GT3 track tyre pressure
Discussion
Gradually decrease the pressure until you find one that works for you. Dropping straight to 2.1 may not create the desired efect. the handling will be dramitically effected. Personnally i don't like going that low, the car begins to move around too much.
Obviously the first few laps will make the pressures soar, so they must be adjusted accordingly. Try bringing them back to the road pressures, go out again and work down from there. Unless you have your own compressor it can be a pain putting air back in if you go too low.
Obviously the first few laps will make the pressures soar, so they must be adjusted accordingly. Try bringing them back to the road pressures, go out again and work down from there. Unless you have your own compressor it can be a pain putting air back in if you go too low.
Running the pressures high will cause the car to move around on the tyres. If you get over pressured front tyres the car understeers, rear tyres and it oversteers.
Start with 30 psi, do a couple of laps then come in & take out air to reduce back to 30 psi. Do the same after a couple more laps and so on until the tyres are nice and hot and the pressures are stable. Remember that if you then drive the car harder the pressure may creep up as you introduce more heat, then set you final pressure of probably 30-32psi.
When you go back onto the track after a break the pressures will have dropped and the car will feel a bit loose. Work some heat into the tyres and the pressure will increase back up to your "working" temperature.
The trick is to try and remain constant interms of how hard you work the tyres. If you potter round for a couple of laps, especially cooling the car down at the end of a session, then the pressure will drop a bit, that`s why we all do silly things behind a safety car to try and keep heat in the tyres. It`s also why there are often accidents straight after a safety car pulls in, particularly when the air temp is low.
Ultimately your pressures are dictated by the temperature accross the tyre. A cheap pyrometer, (a tyre thermometer), is a good investment between a group of friends. The difference between the inner and outer edge temperatures is controlled by the geometry settings, (particularly camber). The difference between the centre reading and edge readings is controlled by pressure. Too low and the pressure is too low, too high and the pressure is too high. In an ideal world the readings will be equal accross the tyre.
Bet you wish you`d never asked now !
Henry
Start with 30 psi, do a couple of laps then come in & take out air to reduce back to 30 psi. Do the same after a couple more laps and so on until the tyres are nice and hot and the pressures are stable. Remember that if you then drive the car harder the pressure may creep up as you introduce more heat, then set you final pressure of probably 30-32psi.
When you go back onto the track after a break the pressures will have dropped and the car will feel a bit loose. Work some heat into the tyres and the pressure will increase back up to your "working" temperature.
The trick is to try and remain constant interms of how hard you work the tyres. If you potter round for a couple of laps, especially cooling the car down at the end of a session, then the pressure will drop a bit, that`s why we all do silly things behind a safety car to try and keep heat in the tyres. It`s also why there are often accidents straight after a safety car pulls in, particularly when the air temp is low.
Ultimately your pressures are dictated by the temperature accross the tyre. A cheap pyrometer, (a tyre thermometer), is a good investment between a group of friends. The difference between the inner and outer edge temperatures is controlled by the geometry settings, (particularly camber). The difference between the centre reading and edge readings is controlled by pressure. Too low and the pressure is too low, too high and the pressure is too high. In an ideal world the readings will be equal accross the tyre.
Bet you wish you`d never asked now !
Henry
On clockwise tracks I start the session on cold tyres 1.75 bar passenger side 1.8 bar drivers side. After about 5 laps the tyres come up to 2.1 bar all round. Most of the time only a little bleed is required. An experienced driver can get the tyres up in 2 - 3 laps. If you start on under inflated cold tyres, they will warm quicker..
Steve R
Steve R
Steve, I was always under the impression that you were supposed to only let air out of the tyres to get them to the correct pressure, the reason being that starting off with lower pressures can cause damage to the sidewalls of the tyres. The theory makes sense to me, I appreciate you know far more than me about such matters, I just wondered what you thought on this??? Cheers.
Many thanks for these helpful replies, however as a Continental I am unfamiliar with PSI. How many bar does 31 or 32 PSI equate to roughly ?
Second, if the consensus is that the warm tyre pressure should be about 2.1 bar back and front, why does Porsche recommend a higher pressure for the rear than for the front for road use ?
Second, if the consensus is that the warm tyre pressure should be about 2.1 bar back and front, why does Porsche recommend a higher pressure for the rear than for the front for road use ?
Pirelli say that the tyre will work at 2 bar because it does not need air pressure to supplement the rigidity or something of the tyre.
I generally run the fronts lower than the back to give me a rear turning bias, from memory 32F 34R hot
cheers
C
PS when you get home and put the car in the garage you should blow them up again to 2.5 / 2.8 bar sorry about the mix of measures its just how i remember it.
I generally run the fronts lower than the back to give me a rear turning bias, from memory 32F 34R hot
cheers
C
PS when you get home and put the car in the garage you should blow them up again to 2.5 / 2.8 bar sorry about the mix of measures its just how i remember it.
clubsport said:
Steve, I was always under the impression that you were supposed to only let air out of the tyres to get them to the correct pressure, the reason being that starting off with lower pressures can cause damage to the sidewalls of the tyres. The theory makes sense to me, I appreciate you know far more than me about such matters, I just wondered what you thought on this??? Cheers.
clubsport,
Olaf Manthey insists on this, and his word is good enough for me.
flemke said:
Steve, I was always under the impression that you were supposed to only let air out of the tyres to get them to the correct pressure, the reason being that starting off with lower pressures can cause damage to the sidewalls of the tyres. The theory makes sense to me, I appreciate you know far more than me about such matters, I just wondered what you thought on this??? Cheers.
clubsport,
Olaf Manthey insists on this, and his word is good enough for me.
Thanks for the confimation, I certainly won't be changing my routine then...Cheers.
Thats interesting. When we are testing Parr send me out on under inflated tyres. They almost always get it spot on and only a little bleed is needed if any after about two laps. I have never had a tyre problem and it makes bringing the tyres in a lot easier. Generally after a few laps they come up and I can start to push on. I hate going out on cold tyres set at 2.1 bar, they baloon very quickly, need a lot of bleeding over several laps and tend to go off quite quickly.
If you get a chance to hang around in the pit garage before the start of a Carrera cup race you will find race engineers agonising at the cold start temperature of each tyre. All cars start with under inflated tyres because there is no time to bleed off during the race. It is even more critical for a sprint driver in the Porsche challenge because his tyres MUST come after a few corners.
I am intersted in the context in which Olaf made his comments and what they actually were. I have a lot of respect for him and Paul Robe. They both have a lot of experience in racing 911's at top level. It's interesting that they appear to have different views on this subject.
Steve R
If you get a chance to hang around in the pit garage before the start of a Carrera cup race you will find race engineers agonising at the cold start temperature of each tyre. All cars start with under inflated tyres because there is no time to bleed off during the race. It is even more critical for a sprint driver in the Porsche challenge because his tyres MUST come after a few corners.
I am intersted in the context in which Olaf made his comments and what they actually were. I have a lot of respect for him and Paul Robe. They both have a lot of experience in racing 911's at top level. It's interesting that they appear to have different views on this subject.
Steve R
The next time that I speak with OM I'll enquire further, but he seemed to leave no room for doubt.
The circumstances were that I was running a set of fairly new Cups that appeared to be in good nick. When, however, I took fairly high speed bends (such as Kesselchen and Mutt Kurve), an odd rumble would come from the rear wheels. This is not a sound that one welcomes at those particular bends.
After a mechanical investigation uncovered nothing out of the ordinary in the metal and plastic parts of the car, we concluded that the tyre carcases had been damaged. Olaf then talked about the right and wrong way to get tyres up to the correct pressures.
He is even opposed to letting a car stand for a few days without the pressures having been restored to their standard cold level.
The circumstances were that I was running a set of fairly new Cups that appeared to be in good nick. When, however, I took fairly high speed bends (such as Kesselchen and Mutt Kurve), an odd rumble would come from the rear wheels. This is not a sound that one welcomes at those particular bends.
After a mechanical investigation uncovered nothing out of the ordinary in the metal and plastic parts of the car, we concluded that the tyre carcases had been damaged. Olaf then talked about the right and wrong way to get tyres up to the correct pressures.
He is even opposed to letting a car stand for a few days without the pressures having been restored to their standard cold level.
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