Tire Pressure, HELP Please: 330 GT 2+2 Series II

Ferrari Message Board Archive 10/00-8/02
Locked
wwwboard
Posts: 0
Joined: Sun Oct 26, 2008 2:56 pm

Tire Pressure, HELP Please: 330 GT 2+2 Series II

Post by wwwboard »

Posted by Jack Horner

Help please.  Our car, number 8325, has Borrani wire wheels, 15 x 7 1/2,  and Michelin XWX 205 x 15 tires with tubes.  What is normal street tire pressure, front and rear?  

Any recommendations for what pressure to use for a Ferrari Club of America track day?

Thank-you,  Jack Horner &nbsp
wwwboard
Posts: 0
Joined: Sun Oct 26, 2008 2:56 pm

Re: Tire Pressure, HELP Please: 330 GT 2+2 Series II

Post by wwwboard »

Posted by Tom

Hi Jack,

When I used to take my Porsche on track events, I always ran a few pounds less pressure on the track. 32 Lbs for street, and about 28 Lbs for on the track. Check pressures as the tires heat up on the track. Another thing you could do is to chalk the tires to see if you're running enough pressure. Take some chalk, and mark the area on the shoulder of the sidewall where it meets the tread. After a track run, check to see how much chalk still remains on the tire. You want just enough chalk to be removed that covers the tread portion of the tire. If too much chalk is removed, increase your pressure.

Increasing and decreasing pressure front to back will also affect over and understeer, but you're only out to have fun, right?

Tom

P.S. When's the track event at Lime Rock? Maybe I'll come out to watch! &nbsp
wwwboard
Posts: 0
Joined: Sun Oct 26, 2008 2:56 pm

Re: Tire Pressure, HELP Please: 330 GT 2+2 Series II

Post by wwwboard »

Posted by Jack Horner

Tom, thanks.  I wrote the wrong wheel size, should be 7L (not 7 1/2) x 15.  Anyway the manual says 32 / 35 front / rear.  Seems really high.  Event is this Fri & Sat.  Jack
wwwboard
Posts: 0
Joined: Sun Oct 26, 2008 2:56 pm

Re: Tire Pressure, HELP Please: 330 GT 2+2 Series II

Post by wwwboard »

Posted by Jack Horner

Tom, thanks.  I wrote the wrong wheel size, should be 7L (not 7 1/2) x 15.  Anyway the manual says 32 / 35 front / rear.  Seems really high.  Event is this Fri & Sat.  Jack
wwwboard
Posts: 0
Joined: Sun Oct 26, 2008 2:56 pm

Re: Tire Pressure, HELP Please: 330 GT 2+2 Series II

Post by wwwboard »

Posted by Jack Horner

Spoke w/ Nick Soprano at Motor Classic and Comp in White Plains, NY.  Nick races in the Ferrari Historic Challenge and sold me this car.  He said street should be 28F / 30R unless the car speaks to you differently.  For a track event, not strictly racing, start with 32F / 35R.  If anything he said I might have to increase the front a bit if the car is understeering.  Jack  &nbsp
wwwboard
Posts: 0
Joined: Sun Oct 26, 2008 2:56 pm

Re: Tire Pressure, HELP Please: 330 GT 2+2 Series II

Post by wwwboard »

Posted by Tom

Hi Jack,

I don't think anything is written in stone, hence the "speaks to you differently" comment from Nick. Whatever works, works. Chalking the tires gives you a good idea what the tires are doing.

Tom
wwwboard
Posts: 0
Joined: Sun Oct 26, 2008 2:56 pm

Re: Tire Pressure, HELP Please: 330 GT 2+2 Series II

Post by wwwboard »

Posted by Pete

I suggest you start with slightly higher pressures and work down until either:

a. Tom's chalk method gives you the required indication, or

b. The car starts to squirm around too much.

Ultimately you should be measuring the tire temp, which is difficult to do, even if you have a suitable temperature gauge ... as the tires will cool off as you drive into the pits, etc.

The reason I say this is if you start too low (note: I am talking 2 psi variances here not huge amounts) you may over heat your tyres and wear them really fast and also the car may handle funny and move around too much, and give you strife.

I remember playing with tire pressures a long time ago (as my tire guy suggested that I might get the car to do what I wanted by lowering the rear pressures ... thus causing throttle off oversteer to get her to turn in better) and the change was dramatic, and I only lowered them by 2 psi ... and I nearly lost the car on a fast right hander over a hill. Thus be careful and as Tom said you are not in to win races anyway, are you :)

Enjoy yourself.

Jealous Pete
Locked