Optimal tire pressure
#16
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I e-mailed them back and asked if they could forward my question to the engineering dept. or their racing development dept. because I wanted a technical explanation and this is what they sent back...
Hello Mr. Reed,
As our technicians are out in the field at the dealerships, the best person to speak with in regards to this inquiry would be the Service Department at your local Porsche dealer. You can locate your dealer at www.porschedealer.com.
Should you need further assistance, please don't hesitate to contact us at 1-800 Porsche, Option 5.
Warm regards,
The Porsche Contact Center
1-800-PORSCHE
(1-800-767-7243)
So they send all of their engineers to the dealerships to just hang out? Wow...that's cool. Haha...
Hello Mr. Reed,
As our technicians are out in the field at the dealerships, the best person to speak with in regards to this inquiry would be the Service Department at your local Porsche dealer. You can locate your dealer at www.porschedealer.com.
Should you need further assistance, please don't hesitate to contact us at 1-800 Porsche, Option 5.
Warm regards,
The Porsche Contact Center
1-800-PORSCHE
(1-800-767-7243)
So they send all of their engineers to the dealerships to just hang out? Wow...that's cool. Haha...
#17
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So... how low is too low? I'm at 28F 36R right now. These are the N1 Michelin Pilot Sport Rib tires. I keep lowering the pressures and the centers are still higher than the avg of the outside and inside; although the insides are starting to get hotter (barely) than the centers on the rear. The fronts are 10-15 degrees hotter at the center than the inside & outside.
Is this maybe why Porsche went to 19" wheels? In order to get the sidewall stiffness and correct tire contact patch they went to a bigger wheel with a lower profile tire?
Is this maybe why Porsche went to 19" wheels? In order to get the sidewall stiffness and correct tire contact patch they went to a bigger wheel with a lower profile tire?
#18
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I e-mailed them back and asked if they could forward my question to the engineering dept. or their racing development dept. because I wanted a technical explanation and this is what they sent back...
Hello Mr. Reed,
As our technicians are out in the field at the dealerships, the best person to speak with in regards to this inquiry would be the Service Department at your local Porsche dealer. You can locate your dealer at www.porschedealer.com.
Should you need further assistance, please don't hesitate to contact us at 1-800 Porsche, Option 5.
Warm regards,
The Porsche Contact Center
1-800-PORSCHE
(1-800-767-7243)
So they send all of their engineers to the dealerships to just hang out? Wow...that's cool. Haha...
Hello Mr. Reed,
As our technicians are out in the field at the dealerships, the best person to speak with in regards to this inquiry would be the Service Department at your local Porsche dealer. You can locate your dealer at www.porschedealer.com.
Should you need further assistance, please don't hesitate to contact us at 1-800 Porsche, Option 5.
Warm regards,
The Porsche Contact Center
1-800-PORSCHE
(1-800-767-7243)
So they send all of their engineers to the dealerships to just hang out? Wow...that's cool. Haha...
#19
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So... how low is too low? I'm at 28F 36R right now. These are the N1 Michelin Pilot Sport Rib tires. I keep lowering the pressures and the centers are still higher than the avg of the outside and inside; although the insides are starting to get hotter (barely) than the centers on the rear. The fronts are 10-15 degrees hotter at the center than the inside & outside.
Is this maybe why Porsche went to 19" wheels? In order to get the sidewall stiffness and correct tire contact patch they went to a bigger wheel with a lower profile tire?
Is this maybe why Porsche went to 19" wheels? In order to get the sidewall stiffness and correct tire contact patch they went to a bigger wheel with a lower profile tire?
Porsche went to 19" wheels because they look cool. The cup cars still use 18 inch.
FWIW, I keep my tires at 34 front and 36 back cold.
#20
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Ok... since we are talking tire pressures. My local PCA (zone 1, NNJR) suggest 2-3lbs on top of factory recommendations on the track. WTF? After my adjustments, I was getting as high as 52psi at the end of the session... After much discussion with other people, there is a wide variations of what people use (on the same model cars)... the range is as low as -10psi and +3psi for the front and -6psi and +3 psi on the rear. With this much variations... Id say tire technology has come along way.
#21
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Ok... since we are talking tire pressures. My local PCA (zone 1, NNJR) suggest 2-3lbs on top of factory recommendations on the track. WTF? After my adjustments, I was getting as high as 52psi at the end of the session... After much discussion with other people, there is a wide variations of what people use (on the same model cars)... the range is as low as -10psi and +3psi for the front and -6psi and +3 psi on the rear. With this much variations... Id say tire technology has come along way.
Street tires are obviously different than race tires but for comparision, Hoosier engineers suggest somewhere around 36 to 38 hot. That means you have to start at around 28. For our Michelin slicks we start under 20 lbs cold and stay under 30 hot. 52 seems insane to me.
Do you know the logic behind the recommendation? Is it specifically for 996s or just DE cars in general?
#22
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What tires? That makes no sense to me. It actually sounds dangerous but they must have has a reason for those pressures.
Street tires are obviously different than race tires but for comparision, Hoosier engineers suggest somewhere around 36 to 38 hot. That means you have to start at around 28. For our Michelin slicks we start under 20 lbs cold and stay under 30 hot. 52 seems insane to me.
Do you know the logic behind the recommendation? Is it specifically for 996s or just DE cars in general?
Street tires are obviously different than race tires but for comparision, Hoosier engineers suggest somewhere around 36 to 38 hot. That means you have to start at around 28. For our Michelin slicks we start under 20 lbs cold and stay under 30 hot. 52 seems insane to me.
Do you know the logic behind the recommendation? Is it specifically for 996s or just DE cars in general?
I talked to one instructor and said that for street tires the temp on street tires rises slower.
one reason is that the flex on the tires is less on higher pressure.
If you lower your pressure the flex (eg: cornering) is greater and is a bigger concern (tire fatigue). To him +7 psi of recommended 36/44 wasnt a big deal, because they are cold pressure from the start... BTW our sessions are 20-25min, 2 in the morning and 2 in the afternoon.
#23
Race Director
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Several years ago I did an Audi DE at Louden in NH and they mandated 5lbs. over(cold) recommended tire pressure. They also checked your cold pressure during tech. inspection before you went on the track.I don't have an explanation as to why though.
#24
Burning Brakes
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I've instructed with Audi Club and they do tend to recommend a bit of overfill, but that's primarily because most of the drivers run 32psi all around. However, I don't think the same should be applied to a P-car; different tires, different weight distribution etc.
For new drivers in P-cars at DE days I recommend the factory settings until the driver starts getting fast, expecially in the turns. Then check hot pressures, equalize them side to side and keep them under 40psi.
For new drivers in P-cars at DE days I recommend the factory settings until the driver starts getting fast, expecially in the turns. Then check hot pressures, equalize them side to side and keep them under 40psi.
#25
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Using Michelin PS2 an an example in AX/DEs.
Has anyone tried driving AX or DE at high (>40#) and lower (34-38#) tire pressure. The higher tire pressure (>40#), from my experience, has a lower grip level leading to slower times.
Of course there are other variables not factored in, but in general I do not let my tires get above 38#.
Has anyone tried driving AX or DE at high (>40#) and lower (34-38#) tire pressure. The higher tire pressure (>40#), from my experience, has a lower grip level leading to slower times.
Of course there are other variables not factored in, but in general I do not let my tires get above 38#.
#26
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Using Michelin PS2 an an example in AX/DEs.
Has anyone tried driving AX or DE at high (>40#) and lower (34-38#) tire pressure. The higher tire pressure (>40#), from my experience, has a lower grip level leading to slower times.
Of course there are other variables not factored in, but in general I do not let my tires get above 38#.
Has anyone tried driving AX or DE at high (>40#) and lower (34-38#) tire pressure. The higher tire pressure (>40#), from my experience, has a lower grip level leading to slower times.
Of course there are other variables not factored in, but in general I do not let my tires get above 38#.
#27
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I've instructed with Audi Club and they do tend to recommend a bit of overfill, but that's primarily because most of the drivers run 32psi all around. However, I don't think the same should be applied to a P-car; different tires, different weight distribution etc.
For new drivers in P-cars at DE days I recommend the factory settings until the driver starts getting fast, expecially in the turns. Then check hot pressures, equalize them side to side and keep them under 40psi.
For new drivers in P-cars at DE days I recommend the factory settings until the driver starts getting fast, expecially in the turns. Then check hot pressures, equalize them side to side and keep them under 40psi.
I ran them under 40psi during DE and I agree they do feel better.... but either way, running them hi above cold temp or low hot temp doesnt make sense to me... It almost seems like tire pressures are just one of those trial and error thing till you find something that your comfortable with, a very personal choice.
#28
Burning Brakes
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ok... but Porsche recommend 36/44 cold. Running them at under 40 hot has more tire flex no? isnt this bad?
I ran them under 40psi during DE and I agree they do feel better.... but either way, running them hi above cold temp or low hot temp doesnt make sense to me... It almost seems like tire pressures are just one of those trial and error thing till you find something that your comfortable with, a very personal choice.
I ran them under 40psi during DE and I agree they do feel better.... but either way, running them hi above cold temp or low hot temp doesnt make sense to me... It almost seems like tire pressures are just one of those trial and error thing till you find something that your comfortable with, a very personal choice.
Anyway, a couple of things to keep in mind about adjusting tire pressure on the track
As you get faster your hot pressures increase, primarily because you generate larger slip angles in the turns, creating more friction = more heat = more pressure. As a general rule I like to keep hot pressure under the max tire pressure shown on the sidewall. On a hot day at the track if I'm driving hard, I can see an increase of 15 psi or more over cold pressure.
Second, tire pressure can be used to tune the handling. Lower pressure gives you more grip by increasing the size of the contact patch, so I run lower pressure up front to help reduce understeer.
Just my $0.02.
#29
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Using Michelin PS2 an an example in AX/DEs.
Has anyone tried driving AX or DE at high (>40#) and lower (34-38#) tire pressure. The higher tire pressure (>40#), from my experience, has a lower grip level leading to slower times.
Of course there are other variables not factored in, but in general I do not let my tires get above 38#.
Has anyone tried driving AX or DE at high (>40#) and lower (34-38#) tire pressure. The higher tire pressure (>40#), from my experience, has a lower grip level leading to slower times.
Of course there are other variables not factored in, but in general I do not let my tires get above 38#.
#30
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I agree with JimB on the pressures. 34 / 36 cold for a track day with PS2 (or lower) . After a couple of laps they can easily come up 5 - 10psi depending on the track. Once they get over 40psi hot it is like driving on ice they really lose grip ... I can't imagine overfilling, sounds dangerous to me .. lower psi is better
i have a stock 996, stock alignment, next track day I'm going put as much negative camber in as I can and see if that increases the grip level ..
i have a stock 996, stock alignment, next track day I'm going put as much negative camber in as I can and see if that increases the grip level ..