. Evenness across the tire is good obviously. Running a higher pressure (within reason) and depends on how hard the tire is being worked (squirm) help to keep the rise in check. Till you get to the point where now you have a hot center and cold edges...

People complain a lot about tires overheating but nobody bothers to post (or measure?) what temps the tire is at when it went off. For a heavy car like the Mustang there probably is no good solution short of actual race tires.

I'd love to come up with a datalog with at least 2 IR sensors aimed at each tire to read (admittedly surface) temps. Surely the wizards over at @SteedaTech and the GT4 guys have something.
 

Champracerj

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All,

As mentioned there are a lot of variables here, including alignment, camber, driving skills, track temps. on and on.
A simple thing I use to get started is to mark the side walls to edge of the tread in 3 places on each tire with a tire crayon. I start with pressures a little high and then drop the pressure as needed. That way you don't prematurely wear a new tire.
On the markings I look for how far I'm rolling to the edge of the tread (there are little arrow heads on the side walls as a max indicator). The Cold / Hot pressure that gets me to this edge is the pressure I use.
 
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Something interesting I found in the 2020 GT500 owners supplement. It suggests 38 psi F and 36 psi R on the base GT500 as well. The base comes with PS4S tires.
F108CB44-7403-44BF-BB0D-C6E0572F1A31.jpeg
 

Eritas

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IR guns are a waste of time. Get a probe or don't check at all.

34-36 hot is a good ballpark.
 

Tomster

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because PSI is not a reliable indicator. Get an IR gun, take the temps of the tire. Adjust air till the tire gets up to optimal temp. Adjust air to keep it from exceeding temp.

If you measure PSI, be sure to use the same gauge for consistency but your run of the mill is only accurate +/- 2% if you're lucky. Spend $200 and get a certified unit if you're going to play PSI games.

sidewall construction, camber settings, sensitivity of butt-o-meter, heat cycles on compound, age of tire all factor in. One man's "hot" temp is another guy's "cold" because the one driver puts far more load into the carcass.
IR guns are not reliable for checking tire temps. Get a pyrometer. The probe us a out 1/8" long and gets the true temp. The IR gun just measures surface temp.

To measure the tire temp, you have to pull in during a hot lap after the tires have a chance to get to temp. If you check them after your cooldown lap, the temps will not be accurate. You are looking for a spread of no more than 15 degrees from outside to inside. A thing more than that you should tweak alignment.
 

Tomster

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28 PSI is a good starting point. That is the pressure of a COLD tire that has not been driven.

You need to check with Michelin for the target hot pressure and temperature for your 4S tire. I track Cup2s so I dont have your data.

Have you considered your alignment settings? What settings do you plan to use? Which track?

I monitor the TPMS sensors when I'm tooling around a fast track where pressures and temps are critical. Smaller tracks that are less demanding on your tires probably dont need that kind of attention. I would check them every so often. When driving. Keep in mind TPMS sensors are not as accurate as a quality tire pressure gauge, so use it as a rough indication to monitor a ballpark figure.
 

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