tire pressures for autocross setup

[Stretch]

Today, I started running with 45 PSI in the front and 34.5 PSI in the rear. It was ok- a little tail-happy in the first run. Once the tires warmed up, I measured 50PSI front and 38PSI rear. It made the car extremely tail-happy... I think we'll see some pictures soon of me flying through the course sideways, wiping out cones. That was crazy fun, but going sideways is NOT fast! Actually, it was rather uncontrollable.

Still, any less that 45PSI in the stock front tires, and you'll be going on your sidewalls. I had major wear there last time running 40-45PSI.

On my final run today, I needed a drastic change so I lowered it all the way to 43PSI front and 38PSI rear, and I no longer had much tail movement. I felt very smooth at that tire pressure, but I could've been a little faster. In some of the U-turns, I couldn't quite get the tail around as much as I hoped. So, 43 was too low- barely.

So, I think the best autocross tire pressure I've found for a 6i is about 45PSI front, 38PSI rear.

Your mileage may vary. Crossbow, Ashu, Necessity? How'd it feel?

[tireswap]

Its much easier to control oversteer than it is understeer... although you cant really throttle overteer in a FWD car :)

[crossbow]

Necessity actually lowered his pressure and reported better grip.

There is such a thing as too much pressure stretch.

I'm quite happy with 40 in the fronts and 32 in the rear.

I might try 40/40 next time for fun :).

Now if I could just avoid turning on the blinker, lights, wipers, wiper fluid, and horn...I'd probably get better times.

[Doc Roadster]

QUOTE

Originally posted by crossbow

Now if I could just avoid turning on the blinker, lights, wipers, wiper fluid, and horn...I'd probably get better times.[/b]

:D I don't know. I've seen some pretty fast times cross the stop line with wipers going.

[ashutoshsm]

QUOTE

Originally posted by Stretch


So, I think the best autocross tire pressure I've found for a 6i is about 45PSI front, 38PSI rear.

Your mileage may vary. *Crossbow, Ashu, Necessity? *How'd it feel?[/b]

I dunno - I used 43-ish fronts, 36-ish rears. I felt good about those pressures. Eric was comfortable as well - and actually said I shouldn't change it because it felt suprisingly neutral. He drove my car for 3 runs, and I did (hold your breath) 7 runs as well! However, I didn't think to measure the pressures when hot - no clue how that would help! I did inspect the sidewalls for riding, and didn't see any indications that they were. Although all the tire wear from today happened at/around the edges.

Bear in mind I have the wonderful 16" H-rated Miche-craps! And I see missing chunks (or shredding, at least!) on parts both my fronts! Yay! I can justify new tires by summer if I wear these out quickly ;)

Now, if only I can control my urge to give it more gas and apply abrupt braking/steering - basically, get it all going smoother - I think I might even be able to get better times, further justifying an 'investment' in nicer tires ;)

[ashutoshsm]

QUOTE

Originally posted by crossbow
There is such a thing as too much pressure stretch.[/b]

Why would pressure stretch? Wouldn't it ... press?

QUOTE

Now if I could just avoid turning on the blinker, lights, wipers, wiper fluid, and horn...I'd probably get better times.[/b]

Hmm - sure. But then whom would we rib and tease on the tarmac?

BTW - we know you were just showboating because you knew the camera was trained on you. Spotlight-hog!

[Stretch]

It still looks like I'm on my sidewalls in the pictures, even at 50PSI. Also, I could feel the outer part of my tires still being the warmer part after each run.

I guess there's no helping it.

[Necessity]

They were at about 44 hot in the front. Seemed to hold just fine. My tail stuck as well at 33.

[chrishart1]

QUOTE

Originally posted by Stretch


* * * * * * It still looks like I'm on my sidewalls in the pictures, even at 50PSI. *[/b]

Unavoidable with the stock camber settings, I would imagine.

[crossbow]

I'm going to try a higher pressure in the rear next time. Makes the tail happier :).