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sailsmen
10-02-2003, 08:58 AM
Does anyone know which tire pressure we should use.

I read where people were having the center of the rears wear and dropped the rears to 28psi.

Then I read the factory '04 went up to 35psi because the side walls are weak and cause the tires to wear at speed on the center.

Then I read the factory '04 went up for CAFE reasons.

There must be someone with some technical knowledge on our particular tires. Has anyone tried contacting BFG?

cyclone03
10-02-2003, 09:03 AM
35psi is for mileage (cafe) only.
I run 30-32 in front 28-30 rear.18000 miles fronts are still over 50% tread.Rears about 30% left,too many burn outs..

RF Overlord
10-02-2003, 09:48 AM
^^^what cyclone said^^^

I don't understand how "weak sidewalls" can cause the centres of the tread to wear... :confused:

While having a slow leak repaired at my favourite tire shop, the tech checked my tread with a depth gauge and measured 6mm in the centre and 8 mm on the outsides. I HAD been running 32 in the rear, so I've dropped it to 28...we'll see if the wear evens out.

sailsmen
10-02-2003, 12:29 PM
Supposedly the lower PSI allows squishing of the sidewalls which lifts up the tread at the outer edge.

looking97233
10-02-2003, 04:47 PM
From BF Goodrich's website:

General Rules For Adjusting Balance Using Inflation Pressures If you want more grip at one end of the car, raise the inflation pressure at that end. If you are already as high as you feel you should go at that end, lower the pressure at the other end. By changing the differential in pressures front-to-rear, you can dramatically change the handling of the car. If the car pushes (or understeers), raise the front pressures, or lower the rear ones. If the car is loose (or oversteers), raise the rear pressures, or lower the front ones.

Proceed cautiously. We recommend making changes of a couple psi at a time, and only at one end of the car at a time. We also don't recommend going below 20 psi, or over 44 psi. That is a very wide range to play in. If you are going to drive on the street, adjust your pressures to the vehicle manufacturer's recommendations.

In the event that you aren't able to find a recommendation for your car, or the tires on your car are so different from those that were originally fitted from the manufacturer as to be incomparable, use the following formulas:

(Vehicle weight in lb./100) + 2 psi at heavier end + 2 psi all around if suspension and alignment are stock

Example:
Stock 911, 3,000 lb.
(3,000/100) = 30 psi
Add 2 psi all around = 32 psi
Add 2 psi to heavy end = 34 psi at rear
With modified suspension, the result is 30 psi front, 32 psi rear

Also:

To get even tire wear when using DOT-approved tires, you must be very careful not to use too low a tire pressure. Probably the biggest adjustment you can make to improve tire wear is in your driving. Avoid sliding the tires or locking up the wheels under braking, and drive as smoothly as possible.