I have been rebuilding my 86 Na 6 port engine for the last three weeks. I'm just about finished and the first Autocross race of the season is two weeks away!!!!!!!! Can someone tell me about the range of tire pressure I should start out with. I know it will vary given conditions at the race, but I don't want to show up completely unprepared. I've got 255x55x15 tires on 6.5"? wide aluminum wheels.

i'm pretty sure most autox guys run high tire pressure like 50psi! i am not 100% sure since i have never autox'd :(

Vosko, you're right, for street tires, most people raise up the pressure. I don't know about 50... I started at 40 and settled down to around 36 in the front, 34 in the back for my best runs. That was on a warm day with 205/40/17's. With my sidewalls so short, I didn't need to have the pressure jacked up too much.

run 40 initially...

use the chalk test to adjust thereafter..

Amp, I did the chalk thing too but what exactly am I looking for... just how much is wearing off up the sidewalls? Not much was wearing off at all so I was lowering pressure.... is that right?

255/55/15's on 6.5" wide rims? Are you serious or is that a typo? 205's are as wide as you want on a 6.5" rim.

if your noticing shoe polish or chalk off from your sidewall markings...

youll need to increase your tire pressure...

everytime i've auto crossed, I always start out at about 30psi then adjust after each run, as they heat up i drop it down to usally around 28 when they're hot



ps I'm running BFG euro T/A's 195-50-15

yeah my jaw dropped when I read that.

Yeah, Amps got it!

Start them out around 40, chalk it,

Drop it a few psi, until you notice chalk missing.

Yeah. . and about the 255, Yikes!

I'd be a little nervous about that, Unless those sidewalls are MEGA reinforced they're gonna role!

Alright, alright I got carried away with the "5" key. They are 205's sorry, sorry. But I do want to say thanks for the input guys.

40 rear, 42 in the front......



kumho victoracers......225/50 16 on the stock wheels....

We played a lot with tire pressure. We race two RX-7's in Autocross. A 87 TII with 260 HP and a 87 GXL with 150ish HP. We both started with street tires I had toyo poxes on the TII and the GXL had Azzenas (SP?) We both took a vets advice and we wre running 40 lbs for 3 to 4 events. We were always having traction issues. Another vet was talking to us and knew RX-7's well. He tols us to play with the pressure. He told us to start at 30 lbs and go from there.



I found my optimum setup on the TII with the Proxes. (255/40/17 rear 225/45/17 front)

Front - 30-34 lbs depending on the course and ambiant temp.

Rear - 28-30 lbs.



The GXL seemd to like about 1-2 lbs more front and rear.



We did both the shoe polish and pyrometer (surface temps) when we experimented.







We moved on the Victoracers on the TII and we added camber plates we run 2.5° of negative camber in the front and we have a camber link in the rear and run 2° of camber in the rear. We started with the same tire pressure as the Proxes we did this for a couple of events then got the wild idea to play with the pressure at a practice day.



We ended up running 28-30 front and 26-28 rear. The cars handling changed a lot by dropping that couple of punds out of the Victoracers. Pyro readings were telling us we were right on target with those pressures.



It sucks to have to play with this stuff at an event. Do you have a practice day the day befor the event?? I strongly suggest you go to it and try to sort this out.



I personally would start at 30 lbs. Then go from there. You might find 40 lbs will be better. Welcome to Autocrossing.