velocitygarage

Hey guys, I'm going to the dragstrip next week and was wondering what the optimal tire pressure I should run on my 265 PS2s? Any recommendations would be helpful.

Thanks Guys

Dominic

DFW01E55

I go with 25 - 26.

TKLEI14

A little OT, but what should the pressure be at for normal driving, the dealer gave me the car with like 34 pounds in the tires, but the door says it should have 46 in the rear and 41 in the front. (for a E63 btw)

chiromikey

i run 41 on the street and 30 at the track.

SLK55R

is that if they aren't drag radials you definitely do NOT want to reduce the tire pressure too much from normal. Maybe a few lbs lower at most.

I experienced this myself on pilot sport cups. I reduced the tire pressure to low and it messed up the tire big time.

TKLEI14

I agree with the people who posted above me, 25 pounds seems very low.

Also I'm suprised that you are supposed to have 46 psi on the tires.

chiromikey

on our cars, this is correct...and not only correct for street tires but for d/r's as well. with the heavy weight our cars have, too little pressure will distort contact patch and decrease traction.

enzom

I drive with 36 lbs normally, but at the strip, I lower the rears to 25 lbs. If they don't bite, I drop them to 22-23 lbs.

MRAMG1

WHY

I have run 275/40/17's as low as 18 PSI for an autocross, and at the drag strip. in NO way did it hurt the tire/rim/car. Please explain how it hurt the tire "Big time" I am really curious on this my friend. Although, I have NEVER liked Michelins period so I would not stand up for their consrtuction to begin with. But I would like a little more info here please.

Loosing air pressure allows the tire to flatten out, ie making MORE contact patch, hence BETTER traction. YES it will reduce your load capacity, but we are not talking about towing here. Just remeber to pump them back up on your ride home.

See yeah

Fast55

Fronts at 40+ psi, rears at 20-22 psi VS my street pressures of 38/36 = a drop of over .1 sec in 60 ft. times.

chiromikey

we're talking cold pressures right? do you know what the hot pressures are during (right after) your autocross? too low of a pressure does not flatten the tire out to increase contact patch, it causes the tire to cup which gets exacerbated by the weight of these cars.

and for those that profess very low pressures, we're not running old bias ply tires with a 70 series sidewall or even a tire that has a small enough or soft enough sidewall to wrinkle with the lowered pressure. so what's your reasoning for lowering pressures (besides the fact this was what your father used to do in the 60's )? i'm not pretending to know everything but i've tested my tire pressures on this car to know what works and there aren't many with the recall software that have run the 60ft times on street tires that i have.

SLK55R

Because on the way home I got two flat tires. Did I pump up the tires before I left? Absolutely. Was the damage already done? yes.

Both the rears went flat with damage to the sidewalls. So thats what I meant by hurt the tire BIG time.

MRAMG1

Hey SLK55R:

Thanks for the explanation. Although I have personaly done this with MANY different brands, I am still suprised that it happened to you. Sorry for the bad time my friend. I would have suggested a call to the manufacturer if these tires died from this low pressure, as I am sure you could have atleast received a free set.

BFG has replaced tires for me, even after raod racing on them, because of scalopping. That is cutting out of the sidewall.

Chiromikey:

I understand that you meant MODERN tires, heck I am not that old my friend. And I too was talking about MODERN tires that I have used at the drag strip. BFG, Goodyear, Hoosier to name a few. Your tire annalogy is slightly off my friend, IF your tire is properly supported by the proper rim width. You are correct that under SEVERE underinflation, the center of the tire would tend to push up, and the opoosite effect under HIGH pressure. However real world physics cut in hear and the tire, if mounted on the proper width rim, would in deed flatten out giving a LARGER contact patch, yes even with a VERY stiff sidewall. All that I ask, before the huge debate, is try it out for one pass. I am telling you that my stang, set up for raod racing, could cut 1.80 0-60 times, on street tires, running about 20 psi. Every 4-5 psi increase cost me about .1 secondds. Please try it, you will not be dispaointed my friend.

See yeah

oldgixxer

I make a baseline run with stock psi,then MAYBE drop down to 35psi in back.I will inflate fronts to 50psi once at the track.
After 70 trips down the dragstrip thus far,I find 35-40psi in the rear works best for my particular car

chiromikey

actually i have tried it...many times. this is how i know what works with my car. maybe i have something special. i'm not interested what works for mustangs and the set-up i used in my camaro doesn't work either. in my e55 i cut 1.71 60ft times on 19" street tires at 30-34psi. if you can beat that in an e55 i'll go through my tire psi tests again and we can compare notes.

velocitygarage

So I am getting mixed results here, for some people low 20 psi works, and for some 30-35 psi works. I guess I just got to go out there and try it for myself and see what works for me then.

chiromikey

that's the best answer so far.

MRAMG1

Right on my friend

See yeah

MRAMG1

Glda to hear that it works for you and that you have tried other ideas. Good luck.

See yeah