LFA951

I am currently running 40 psi on all four tires, I have Hankook Ventus RS2 Z212 all around with a maximum of 51 psi. What pressure do you all use for street applications?

RKD in OKC

36psi all round

ausgeflippt951

36 is what factory said, but that's def low as far as I'm concerned.

For street I always take max pressure (mine are 44) and subtract ~3. I noticed the better gas mileage immediately (meaning, the next tank).

333pg333

Probably depends on the tyre and the aspect ratio / sidewall stiffness v's comfort level too?

Driftomagnifico

Tire pressure is a function of suspension setup, tire downforce moment, and the tire construction.

That being said, you should read up on taking tire temperatures if you are tracking the car. Otherwise just keep air in them.

RKD in OKC

The max pressure rating on tires is for the full load rating. You will always get better gas mileage with higher pressures, but that does not mean you are getting either max grip or wear.

The old skool rule of thumb is measure the tires cold, then drive highway speeds and thru some fast turns then measure them immediately while hot. They should gain 10% in pressure. If they don't gain 10% pressure you have too much pressure in them, if they gain more than 10% you don't have enough pressure in them. Modern radial street tires take about 3psi to make any difference in how they handle. You also need a very accurate tire gauge for this method. Mine is a 3 inch dial 60# Accugauge.

Another method is to measure the tempuratures across the tire tread after running them enough to heat up the tires. The center of the tire should not be hotter or colder than the outside edges. Hotter equals too much pressure, colder is not enough.

Suspensions are designed to use the tires pressures as part of the spring and shock system. Correct tire pressures make a big difference in handling. As an example my 2005 BMW 325i recently got new tires. The tire shop put too much air in them. The car drove very smooth, but squirly like the tires were almost flat. After bringing the pressure back down to the factory recommended pressures it drove much much better.

A cold tire pressure of 40# is usually recommended to novice autocross drivers as they tend to spin out and slide sideways a lot. The increased pressure not only lets this happen a lower speeds so they can learn control, but helps to keep the tires from rolling off the rims while going sideways.

Driftomagnifico

If you do the tire temp measurement method you have to account for suspension geometry.

RKD in OKC

The temp method works if your suspension is not set up correctly and either the inside edge or outside edge gets hotter. You just try to keep the middle of the tire pressure between the two outside edge pressures. We are talking street tires and assuming not having a radical suspension setup.

LFA951

I read in Tirerack that their rule of thumb is to subtract 1 psi for every 10 degrees of temperature minus the max psi for the tire for heat expansion. For example, if my tire takes 51 psi max and it is 90 degrees, I should put in 42 psi...

LFA951

That was 20 years ago when tires had a maximum of 44 psi, the book is outdated, tires nowadays are far superior

Rip It

I just had new tires installed, asked the same question. Taking into consideration the advances in tires over the last 20 years I would have thought the factory suggested tire pressure would be outdated. Not the case.....for street use the tire pressure should be set to the factory suggested amount.

RKD in OKC

My 2001 Boxster S called for 36 all round. It handled best with 34 all round. That pressure was derived from both the gain method and the temps across the tire hot. When Hot the pressure increased to 39.5 psi.

My 2006 BMW X3 came with 19in wheels with Pirelli Rossos on it. It calls for 32 front and 34 rear.

I don't think modern tire design is for higher pressures even if tire rack recommends it.

ausgeflippt951

Yah correct. FWIW, MY tires are 44 max! haha I've found that my car handles best at 41 (they're bridgestone turanza all-seasons...bleh...came w/ the car).

It's different for each car, but I've never had a flat w/ the "minus 3 rule" and on every car (except for the true high-perf ones) I've found an improvement in handling and mileage.

Then again, I really like stiff-sidewall tires so there you go. Oh and BTW my wear has been fine for mine at 41 psi.


It's different for each tire; experimentation is the only way you're gonna find out what is best for your setup.

Jake951

I've found that at the factory recommended pressure (36 psi all around), the rear tires wear much more in the center than the edges. This is for the Turbo S stock tire size (245/45/16) on stock rims (9x16). Anyone else see the same behavior?

LFA951

I feel mine fine at 40 psi