Air Pressure Changes Steering Bias?

[TundraOnKings]

Seems dangerous.

My Lexus on 555G2’s (arrow) and my S550 on GY SC3’s…..
I lived

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[Shadow277]

? What do you mean? Lol

To run them that low. Won't they run off the beads?

 

[Ewheels]

To run them that low. Won't they run off the beads?

If you don't have camber, you'll go a whole lot lower on the sidewall than those markers.
You'll be fine, stop worrying. Aim for 38psi hot, get some camber eventually, and you're good to go

 

[luc]

I don’t think I’ve ever seen it mentioned online, and I had no idea, nor did my track buddy that’s been tracking his 911 for 13 years. Until my last instructor showed me.

So he showed me a neat little trick on my GoodYear SuperCar3’s….there is a GoodYear “wing” emblem, on the side of the tire. For track, you adjust your pressure on each tire until you’re scrubbing the tip of the wing.
So I checked Michelin’s - same deal, there is a marker, but it’s a little “balloon man”.

This seems so very simple to me, and last track day after adjusting the first session I was spot on, and the car felt amazing.

Not sure if this is just common sense that everyone knows, but it sure seems like it’s a really good starting/reference point for anyone adjusting pressure for track.

My instructor said tire MFG will also put an “arrow”, I just googled it, and this looks like he was correct.

Your instructor is both right and wrong
Yes, tires do have a reference mark that you don’t want to go over but tire pressure is not the only reason why you would go over or not
The other main and even more importantly factor is camber
Let’s say that you don’t have enough negative camber in front and the tire is rolling over the symbol, jacking up the tire pressure to solve this issue is not only the wrong way to correct the issue but could also increase understeer by reducing front traction

 

[Shadow277]

If you don't have camber, you'll go a whole lot lower on the sidewall than those markers.
You'll be fine, stop worrying. Aim for 38psi hot, get some camber eventually, and you're good to go

My next track day is hopefully next month or December. I'll try it then.

 

[Shadow277]

Your instructor is both right and wrong
Yes, tires do have a reference mark that you don’t want to go over but tire pressure is not the only reason why you would go over or not
The other main and even more importantly factor is camber
Let’s say that you don’t have enough negative camber in front and the tire is rolling over the symbol, jacking up the tire pressure to solve this issue is not only the wrong way to correct the issue but could also increase understeer by reducing front traction

Thank you for taking the time to explain. It makes more sense now.

I'm pretty much stock and plan to stay that way. So use 38psi on stock suspension?
My only difference is that my springs are cut about 1.5 inches.

 

[NightmareMoon]

In my experience, 38PSI is the upper limit for hot pressures, above that grip falls off quickly. 36-37 when hot would be better. Adjust your cold pressures so you stay at or below 38 when heated up on track.

 

[GJarrett]

In my experience, 38PSI is the upper limit for hot pressures, above that grip falls off quickly. 36-37 when hot would be better. Adjust your cold pressures so you stay at or below 38 when heated up on track.

+1. I would rate myself a "novice-intermediate" driver with something like 15 days experience gained on 5 different tracks at this point in time. I run the Firehawk Indy 500 tires in 274/40r18 and found if I start the day at the normal 32 psi cold they will heat up to 37-38 degrees and seem to like it there. At that hot pressure they are predictable and perform well. One day by the last session which was 25 minutes, I noticed they got really squirrelly toward the end of the session. I checked the pressure after the cool down lap and they were at 40 psi.

IMO if you air up to 42 psi like your club suggests, you may end up feeling like you are running on an ice track after a few spirited laps.

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