bigalnash

has anyone tried going from 35 psi all around to 40 all around to see if the car would handle better/worse?

Jared07gxp

I ran mine at 40 for a few days to see if it would help cornering and such, and the only real difference i noticed was alot more road noise and i could feel more of the road imperfections through the steering wheel. It didnt handle any better or worse.

vroom_vroom

iTrader: (5)

Mine are rated @51

bigalnash

well i did it anyway steering is much much lighter..

JC05GXP

What are you guys normally running, 35? I'm still at stock 30psi . Any wear issues running at 35?

LS1 Racing

iTrader: (15)

I always go sidewall pressure. Hurts ride quality a bit, as mentioned, and is a little noisy. But I've noticed better handling and improved MPG.

LS1>girlfriend

iTrader: (19)

You pump your tires up to the maximum sidewall pressure? If that's the case, enjoy excessive wear in the center of the tread and you have less of a contact patch.

LS1 Racing

iTrader: (15)

I was probably inflating my tires this way when you were still riding a Big Wheel.

Going with sidewall pressure is not the same as OVERINFLATION. If you've experienced these things, then I would venture to say that you don't keep your alignment within spec and/or don't rotate your tires.

We rotate RELIGIOUSLY every 5000 miles, and have never had uneven wear UNLESS the alignment was off.

gxp-miller-gxp

i would never put it at 40, i had it at 45 after autocross on highway and way home, and i felt as if i did not have much control.. like easy to wipe out in a sense. i would keep it at 30-35

4EVER3

I run mine at 40psi and tire wear is normal I also like the road fill

mikesss

I stay around 37psi. Feels great.

LS1>girlfriend

iTrader: (19)

Sounds like you've been over inflating your tires on your vehicles old man, recommended tire pressure for my GXP is 30PSI by GM. That pressure is to maximize contact patch determined by weight of the vehicle. Using a higher than recommended tire pressure will cause excessive wear in the center of the tire tread due to the tire "ballooning", over inflating also negatively effects handling since the higher the PSI in a tire, the bouncier it is, causing the tire to bounce more on uneven roads.

This is pretty common knowledge and I'm surprised an old timer like yourself doesn't know this.

EDIT: Inflating tires over manufacturer spec will cause excessive treadwear to the center of the tread, under inflation causes the outside of the tread to wear more than the center. This will occur even when the wheels are properly aligned and suspension components are in good condition.

CenTexSS

iTrader: (2)

Inflating per sidewall doesn't automatically = uneven wear. I have a lot of customers who run sidewall tire pressure and don't have much of an issue, even though I don't recommend it. I agree it can definitely cause wearing in the center of the tire, but doesn't mean it 100% will happen.

GXP25

iTrader: (3)

I thought it was 32 (sticker inside driver door jamb).

LS1>girlfriend

iTrader: (19)

That's because there is more force exerted on the center of the tread, decreasing your contact patch.

A few pounds over manufacturer spec doesn't increase wear very much, the higher over spec the tires are inflated the greater the wear with respect to manufacturer PSI specs. Using maximum tire pressure as listed on the sidewall can also be dangerous, since people usually check tire pressure when the vehicle is parked chances are the tires are cold. So max cold tire pressure can mean an addition 5 PSI when warm or hot which could cause a blowout, since the general rule is 1 PSI for every 10*F the tires heat or cool.

Just checked my door again and it says 30 PSI cold, front and rear.

LS1 Racing

iTrader: (15)

Results are what matter to me, not the anecdotes of some dude on the internet.

This practice has served me well for a long time. I've never had a blow out, nor have I experienced abnormal treadwear, and I typically outperform the EPA on MPG. You can choose to believe this or not, I don't really care.

I will air-down when going to the track, and for obvious reasons.

LS1>girlfriend

iTrader: (19)

I too only care about results, that's why I use correct tire inflation practices.

Excessive treadwear of over inflated tires won't be noticeable to the average driver until at least 10k and higher mileage of consistent over inflation. If you over inflate like you say you do, measure the tread depth in the center of the tire and then compare that to either outer edge (assuming you drive like you should on the street). There will be a difference, more on driven wheels, less on free wheels.

Why do you air-down street tires when you're at the track...greater contact patch. There's really no other reason unless you have very soft sidewall street tires.

Nice job trying to belittle me, it's difficult to teach and/or learn things when people either think they know everything or offer personal attacks. In this case it's both, but I'll tuff through it and offer what I've learned anyway

Here a few visual aid to help understand.


And a few articles
http://www.popularmechanics.com/cars/news/4199963
http://www.dunloptires.com/care/proper_inflation.html
http://www.ehow.com/list_6109527_eff...ion-tires.html

vroom_vroom

iTrader: (5)

Your tires last that long I usually end up burning through a set a year ( it's hot out and I like to burn em)

rkvette

i agree with ls1> girlfriend post ! tire mfg. and vehicle factories spend a lot of time/monies to come up, with best normal tire air pressures. of course you can always go up/down , for your personal opinions .. i have always found mfg. numbers are best !! rkvette

Panther427

So lets see here... yes yes and no no...... the factory psi rating was technically devolped for the tires that came on it from the factory.. Now yes GM, i'm sure thought of other tires will be use on this car lets get a good all around preasure to use.. However there are SEVERAL things that you should take into consideration.... The number one most important thing in my book is weight,,,,,, AS in how much extra weight do you normally carry around. IF its just you in the car at all times that great run it at factory spec.. But i have noticed most of the tires at least in the GXP's have higher than normal max preausres vs 55-65 series tires. 45 to 50psi max is fairly common. And with thin side walls its good to have some extra psi to equallize the force..
I also run at least 2 more psi than the door sticker. but that puts me at 32psi for my TPMS and most gauges are reading like 36psi...

Every tire is different so once tire at 40 will be great, your next set wont handle for crap at 40 or 30 but like to be at 34.. So yes the door jam sticker is a starting point... but we are on here to modify our cars.. what easier than tire air preasure.

I like having extra couple psi in my tires because i never know when ill be caring extra weight and slight improvement in gas milage.

And as for airing down street tires. I have been trying different psi at the track.. i find a few psi lost has worked for me so far...even with our short side walls it seems to still allow a bit for contact patch and sidewall flex. though still experimenting... Then again when i air down its generally from a higher preasure to begin with