goodyar eagle ntc5 195/55R16 on my new '05 MINI Cooper, runflats. Manual says 30PSI up to 100MPH and 4 adults w/luggage...then 35PSI for over 100MPH.
Sticker on my door lists my tire size and only says 35PSI.
Hmmmm.
What say ye, normal driving, solo, maybe an occasional passenger.
30, or 35 ???
gregc

 

33 is a great starting place!

Alex

 

Alex,

What about the old formula for calculating tire pressure based on the max tire load vs max. air pressure then calculating for the weight on each wheel?

Total vehicle weight: 3,500 lbs
F/R weight bias: 61%/39%
Maximum weight per tire: 1202 lbs @ 51 psi

.61 x 3500 = 2135 lbs front .39 x 3500 = 1365 lbs rear

Weight per wheel; 2135/2 = 1067.5 lbs per tire front 1365/2 = 682.5 lbs per tire rear

1202/51 : 1067.5/? = 45psi front 1202/51 : 682.5/? = 29psi rear

What are your feelings about this?

 

I would like to know how it applies
Alex

 

The applicatiion would be that tire manufacturers know more about their tire than the car manufacturers do. gregc was asking about air pressures for the MC after being confused by the owners manual and labeling on the car.

From racing I know that the formula stated gives a very good starting point for tire pressures. Fine tuning for conditions or driving habits. It seems to work for me to get even tread wear and tread life. The handling does not seem to be an issue either, not on the street or at an auto-X event. Heck, it even works with the low pressure electronics of the MINI.

Since the rear tires have so much less weight on them I have always found that rear tires of front FWD cars require less pressure to achieve even tread wear across the width of the tire. I monitor my tread wear and adjust the air pressure to achieve even wear, along with regular tire rotation. Too high a pressure results in faster tread wear in the center of the trie tread, too low a pressure accelerates the wear on both the shoulders.