Autocross Cold Tire Pressure

[ZeroGSR]

What is everyone running as their cold tire pressure for Auto-X on the stock tires? Was going to start around 38psi front, but wanted to see if folks are leaving the rears at stock pressure or bumping them up a bit as well, or going as high as 41 in the front like is recommended for high speed driving (which is still 33 rear).

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[Jester04]

What is everyone running as their cold tire pressure for Auto-X on the stock tires? Was going to start around 38psi front, but wanted to see if folks are leaving the rears at stock pressure or bumping them up a bit as well, or going as high as 41 in the front like is recommended for high speed driving (which is still 33 rear).

I usually start at 32-33psi cold for auto x. Once they heat up they get up in pressure pretty quick.

 

[sholzer]

38 cold for the front sounds like a good starting point. The PS4Ss don't have a very stiff sidewall and if you're pushing the car, you'll get some roll over onto the sidewalls. Rears can go either way to play with balance, some folks like to run lower pressures to get more rotation, but you can get the same effect running higher pressures, more preference and how the tires are wearing IMO.

 

[spectre186]

I just went with the factory pressure. Pretty new to autocross. How do raising and lowering pressures front and rear affect handling?

 

[optronix]

I just went with the factory pressure. Pretty new to autocross. How do raising and lowering pressures front and rear affect handling?

You may have noticed that after your first couple runs, the tire pressures climbed. Depending on the ambient temp and how sunny it is, this can change from day to day, event to event.

Tire pressures can have a pretty profound effect, although I have to concede that I haven't figured this out to an exact science yet. I'm not new to autocross, but I'm not a prolific veteran either.

One thing I have noticed though is these factory 19" Michelin PS4S are finicky. They absolutely will roll over, and roll over badly. This condition can be remedied by a few extra PSI of air pressure... but you have to be careful not to go too high or your car will then understeer badly.

Like I said I'm not the most seasoned autocrosser; I've only really gotten semi-serious in the past year or so. But I do like to think I push the car hard, and that's at least a little bit validated as I generally finish in the "upper 1/3" of times for the day- occasionally coming in around the top 10 mark- and my car is completely stock. My ego makes me actually walk around and check tires of who's faster than me, and I feel inadequate if they're on non-200 TW tires unless it's a Porsche or similar tier sports car.

So all that being said, the last time I was out I went with a bit higher than I normally would, starting out at 38 front and 35 rear. I had to back that off as the temps quickly shot up to ~41-42 in the front and the car pushed (e.g., understeered) really badly on certain sections of the course. Might have been just the course, might have been my shitty driving and getting on the throttle too much, but backing it off to ~35psi cold in the front seemed to help with that on this particular course.

Overall I think these cars are solid off the factory line but the tires are not ideal for autocross (I think they're actually better for light track/HPDE use than autocross- and not perfect for either), plus the car needs a little more camber. If you're serious, start thinking about that now- although if you are truly just starting out try to get at least a few more events in this season to at least get some money out of the PS4S and then you'll appreciate the 200 TW tires more when you do get them.

 

[menikmati]

I just went with the factory pressure. Pretty new to autocross. How do raising and lowering pressures front and rear affect handling?

IMO you will see more benefit in refining your driving line, corner entry/exit and backsiding/clipping cones during the slalom versus dialing in tire pressures.

 

[optronix]

IMO you will see more benefit in refining your driving line, corner entry/exit and backsiding/clipping cones during the slalom versus dialing in tire pressures.

You're not wrong- but seriously, if you're running the OEM tires, chalk them.

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