The rating on my A6 for tire pressure gives me stats for a smaller tire than I have on my car. Does anyone have any equations, suggestions? I've heard if you divide yout cars weight by 100 then that should be the PSI you should run. But, wouldn't different size tires require different psi? If the recomended psi for a 215 r 16 tire is 36 and I have a 225 r16 would I run it a little lower? Please feel free to flame me on this question.

 

Not very scientific but, I just look on the tire for the MAX PSI and set it about 5-10 lighter depending on season and if its my car or truck. Just my 2 cents

 

More likely than not you have the wrong tires on your car. Generally speaking the tires pressures dont change that much between tire sizes on the same vehicle. 36 will be fine for the size tire you have on your car.

 

Just remember this....(these are just examples)
Tire pressure (stated on tire) = 32 PSI
Summer = fill to 29 or 30 because the air in the tire combined with the outside temperature will expand to 32 and be perfect
Winter = fill to 35 or so depending on the temp (usually below 32 deg.) because the air is colder and is more dense.
Basically with this in mind follow the recommendations on the tire.
Racing = a whole other ball of wax. Going up a tire size doesnt change the fact that the recommended tire pressure still needs to be reached. Go off the tire and you have no worries.

 

30 psi all round unladen 36/38 rear with gear ( read the hand book )

 

unless your loaded with a caravan and 3 fat ladies then double it lolj/k

 

Thats definatly not what you want to do. The tire manufacturer only recommend the maximum tire pressure, which in almost every case is way to high for the vehicle. Use the pressure that is on the vehicle. The tire pressure on the vehicle is a cold tire pressure. Meaning car should have been drivin a short a distance as possible before checking pressure. The pressure you should set the tires to is the same no matter the ambient temp, however you will have to add air in the winter as the temp cools due to the fact that air will contract as it gets cold and presure will decrease. In summer you will have to remove some air due to expansion. Its aproximatly 2psi for every 10 degrees f.

 

u put whatever they say when the tires are cold...