I put a band of chalk across the profile of the tire and some of the tread as well and went on a drive. The pictures below show the left over chalk. The first two pictures are of the front tire and the remaining are of the rear tire. I want to know how to interpret it correctly. It looks to me that most if not all the flat surface was consumed. This is good! What about the curved bit of tire - can I lower the pressures a mite to consume some of this area or is it dangerous to do so? Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login
You are optimizing your tire tread (I'm not sure that's what you really want, though). You don't want to make a tread adjustment on these cars via low tire pressure. That wear pattern hints that you don't have the factory negative camber dialed in. Set up like Ferrari intends, 348's wear the inside of the tread rather fast in normal street driving (but can carve high G turns). If you want to adjust tread wear from economy over to performance, then please do so via camber, castor, and toe-in rather than under-inflation. Just my thoughts. Your mileage may vary. The world is a diverse place.
Actually I was trying to find the right tire inflation through trial and error. The pressures on the door jamb/manual are way too high - it is very bouncy. Even at f/r @ 32/33psi the car is a bit bouncy. I was trying f/r 31.5/32psi when I took this pictures. The ride is a bit better.
The first thing you must do is make sure you are checking pressure with an accurate tire guage (which you may be doing already). Gas station guages are typically abused and I would not trust them. Pencil type guages don't have the accuracy or repeatability I would want. Are different pressures listed for different loading? A car full of passengers and luggage would typically need a bit higher pressure and of course the reverse is true. You really need a tire pyrometer if you want to make serious adjustments for best wear pattern or best handling (the two usually do not go hand-in-hand). Could the car be bouncy because something else has been changed like springs?
Do not lower pressures further IF you will drive agressively. The harder you drive, the more of the outer tread you will use...if you lower too much, and driving very hard, you could start using the sidewall.
I am using one of those digital pressure gauges. No idea about its accuracy. The car is usually driven with one passenger and about 20 lbs of cargo up front. That's what I thought too but I wanted to double check. I used it pretty aggressively and still didnt start using the sidewall. So I guess the pressures are OK. I am taking it to the track next weekend and will bump pressures by about 2psi all around and keep checking with the chalk to make sure I dont use the sidewall.
You will want to use 2 gauges for consistency. Digitals are neat, but lack accuracy, esp. if you drop them a few times (ask me how I know this); a high quality pencil gauge can work fine (not the $2 Wal-Mart one). At the track, your best friend for optimizing tire preasures is the pyrometer. Do a session and immediately after pyro the tire width to see if you have a hot spot. You generally want the entire tread to have a consistent temp. Higher in the tire center means overfill; lower means add preasure. Work fast and scan each tire before anything else (or have your abled bodied crew do it).
