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    cgt tire pressure?

    what is everyone running? the 32/32 in the book? if so, i just took mine down from 38/38 - never checked it when i got it (i know - VERY bad). anyway, the car feels a bit looser with the 32/32 than the 38/38 and i would have expected just the opposite. any experiences with this are appreciated. tia

    Re: cgt tire pressure?

    I wish mine is here, I would've told you about my experience . But anyway, does the book recommends a max/min pressure?? If not I suggest you keep it @ 32 and drive it for a while.

    Re: cgt tire pressure?

    ben, the Porsche recommended tire pressure is always the MINIMUM tire pressure. I would take the recommended tire pressure for a fully loaded car and add around 0.1 bar to it. This should do just fine. On the track, go with the lowest recommended tire pressure and make sure you warm up the tires first during the first two rounds.

    Re: cgt tire pressure?

    Quote:
    RC said:
    ben, the Porsche recommended tire pressure is always the MINIMUM tire pressure. I would take the recommended tire pressure for a fully loaded car and add around 0.1 bar to it. This should do just fine. On the track, go with the lowest recommended tire pressure and make sure you warm up the tires first during the first two rounds.



    thanks. that is exactly what i was looking for.

    Re: cgt tire pressure?

    Ben,

    How are you measuring the pressure?

    Did you use the Tire Pressure Monitor (RDK) built in to the car, or did you use an external guage?

    The RDK system has air-temperature compensation built into the readings. Very cool.

    Re: cgt tire pressure?

    Did you guys see the Excellence article on the GT2,3 and CGT in the April issue? They have a picture of their loaner CGT's gauges and the pressures were 30f/29r.

    Greg A

    Re: cgt tire pressure?

    Quote:
    W8MM said:
    Ben,

    How are you measuring the pressure?

    Did you use the Tire Pressure Monitor (RDK) built in to the car, or did you use an external guage?

    The RDK system has air-temperature compensation built into the readings. Very cool.



    Mike - Is the air temp measured the ambient air temp or the temp inside the tire? Would be interesting if it were the latter

    Re: cgt tire pressure?

    Quote:
    W8MM said:
    Ben,

    How are you measuring the pressure?

    Did you use the Tire Pressure Monitor (RDK) built in to the car, or did you use an external guage?

    The RDK system has air-temperature compensation built into the readings. Very cool.



    I use an external gauge to check/fill (as the manual also advices) though I use the RDK system to monitor how much they inflate as they are driven to see if the addition is too high or ok. FWIW, I set them at 32/32 today and experienced 8 to 10 PSI increases when putting the car through it's paces. For that kind of driving, I think I'm going to move up 2 PSI (from 32) at a time to see if I can achieve more like a 5 to 6 PSI increase.

    Re: cgt tire pressure?

    Quote:
    ben, lj said:
    I use an external gauge to check/fill (as the manual also advices) though I use the RDK system to monitor how much they inflate as they are driven to see if the addition is too high or ok. FWIW, I set them at 32/32 today and experienced 8 to 10 PSI increases when putting the car through it's paces. For that kind of driving, I think I'm going to move up 2 PSI (from 32) at a time to see if I can achieve more like a 5 to 6 PSI increase.




    Raising the "cold" PSI should not affect the "hot" delta. W/ dry air or N2 it should follow the PV=nRT law. The deltas you are getting sound reasonable.

    Checking the proper tire pressure is the 1st thing I do when I buy a new car, right on the lot. BTW... PAG ships all their cars w/ tires inflated well above their recommended PSI - the dealer should have adjusted that, but clearly not.

    Also... make sure you use an accurate gauge - one of the digital gauges made by ACCUTIRE, which are very accurate +-0.5PSI. The fancy, brass, analog gauges are nice but go out of adjustment easily.

    Re: cgt tire pressure?

    Quote:
    Grant said:
    Mike - Is the air temp measured the ambient air temp or the temp inside the tire? Would be interesting if it were the latter



    I believe it's the tires' internal air temperature that's used to make the judgement as to whether pressure is within nornal operating parameters.

    Re: cgt tire pressure?

    Quote:
    ADias said:
    Quote:
    ben, lj said:
    I use an external gauge to check/fill (as the manual also advices) though I use the RDK system to monitor how much they inflate as they are driven to see if the addition is too high or ok. FWIW, I set them at 32/32 today and experienced 8 to 10 PSI increases when putting the car through it's paces. For that kind of driving, I think I'm going to move up 2 PSI (from 32) at a time to see if I can achieve more like a 5 to 6 PSI increase.




    Raising the "cold" PSI should not affect the "hot" delta. W/ dry air or N2 it should follow the PV=nRT law. The deltas you are getting sound reasonable.





    really? i always thought they got much hotter when underinflated? btw, i would think the CGT with slicks would be absolutely INSANELY fast on the track. the tires are most def the weakest link.

    Re: cgt tire pressure?

    Quote:
    ben, lj said:
    Quote:
    ADias said:
    Quote:
    ben, lj said:
    I use an external gauge to check/fill (as the manual also advices) though I use the RDK system to monitor how much they inflate as they are driven to see if the addition is too high or ok. FWIW, I set them at 32/32 today and experienced 8 to 10 PSI increases when putting the car through it's paces. For that kind of driving, I think I'm going to move up 2 PSI (from 32) at a time to see if I can achieve more like a 5 to 6 PSI increase.




    Raising the "cold" PSI should not affect the "hot" delta. W/ dry air or N2 it should follow the PV=nRT law. The deltas you are getting sound reasonable.





    really? i always thought they got much hotter when underinflated? btw, i would think the CGT with slicks would be absolutely INSANELY fast on the track. the tires are most def the weakest link.




    If they are grossly underinflated, yes they will heat faster, but that is a different mechanism. However if yo say the ballpark number is in the low 30s, I think that the +DIFF should be about the same if you start at 30 or 32.

    Re: cgt tire pressure?

    Quote:
    ADias said:
    If they are grossly underinflated, yes they will heat faster, but that is a different mechanism.



    Correct! AFAIK!

    Gross underinflation adds extra heat due to excessive side-wall flexing. Tire carcass design, tread compound heat range, and vertical load all contribute to the final temperature rise due to slip induced heating. Out-of-spec, excess side-wall flexing just adds to it.

    Re: cgt tire pressure?

    I don't know is this applies to sportcars but in sportbikes, when you use stiff carcass-soft compound tires, you lower tire pressures a couple of PSI's so that they heat up faster (cold tires on a car is OK but in a sportbike it can take a whole other meaning ) and also achieve the higher operation temperature that they need to grip under colder weather.

    I'm using DOT racing tires on my sportbike, so its a problem to get them to their high operating temperature on the street, forget about riding in wet, so pressures are ussually lowered, specially on winter days on these types. Since they have a very had carcass they can withstand lower pressures than normal tires for which factory pressures are designed for, just like R-compound Pilot Cups on a car.

     
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