Tire pressure? (spirited drive)

[biketsai]

Im going on a drive tomorrow and was wondering what would be tthe best to set my pressure at. Its going to be a very fast drive while going around corners around 60-80mph. I am running 225/40/18 tires with a max pressure of 50 psi.
Currently the tires are set with the Front at 42 and teh rear at 38.
thanks

[sixfiveoh]

Should be more in the rear to counter the understeer. Be careful, dude.

[Seerlah]

The more psi, the better gas mileage yet lesser handle (fast corners). The less psi, the more the car will grip to the road. The max on my tires currently is 45psi and I have them all set at 40. But I don't go speeding into corners.

[gmx]

50psi?

I think you're going to have a crap contact patch and a very worn middle section of the tyre.

The only advantage of that level of psi is less heat buildup.

[InTTruder]

50 rear is dangerous, especially cold. 80/90 "corners": I know you're not street-racing: 80/90 on a street corner would get my attention and I'd call the polizei. SO let's assume you only think you're that fast. ANd yes, I am a rocket scientist,and I track. SO I know what your car can really do. All your hardware will not permit a street corner at 90!
Not to be so serious, but let's keep it real here folks.


I track and autocross my TTQC and Avant. Typical cold is 42f/38r on the TTQC (225/40x18 Nitto Invo), and 42f/40r on the Avant. I adjust after each run: look at the wear on the edge of the tread blocks and +/- as necessary.

Seerlah has it wrong: fewer psi does NOT equal better grip. It can be adjusted up or down to manage your oversteer/understeer tendencies, but it has little to do with better grip. Sorry dude.

[ricebeater]

Can you guys read? He said he is currently running 42f/38r for his tire pressure not 50. I would say those are good numbers, thats usually what I run and my max is also 50.

[biketsai]

I had iit set at 42/38R and it ran great! No understeer although I came in hot into some corners.

[djwimbo]

to counter the understeer.

You mean you still have understeer? Between the H-Sports and 4:1 Diff mod, it's pretty darn balanced. I haven't hit the track yet, but AutoX and messing around on the streets it's a world of a difference.

back on topic though.
I'd probably drop the pressure down to 38psi Fr and 36psi Rr. The 42/38 would be good for the street, but if you're trackin it or AutoX I'd go a bit lower.

I ran my all seasons in AutoX @ 44psi all around, but that's a 205/55R16. I didn't have an option really.

[ExpLlclT]

35 up front 40 rear

[ExpLlclT]

also to counter understeer trail brake into corners

[D's Avant]

On my Avant (225.50.16) I run 38 psi front and rear. Works well for me and stock sport set-up and my moderately aggressive street driving.

[Oricle]

I'm running 32-33 psi on 215/55/16.

[Jibberific]

I have all four of my tires at 38 psi and it's working out great

[Oricle]

I have all four of my tires at 38 psi and it's working out great

Maybe I'll try cranking mine up to 38 PSI.
Have you ever ran lower?

[MattzWarsteiner]

Sounds like a fun day OP!

Seerlahs right on in loose sand or snow. Lower psis do get you more traction, but on pavement wet or dry, more pressure is mo better.

Learned about sand psis when my motorhead cuz & I were on a beach somewhere we didnt belong in his previously unstoppable 4x4 and got ! haha stuck. Local dude has us nearly deflate all 4 and drives right out of the sand after we got the beast up off its axles & frame.

[Jibberific]

Yeah, but much lower than that and I start to get some "tire squishing during corners" action going on. I like my tires to be more solid during cornering and hold their shape. Plus it's more protection against potholes and stuff.

[InTTruder]

Be specific: what do you run, and what are the results.

The only succesful inflate is one where the maximum contact patch is maintained through the turn. Too high and you narrow the "circle of friction". Too low, and you have a large but squishy/squirmy mess that will not stay on the rim. Worse, soft fronts promote understeer, and soft rears promote oversteer.

See the following link for best advice on handling and getting out of the apex.
West Texas SCCA tips

Play it safe: use the right pressure, not too much or too little. If you really want to know, get some soft chalk and mark your tread block in 3 places around the tire perimeter. If you aren't going to the edge, you're too high on pressure. If you go onto the sidewall, you're too low.

Pay attention, do it right, and "quit guessing". The 6 y/o chasing that ball who isn't expecting your 90+ street dash is going to panic. Will you?

[andyrew]

To do it right, take tire temps.

Inside Middle Outside... If the middle (Looking at it like (__) where "(" is inside, "___" is middle, and ")" is outside) is higher, lower your pressure, if its lower, raise your pressure. If inside or (most likely) outside is higher, you'll need to do some math.

Another idea is to take chalk and make some marks 1" in from the edge of the tread to the tread and 1" onto the sidewall, if your using all of your tire, (not rolling over to the sidewall) then your pressures are probably fine.

GL