So I bought a 2010 Rubicon unlimited and decided for some reason I would check the tire preasure with the weather change. Well, door jam sticker says 37psi for 255/75/17s and they were all set to 32psi, with the exception of the spare, which was 35psi. WTF? Is this normal? Obviously I dont have a perfect leak in all 4 tires and it must be the dealer or manufacturer.

 

The pressure in your tires changes with temperature. Air expands and contracts. This is why you should check your tires periodically. A pressure change is normal. All four tires being the same pressure means you do not have a leak and they were all filled to the same pressure at the same temperature. In the summer your tires will gain pressure in the winter they will lose because of the ambient temperature.

If you notice the tire pressure on the side of the tire is listed as "cold pressure". When you drive the air is heated by friction. Also this is the max air pressure for the tire for its load rating. You can run lower pressure but you are also lowering the weight rating of the tire. Most here run a lower pressure to have a smoother ride. But if you go too far your MPG will suffer.

 

I'm just wondering why they didn't air them to the specified PSI indicated on the door jam. The ride was very spongy.

What's a good preasure to run when offroading?

 

THis was pretty much just explained in the above post. Its possible they filled them when it was 90 degrees out side and the pressure would show higher. Then as they cool the pressure will lower.

I run mine at 35 psi, and i check and fill them in the morning while the vehicle is in the shade before any driving has been done.

HTH

Good luck

 

When my 10 Rubi was delivered it had 37 all around. I'm sure that was done by the dealer when it was prepped. The dealer forgot or the tech was old school.

 

For best results, pressures should checked and set when the tires are hot. Typically, setting them between 32 and 35 PSI cold (depending on outside temps) will result in close to 37 PSI when they get to operating temperature.

 

Widewing, did you mean checked and set when cold?

 

This goes against everything I have ever heard. I check the tires when the tires are cold, I believe that's why it says cold tire pressure on the door sticker.
If you check it when it's hot then you're reading temps after they have heated up. If you put air in at that point you will be low if you check it when they're cold.

 

I could see a 2-3psi drop due to temp. change but 5... Even warming the tires up I doubt one would see 5 PSI. Dealer dropped the ball.

Oh, and the door jam and industry say to check and set tires when cold.

 

Um, I've used several tire guages and they all tend to be 2-5 psi difference. Cant find a damn accurate one for crap nowadays.