Hey guys.

Is anyone else running street tires for HPDE events? If so, what tire pressures are you running F/R?

I don't have money for an extra set of wheels and R-comps right now, so I'm trying to make the most out of my street setup. I don't do parking lot auto-x, so I'm not interested in 40+psi setups that I've seen a lot of those guys run.

Tires are Nitto NT555, 255/45/18 Front, 285/40/18 rear.

For the track, I run 33psi in the front, and 23psi in the rears. This puts the wear pattern right on the "triangle" wear indicators in the shoulder blocks, F and R.

What kind of pressures is everyone running, for a benchmark? I've heard that getting the tire pressures optimized is the quickest and cheapest way to shave some time off of laps.

 

19 Views and no knowledgable replies? :-/

 

I seem to hook better running a little higher pressure than 23 in the rears. I got less wheel spin running 30 in the rear tires than I did running low 20's, but I don't do any road course racing. just a little drag racing for fun.

I have the exact same tires as you btw and same stagger.

 

I would suggest 42 lbs. in the front and 32 lbs. in the rear. This compensates for the built in understeer. Then front tires lose traction before the rear, causing an oversteer condition that is helpful in turns on a road course. With 32 lbs all the way around, the car just wont turn. Also I have never had the rears roll over the rims with only 32 lbs of air in the rears. I have had the fronts roll over on 38 lbs. of air. My $.02.

 

I took a instructional road course session last year and was told to run the tire pressure that was noted on the tire.

 

Any other input from our usual RR suspects? (ImportSlaya,Fastduo)?

 

A tire guy at the track ( road race ) told me to run 5lbs. less than the max inflation on the side of the tire when the tires are up to track temperature.

 

275x40/18 Nitto 555 on 9.5" front/back.

After six Hot Lap track days, I like the Front @ 32 psi Rear @ 28 psi. (Cold)

 

That's the same tire/wheel combination I run. I'll try the 32 front 28 rear cold thing on my next track day. I think I well be changing to either Toyo R888 or Hoosier R1's for next seasons track day. The street 555's aren't the best trackday tires.

 

They stick great when they get hot.
After the third lap you can start pushing.
They don't make noise, to warn you, when they are going to give up.
18k miles with at least three more track days.
Rotate . . .
People think I have R tires.

 

I don't have any experience with 18's, but given the stagger I would start with the rears at 3-5 psi less than the front (cold pressures) and adjust from there. 35 front/30 rear is probably a reasonable starting point. Sounds like you may even drop psi based on coolmac's experience, but Reverend went higher (was this for autocross, though?), so it's tough to say.

How much negative camber are you running up front? That can make a big difference, too. If you can run -2 to -2.5, you shouldn't have to go to more than 35 psi up front.

 

OK thanks for the advice! To be honest, I'm not sure how much camber is up front. I can see the negative camber slant in the front wheels, but it's not a ridiculous amount. Probably -2.0 tops, or whatever the spec on the FRPP pack says. The dealer did the alignment when I had the FR3 kit installed at delivery.

 

I think the FRPP pack uses the the Eibach Prokit springs. When I installed mine, my camber was at -1.5 if I remember correctly. About as much as you want to run for a daily driver, but if you are doing a lot of track events and AX you will want to run another degree or so of negative.

 

I run 275-35-18 all the way around and I start out cold at 36 front 33 rears. I always adjust right before going out on coarse. My tires will usually come up an average of 5 psi front and rear.
When I run slicks I run 34/31 psi.

 

Good info, good info

 

Good to know. Do you (or anyone else) have some recommended pressures for the Nitto 555RII (basically the same as the Toyo Proxes RA1) in 275/40/17? I've never run a tire with this stiff a sidewall before and want to get some basic starting points.

P.S. Is that Homestead or Sebring? Great picture.

 

For 17's, I will run the same pressures. It has always worked well for me.

That picture is Homestead Miami Speedway.

These are is Sebring....

 

A couple more from Sebring....

 

Ended up going with 40 front/32 rear. We'll see how this goes on race day. If I don't like the pressure in the fronts, I still have the ability to release some pressure. Car certainly feels more solid during turns above 25mph on the street.

Track is Firebird East, btw. Usually we drive Phoenix International, in the Grand-Am setup.

PS Sweet pics fastduo

 

Ditto!