OK, so we have a 2003 chevy tracker 4 door wagon (weighs something like 3500 lbs).  The stock tires were 205/75-15's and the factory specified 26 psi for the tires (stamped on the inside of the door pillar).

Now that I have fit 235/75-15's, what tire pressure should be used for the street to give a good ride without wearing out the treads due to under/over inflation?

The exact same pressure.

I dropped the pressure when I went to
bigger tires, on 235s I went  down 2-3
PSI, tho my data plate said 23 PSI stock

Wild

As i seein your name you have good taste but with the tire pressure it depends on the max it can take wether it's a P or LT rated blah blah blah so whats the max T/P on the 235's?

You DO NOT want to run "MAX" tire pressure in your rig!

Yes, you will get the best gas mileage, at 35 psi, but it will SIGNIFICANTLY effect handling if you run the pressure that high!

You may not notice it in the city.  My daily commute includes over 20 miles of twisty mountain roads, and you really notice the difference in handling, between the "door pillar" pressure, and the 35 PSI that even the Goodyear Dealer wants to put in my tires.  Both of my Sidekicks, and my wife's Grand Vitara handle best, at the door pillar tire pressure.  It's there for a reason!

OK....I'm going outside now with my trusty tirepressureguage to set the pressure down to 26 psi.  I'll test it out on the drive home from work today.  I bet you it will scream like crazy taking corners, but maybe it will be ok.

We'll  see.....

Here is an article on tire pressure.
http://www.sportcompactcarweb.com/tech/0208scc_tires/

Here is a snippet from that article;
"the following rule of thumb from Oscar Pereda, an engineer for BFGoodrich. He calls it a "realistic starting point," saying it has never been just right, but is a good place to start. The rule is:

(Vehicle Weight in lb/100) + 2 psi at heavier end + 2 psi all around if suspension and alignment are stock.

Example: Stock 911, 3,000 lb.
(3000/100) = 30 psi
Add 2 psi all around = 32 psi
Add 2 psi to heavy end = 34 psi at rear
With modified suspension, the result is 30 psi front, 32 psi rear."

Here is another article which goes into detail with pressure in reguard to temperature.;
http://www.tirerack.com/tires/tiretech/general/airpress_tempflucts.jsp

However if you use the drop down box, you'll get lots more information on tire pressure.


My experience with our 4 door was when on 215's-235's range, the recommended tire pressure on the door jam was very adequate.  ~26psi

As we've gone to larger tires we've reduced the pressure.
I think on the road now we use ~21 psi.   (on 315x75xR16's)

Just watch your contact patch, tire wear, and tire bulge.  Then drive it.  You'll eventually find a good pressure for your tires and driving styles.

~Nate

you guys keep saying 35 psi or 26 psi but that if it's a passanger tire not a light truck.

after driving in water and a bit of sand on the road, pull over and have a look at your contact area.  I had 1 inches contact  in the middle of my 33x12.5 s when the tire place first put it on at 26 psi. I now run at 17, looks to wear even

you guys keep saying 35 psi or 26 psi but that if it's a passanger tire not a light truck.

I can't imagine 35psi in any tire for our trucklets.  It would be like driving on solid wagon wheels.  (bumpy)  Plus you'd wear out the center of the tire long before the outter lugs.

It might drive like a dream with 35psi at first, light on the steering wheel, little rolling resistance, better milage, etc.  But as soon as it wore down a bit, it'd feel like it was back to normal, but then you've got a half bald tire.

~Nate

If I'm going on long drives, I'll set the tire pressure to about 30 psi. Since I commute 60 miles roundtrip a day I usually keep it there. But like most have said, it will handle better with a lower pressure but you'll suffer a lil faster wear and poorer gas milage.

So I don't really recommend 30 psi, I'm just saying I'm too lazy to get my fat ass out and set all 4 tires down 5-6 psi. Actually last sunday I was out playing in a foot of mud..... at 30 psi!

I have 215/75's on my SWB, I run them at 30psi in the front and 28psi in the rear, it's a little hard on the bumps but I find it better in the turns than when I had them at 26psi. Plus my mpg is better. I noticed more "roll" with the lower tire pressure.