Tire pressure recommendations

[OurPTGT]

When you folks go to the track, what tire pressure are you running up front?
Thanks,
KB

[Mike-in-Orange]

I run right around 35psi up front, but lately have been putting 45 in the rears. Here's my thinking - take it as you wish: Street radials will "crown" if you put too much air in them, allowing only the center of the tire to contact the road. Underinflate them and they will actually go a bit concave at the center, essentially just running on the outer edges. If you've ever seen those tread wear indicator photos where they show how unevenly a tire wears if under- or overinflated you know what I mean. So basically, to get the largest contact patch (and presumably best traction) out of street tires I recommend the, um, well, recommended pressure.

My rationale for higher pressures in the rears is simply for lower rolling resistance - heck, you're just towing those tires behind you, it's not like they do anything other than keep the back bumper from rubbing on the street!

[steve smith]

chek in your door i think is 34lbs for the 4 tires

[SteelBlueGT]

Mine says 38 psi

[Mike-in-Orange]

Guys, he isn't asking "what's the recommended tire pressure for a PT", he's asking "what front tire pressure are we running at the track"!

[Cal Cruzer]

quote:Originally posted by Mike-in-Orange

I run right around 35psi up front, but lately have been putting 45 in the rears. Here's my thinking - take it as you wish: Street radials will "crown" if you put too much air in them, allowing only the center of the tire to contact the road. Underinflate them and they will actually go a bit concave at the center, essentially just running on the outer edges. If you've ever seen those tread wear indicator photos where they show how unevenly a tire wears if under- or overinflated you know what I mean. So basically, to get the largest contact patch (and presumably best traction) out of street tires I recommend the, um, well, recommended pressureMy rationale for higher pressures in the rears is simply for lower rolling resistance - heck, you're just towing those tires behind you, it's not like they do anything other than keep the back bumper from rubbing on the street!

Mike, have you experimented with lower pressure at the track in the fronts. I agree, pump up the rears. If you can reduce the contact pacth at all it is just that much less resistance, like running skinnies on the front of a RWD car. I would think that dropping the fronts down even more would result in better traction.

[Mike-in-Orange]

Cal, my best results have been when running the fronts at 35 - maximum contact patch seems to work best and I get consistant 14.8 runs.

[steve smith]

25lbs to the front

[JPMS GT]

Watch a dragster leap from the line. I think the slicks only have a few pounds in them,and they go convex in a nano-second. You could go to Costco and get a little nitrogen, say 15 lbs. And, I saw the guys with the Indy lights cars with what looked like motorcycle tires on to move about the pits. These would work great to hold up the back end for a quarter mile!

[crazyjoe]

quote:Originally posted by Mike-in-Orange

Cal, my best results have been when running the fronts at 35 - maximum contact patch seems to work best and I get consistant 14.8 runs.

Mike,

I think the argument is that you're NOT getting the maximum contact patch when you run the standard PSI. When you nail the gas, you get use of that contact patch for a split second, then the weight is transferred off of the front wheels, resulting in a reduced contact patch because of inertia (tires spinning causing the tire to balloon a little) and less weight on the front of your car than the 35PSI expects.

Lots of FWD dragsters run their cars at reduced PSI on the fronts and increased on the rear to get better times.