I know the recommended Psi is 33. Im thinking about setting the front to 33 and the backs to 31.5. Anyone else experiment to see whats the best psi to get the best speed of the line?

 

for drag racing?

 

what does "best speed of line" mean? launching, top end speed, mileage...?

 

Unless you are in a dedicated track car or doing runs on a drag strip for fun, just inflate them to the recommended pressure. You aren't going to gain anything whatsoever from tinkering with a few PSI on a daily driver except uneven tire wear and bad fuel mileage. If you're launching on the drag strip reduce pressure in the rear to about 22 psi. But if you have crappy street tires with no grip, that would be something to address first.

 

I agree with BB, for drag strip use only, you want to set the fronts to their max pressure, usually about 44psi, and rears is a hit or miss deal. Initially go to 26, then drop 2psi per run until you get worse, then air back up 2psi and continue the day. However, the less tread you have on a street tire, the worst traction you will have. Unlike drag radials, a street tire NEEDS tread to hook up. A bald street tire is equivalent to driving on ice.

For a MPG estimate, you can run the recommended pressure, or you can adjust to your driving style. I run my fronts at 36psi and my rears at 32. I am getting a consistent 18mpg in city driving. I have tried running at 40psi in all 4 and while I got 19, the handling was terrible and not worth the extra 1 mpg. How much weight you have in the car, how hard you drive, whether you are city or a highway driver, all factors in to what psi your tires should have to give you the best mpg. There is no set number to run, its all a variable until you find YOUR personal setting based on where YOU live and how YOU drive.

 

What kind of tires do you have?

 

I would lower the pressure to buy a different car.

 

Michelin Premium A/s tires. Grip Pretty good.

 

And whats best Psi for driving fast on the street?

 

Basic, grand touring, all season tires. They give a comfortable ride, but if you think they grip pretty good, you obviously haven't experienced a high performance A/S tire, let alone a summer compound.

If speed off the line (ie launching) is what you're after, a tire upgrade would be far more beneficial than fiddling around with a couple psi.

I've had absolutely no traction issues getting off the line with either Bridgestone Potenza S04s or my current Michelin Pilot Super Sports.

The manufacturers recommended settings. You don't really have tires conducive to pushing the car on the street. The tires you have are designed to be long lasting and provide a nice, quiet, comfortable ride when you are driving on the highway with the cruise control set at 75, and for that, the manufacturers recommended settings would be best.

You have the wrong tires to be trying to get out of the hole quickly or to push your cars handling. Sorry, but it is what it is

 

For Auto-cross, people pump their tires over spec, evenly front to back, to reduce tire roll-over.

For the drag strip, you pump up the fronts and reduce the rears, to reduce rolling resistance in the front and increase grip in the rear.

For the street, you run exactly the pressure recommended by the manufacturer.... because street, safety, proper tire wear, common-sense, etc.

For everyday all-season tires, just don't, man. You've got the wrong trousers, Gromit.

Is this thread for real? It kind of feels like performance theater.

 

Nothing you do to your tires short of buying better (grippier and more expensive) tires is going to make you significantly faster from stoplight to stoplight. Not even one tenth. Slow down and save that for the track. You don't need some magical inflation scheme, you need better rubber to launch faster.

You'll get a couple dozen people giving advice to do this or that to get a little quicker on street launches. Which I reiterate that you should not be doing. However, no amount of tricks in the world will make a crappy tire grip which is where launch speed comes from. A car with a set of Michelin PSS or Toyo T1R will launch faster than one on a set of inferior tires every single time (all other factors being equal).