Why can't I ever be happy with my tire pressure settings?
 

I got a question about tire pressure guys. I have 205/50/15 BfGoodrich Gforce Sport tires on 15X5.5 12 lbs rims. I am running 36 cold front and 32 cold rear. The car feels very very nice when the tires and car are cold, but after awhile like 30 min to 2 hours the car feels kinda twitchy in a straight line. Also it feels like the car does not want to take corners as well. I have had this problem for quite sometime, making me always adjust the tire pressure. IM I OVER THINKING THIS WHOLE TIRE PRESSURE THING! I also notice when the outside temps are above 85 degrees, the problem is even worse. All my suspension has been changed except for my end links and rear trailing arm bushings.

If all of your suspension bits have been changed out, how recent was your last alignment, and how much faith do you put in the shop that did the alignment?

If the car feels "twitchy" in a straight line, and the tire pressures are anywhere *close* to correct, I'd be looking at things like toe-in/toe-out and other alignment settings before tire pressure.

I agree that an alignment is absolutely necessary after suspension mods.

I set my tire pressure at 35-36 all around and forget it. With mushy rear tires compared to the front, I'm sure the rear end does not swing around as well as it might if the pressure was a bit higher.

Well I had my alignment done like 2 months ago. The shop I went to specializes in only European cars. I been going there for a while and I do trust them greatly.

My Alignment:

Front toe: 1/16 toe out
Rear toe: 1/16 toe in
Front camber: -0.3 left -0.5 right
Rear camber: -1.4

Rear sway: 18mm HandR on stiff
Tire pressure: 36 front 33 rear

What you guys think?

toe out on the front???
why so much rear camber?
is that OEM spec? I've never looked into the factory numbers but most cars have a slight toe in on the front to aid in straight line stability.

Try some nitrogen or dry air to minimize pressure changes with respect to temp.

-my 0.02

i think it's the front 36 and hotter temps outside?

if you're going to motor in hotter temps (80F+) why don't you
start 2psi+ lower? that's wat i do in summer vs winter.

winter i use 36-38psi depending on temps.
summer i use 33.5-35 psi depending on temps.

basically the pressure goes up at least 4psi in the summer months
when you motor so your front tires might be over inflated for the
setting you want.

imho your alignment isn't bad. you might want to zero toe the front
and give slightly more toe-in on the rear if adjustable.

well guys I have a lot of suspension mods!

My mods:

Koni adjustable yellows
H-sport springs
Powerflex front control arm bushings
H-spot rear control arms
HandR 18mm rear sway
Future mod: OMP lower strut brace

My current settings:

Koni yellows: front- (all the way soft)
rear- (1 turn from soft)
HandR rear sway: (on soft)
Tire pressure: 36 (front) 32 (rear)

All the tires have good tread too!

SO.....

I finaly found the sweet spot in my car! I fooled around with settings more and this what I like.

Tire pressure: 35 front 34 rear
Koni yellows: front(1/2 turn from soft) rear(1 turn from soft)
18mm HandR rear sway: full soft

The car is so much more stable in a straight line and the car handles bettter too with more grip. Also the ride improved a lot with not it being so jittery feeling. Any thoughts?

my thought is that my post above was accurate.