david greenberg

Running Toyo Proxy RA1s, 225 fronts, 245 rears on 16" wheels on a 1989 TurboS. Can I get some suggestions for tire pressures.

TIA
David Greenberg
Fort Myers, Florida

slim_boy_fat

well the book states 36psi front 46psi rear

I run 36psi front 40psi rear

jimbo1111

Running that type of pressure the tires will surely over heat. I suggest starting at 26 front 29 rear. Warm them up for 3 to 4 laps and then take a reading. They should stabilize around 33 front 36 rear when warmed up. The track temp has a lot to do with it. If you get very aggressive on the track you may build up pressures over 45 lb and over heat the tires. This is dangerous because an over heated tire will have no grip. Monitor the pressure every few laps till you get it right. I run nitrogen in my tires. Much more stable then air.

Mike1982

Where do you get nitrogen from? Does the nitrogen help anything else then just keeping the temp about the same as you set it? I have thought about this to just compare the difference in normal air.

ed devinney

My local Toyo supplier and the PCA gurus here in the DC area advise ~40 psi hot, front or rear. For me that ends up being in the upper 20s to start (lower in front), as Jimbo says based on track temps. IMO 33/36 hot is too low for the RA1, but I'm not an expert.

slim_boy_fat

Sorry didnt realise it was for track driving.

ON track i would go 28F 32R cant bring myself to run them any lower than that.

Asarus

With street tires, you should try to get about 36 psi hot. So you have to adapt the cold pression according to the temperature, to your driving style, to the road surface, etc... make some tests to see what you need and if the car handles as you want

Sam Lin

Nitrogen reduces the pressure difference with temperature, mainly because it's totally dry gas. It's also better for your tires, there's nothing in it (unlike with atmospheric air) that will oxidize and age rubber.

Sam

jerome951

Assuming you have fairly stock suspension and alignment, you'll get significant outer shoulder wear (and severly reduced tire life) at front pressures below ~38. Make sure your sidewalls aren't rolling over too much.

I shoot for 42 psi hot front and 40 psi hot rear. Get a couple pounds over that, though, and they'll start to get greasy. For me, that means starting out at 35 cold front and 34 cold rear (on a normal day). This experience comes from running RA1s on the track for 4 years, though I use 235x17 front and 255x17 rear.

david greenberg

Jerome951,

You are the first poster to mention running higher pressure in the fronts. About five years ago I owned a 1988 951S but I can't remember the pressures I was running. When we raced spec Miata we would put more pressure in the fronts. Any particular rationale for this on the 951? I am running the stock suspension but with a lot of negative camber for the track.

sayporsha

For track days I run 36 front & 31 rear (cold). Set & forget. 1 pound higher in the rear & I start getting oversteer. 1 pound lower in the front & they will rollover on the sidewalls.

The car is completely neutral & it sticks like stink accelerating through the apex. This is on 17" Potenza S02's, 205/50 front & 255/40 rear. I'm going to try some R compound tires on 16" phone dials next season, so I will have to experiment to find the best pressure combo there.

Cyrus951

245/45/17 front- 29
255/40/17 rear- 32

Sam, where is nitrogen available?
Don't the new GTOs come with nitrogen filled tires from the factory?

jerome951

I have to run slightly higher in the front to manage sidewall rollover, especially when trailbraking. I get a little better stick at 38-40 psi, but get too much rollover and greatly wear off the outside shoulder. Car is very neutral at that pressure differential front:rear.

This is running stock TurboS suspension w/ -2.0 camber in front and -2.5 in rear.

You'll just have to experiment with slight changes in pressure to see what works for your car and driving style. Everyone is a little different, as you've already seen by the recommendations.