wombat

First off, this is for 2007 vehicles...

Yesturday I was checking my tires PSI, and they were at 32...as recommended by the door sticker...However after getting into a little arguement with my girlfriends dad, we decided to solve it the civil way....We called the maker of the tires.

Now the arguement between him and I was that he thought my tires were WAY too low. The max PSI on the stock 2007 ss/sc tires is 50psi...I've got mine at the recommended 32psi. After calling the company, they said that the 32psi is only a recomendation that GM sets to get the most comfortable ride...However, in retrospec it KILLS your handleing (as the pirelli guys says)..So today (after I get my tint) I'm going to go to the gas station and pump my tires to about 45psi (that's what the guy on the phone recomended)...I'll tell you guys how it goes, and how it affects handleing...

Main reason I posted this was to see what you guys think about it...

Try not to flame, and keep it clean. Opinions?

hatrickstu

iTrader: (1)

dude of course the less PSI you have the softer the ride is, but it also wears the tires more evenly, you are going to way less tread in the middle than on the sides in just a few thousand at 45 psi

D4u2s0t

not necesarily true. on my 2.2, i kept it to between 40 and 45 psi all the time. original tires lasted over 32,000 miles, and still had plenty of tread when i sold the car.

alleycat58

Bad idea. These tires shouldn't be run that high over a long period of time. If you auto-x or road race, bump up the tire pressure and return it to "stock" when you're done.

The recommendation from GM isn't JUST for "comfort" it's also taking into account the load rating of the tire and how much weight it has to support on average.

Overinflating tires is just as bad as underinflating tires. The BEST indication is to look at how the tires are wearing when you rotate them. If they show even wear across the tire, they're at the proper inflation. If the middle of the tire is worn more than the edges, you're over inflating and if the edges are worn more than the center, you're underinflating.

45psi is rediculously high for a daily driver. I would not go above 35psi long-term. Hell even when I'm racing I don't EVER inflate the tires past 42psi or so. Keep in mind as well that as you drive, the tire will warm up and air will expand, raising the psi in the tire. You're only leaving yourself 5psi wiggle room, and that's not a lot and you leave yourself open to the possibility of having a blowout.

hatrickstu

iTrader: (1)

im at 50,000 miles on this balt now, ive monitored it haha

wombat

I've been testing my PSI...I would drive like 15-20 min on my tires, test the PSI before, and after...The most I've seen it flux is 2psi. Hell, once i saw it DROP 2psi...So I guess I'll leave the psi alone for now.

joeworkstoohard

indeed. on the 2.4 is recommended is 35 psi, and i'm pretty good at keeping it there. sometimes if i go on a long trip, i 'll add one or two for the extra mpg, but i've never had an issue with the car feeling soft in the tires. (stock p6 tires)

now, as she said, in an auto-x track or something, that's different, but for street driving, if you're going so hard that your tires are needeing more pressure, slow the **** down, man.

"The life you save, may be mine"

James Dean

lewisb13

Overinflated tires wear the centers, underinflated wears the outsides.

hatrickstu

iTrader: (1)

do i hear an echo?

DrPuttsSS/SC

Some of the auto-X guys pump theirs up into the 40s for events.
It can make the car more responsive by making the tire stiffer and giving it a smaller contact patch. It will also ride harsher and you'll get better gas mileage because of less rolling resistance.
But I bet going that far over recommended pressure will really wear your tires. Just going a few pounds over will wear the centers way faster than the outside of the tread. I'd bet you could wear them out with as little as 5K miles.
On a heavier car, you can get away with more pressure but on a Cobalt, I don't know.

just my 2 cents, your reality may differ

lewisb13

No you arent hearing an echo, read what you wrote. You said that at 45psi (which is overinflation) you have LESS wear on the center of the tire, this is INCORRECT. You arent going to use "way less tread in the middle" you are going to use wayyyy more.

alleycat58

No he said it correctly...

L.P.

Also keep in mind if you take long highway trips the psi will go up naturally in the tires due to expanding of the air molecules...therefore if you pump up the air pressure from 32 to 45psi while driving for a good disatnce it could go over that 50psi which would be very unsafe...just my .02

lewisb13

Sorry misreading it....read it quickly...looks like "you are going to USE way less tread...."

DrPuttsSS/SC

Another thing I just thought of, I wonder if that much pressure will heat the tire unevenly? If it is riding on the center strip I wonder if the center will heat up more than the rest of the tread, and whether that might have an effect on the tire construction?
Racing teams use pyrometers to ensure that the tires are heating evenly across the face, but that is to better judge whether they are getting max traction.

wombat

Thanks for the replys guys. I think i'ma inflate them a little bit and run them for a good amount of miles and see if it wears unevenly.

DrPuttsSS/SC

I think that when Chevy picked the recommended inflation for our cars they took everything into account, not just ride quality. For example, they spent so much time and energy tuning the SS/SC suspension on the Ring that I am sure that the tire pressure was played with and optimized for handling as well as ride and tire wear.

My experience has been that you can adjust your pressure up or down a few pounds from what is recommended. As you said, get a tool to accurately measure the tread depth and check it every 1K miles or so and see how it works out for you. Some people like to corner hard while others don't, and that has a big effect on tire wear too. Hard cornering wears the edges of the tread more than just running in a straight line, so you can adjust the pressure to your driving style. Use an accurate tire pressure gauge, also.

It seems crazy that Pirelli (or whoever) told you to pump em up to 45 because that is so much higher than stock and so close to the max pressure marked on the tire. The only people who would really benefit from you doing that would be the tire manufacturers!

just my 2 cents, your reallity may differ

wombat

Thanks for the reply Randy...I also found it weird that Pirelli told me to inflate them so high, which is why I came here for input first.

Anyhow, after school today I'ma run out and pump then like 9psi. (to 41ish)

joeworkstoohard

i was reading my manual today, and even in the book it says that on the SS/SC, if you're going to driving at over 100mph for extended periods to pump it up to 35.

soooo, yeah, i think 45 is a bit much.

alleycat58

41 is still quite high. 42 is the absolute maximum I run, and that's running a road course for an hour and a half at speeds up to 145 miles per hour. Highway the max I'd be willing to push it to would be ~37psi.

DrPuttsSS/SC

You're certainly welcome!
I don't know how clear I made it in my last post, but maybe this will help, just something to consider.
I love to corner hard. I often take freeway on/off ramps at 80-100 and like to zoom around corners even in town. I have to watch my coffee cup cause I love to cut the wheel hard and zip onto a side street. So my tires wear more on the outside of the tread than they would for some people, and I can run a few pounds more pressure to make the center wear more to keep up with the outside edges.
That's what I was trying to explain about adjusting pressure to your driving style, I hope this made more sense.

Good luck again, and let us know how it works out for ya!

an0malous

the number on the tire is the MAX, meaning "run me at this inflation, and i may blow your leg off one day as your walking past after a spirited run"

suggested PSI on the door panel is your best bet.

07cobaltss

there is a TSB for this.