AutoX Tire Pressure?

[AutoEuphoria]

What pressures have you guys found to work with the stock tires/wheels? I was thinking 45/42, but that is a complete guess LOL

 

[H3br3w_Ham3r]

wayyyyyyy to much. I ran like 25-30 in the fronts and 35 in the rear. You want more air in your rear tires to help eliminate the understeer and help the car rotate.

 

[AutoEuphoria]

Ah, OK Thanks for the advice!

 

[joe149]

Repeating another post I just did, but I just autocrossed my stock MS3 with OEM Bridgestones, etc. I used 42/37 and it worked fine - no rollover, and no excessive understeer even on some pretty sharp and long corners. Turn the traction and stability both off.
Joe
p.s. car was great - driver sucked!

 

[funksilver07]

wayyyyyyy to much. I ran like 25-30 in the fronts and 35 in the rear. You want more air in your rear tires to help eliminate the understeer and help the car rotate.

25-30??? That seems a bit low for a street tire but if it works for you...just ran this weekend at 38psi all the way around, I'm using a set of 225/45/18 Dunlop Direzza sport Z1 star specs on stock rims. You'll have to experiment to see what works.(drive)

 

[slprrex]

40r/37f hot is what I ran on the stocks

 

[H3br3w_Ham3r]

25-30??? That seems a bit low for a street tire but if it works for you...just ran this weekend at 38psi all the way around, I'm using a set of 225/45/18 Dunlop Direzza sport Z1 star specs on stock rims. You'll have to experiment to see what works.(drive)

Well you are right the tires are not exactly street tires I run on and I was running low PSI that day to get more grip in the rain. Ran 32F/38R today in the dry after I noticed how much they were rolling over. Idk I just feel I get loads of grip with a low psi in the front

 

[funksilver07]

Hey it's all about having some fun. I love trying to dial my car in to squeeze another .05-1 second out of a run. Nice to see other MS3 owners out racing with their cars. I've found that no tire is the same and you have to just pay attention to how they're reacting to the driving conditions/car/and driver. Tire pressure does affect traction.

 

[Nliiitend1]

It's simple.

Take tire chalk and an IR thermometer to the event with you. Mark your tires/sidewalls so that you can see how much/little rollover you're getting, and use the thermometer to measure temps on the inboard/outboard tire tread areas between runs.

Use the gathered information along with how the car feels to make informed tire pressure decisions.

 

[Mr_Boom]

I've been playing around with the pressures on mine (just completed 5th AutoX) and have found that 36F / 38R works pretty well. But this is with BFG R1's as opposed to the stock Bridgestones.

 

[bacarl]

wayyyyyyy to much. I ran like 25-30 in the fronts and 35 in the rear. You want more air in your rear tires to help eliminate the understeer and help the car rotate.

Dude, if you weren't even running stock tires (like OP asked about) and were running in rain, why on earth would you make a post like this??

"OMG you're so wrong, but wait a minute my results were in totally different conditions than yours!!!!"

This is why forum posts must be taken with ginormous grains of salt...

If you run 25psi up front on the Bridgestone's, they'll roll excessively and you'll lose a lot of grip. It's more effective to increase pressures above what you'd run on the street to resist the loads which are higher than what's seen on the street.

It makes the most sense to "test n tune" like Nliiitend said. If sidewall chalk wears off, or if the temps are significantly higher on the outside edge of the tire, this indicates it may be rolling, so increase pressure by a pound or two to resist that tendancy.

I've come across two schools of thought wrt rear pressures/understeer. One states that higher rear pressures decrease grip by shrinking the contact patch, which allows more rotation. The other states that lower rear pressures increase tire roll and slip angle, which allows more rotation. I'm too dumb to know which is technically correct, but I have had better luck with lower pressures in the rear. I run around 41F/38R but it depends on the surface and how my runs feel.

Euphoria, when/where will you be autocrossing? I attend most/all of the events in/around Detroit -- do you venture that far south? I'm headed to Toledo with a couple boosted Miatas on the 28th for an SCCA event at an airport down there. (cool)

 

[H3br3w_Ham3r]

Dude, if you weren't even running stock tires (like OP asked about) and were running in rain, why on earth would you make a post like this??

"OMG you're so wrong, but wait a minute my results were in totally different conditions than yours!!!!"

This is why forum posts must be taken with ginormous grains of salt...

If you run 25psi up front on the Bridgestone's, they'll roll excessively and you'll lose a lot of grip. It's more effective to increase pressures above what you'd run on the street to resist the loads which are higher than what's seen on the street.

It makes the most sense to "test n tune" like Nliiitend said. If sidewall chalk wears off, or if the temps are significantly higher on the outside edge of the tire, this indicates it may be rolling, so increase pressure by a pound or two to resist that tendancy.

I've come across two schools of thought wrt rear pressures/understeer. One states that higher rear pressures decrease grip by shrinking the contact patch, which allows more rotation. The other states that lower rear pressures increase tire roll and slip angle, which allows more rotation. I'm too dumb to know which is technically correct, but I have had better luck with lower pressures in the rear. I run around 41F/38R but it depends on the surface and how my runs feel.

Euphoria, when/where will you be autocrossing? I attend most/all of the events in/around Detroit -- do you venture that far south? I'm headed to Toledo with a couple boosted Miatas on the 28th for an SCCA event at an airport down there. (cool)

I said this cause I have run 25-30 in the fronts before with the stock tires. A lot of roll yes but I don't care about the life of the sidewalls stock tires as I was just waiting to upgrade to something better. I did run better times with the low pressure but the end result wasn't too good for the tires.

The lack of pressure lets the tires roll and absorb the energy instead of sliding across the pavement like it would if inflated to a higher psi, which we all understand to be understeer. That is my logic which I have tested on my own and seen ok results. At least im not running 70psi like the guy who was next to me driving his carolla. He couldn't figure out why his car was understeering so bad (braindead.