I have an 03 Av. and I put 275/55/20 highway tires on it. Can you tell me what tire pressure the factory calls for for this tire combination, like on the newer models with 20's?
I think it safe to round it up to 32 Lbsbiggmachz said:my 08 LTZ with 275/55R20 calls for 220 kpa, which is 31.908 psi
Tire Pressure
Here's a way to find a starting place for testing....
Your Av has a GVWR rating. That's the weight of your fully loaded AV.
Your tires have 2 federally mandated pieces of information on the sidewall. Max Pressure, and Max Load. (BTW the max Load is rated at Max Pressure). Please note that the Max Pressure is NOT the pressure you ever want to run a tire at, if you can avoid it. It's the Max Pressure you can put in a tire without it exploding.
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Take the GVWR of your AV and 7,000
divide it by 4 times the Max Load (2535) ? 10,140
of your tire (because you have 4 tires). .69
The answer should be a fraction and you don't need to fully resolve it yet. If the answer is greater than 1, then under no circumstances should you put those tires on your AV.
Now multiply that fraction .69
by the Max Pressure from your tire's sidewall. x 44
The answer is the theoretical pressure 30 psi
you should run your new tires at.
From this starting point you should then test, by driving your AV.
If your handling feels 'squirrelly', then increase the Pressure by 4 psi and test again.
If after a 10-15 mile Freeway run at about 65 - 70 mph your tires are warmer than hand hot (if it is uncomfortable to hold your hand on the sidewall for more than a brief touch) then increase the Pressure by 4 psi and test again.
If your ride feels like it's on rocks, you could decrease the Pressure by up to 4 psi. No more than 4 psi!
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(New Tires Only)
Draw a chalk line across the tread and drive a few revolutions of the tire.
Look at the chalk line.
A: If it is evenly scuffed, you're fine.
B: If it is more scuffed at the edges, increase the Pressure by 4 psi and retest.
C: If it is more scuffed in the center, the situation is this - At the Pressure you want to run them at, your new tires are over-inflated (essentially you bought a somewhat inappropriate tire). You then have 2 choices - 1. Decrease the Pressure until the scuffing is even (and accept poor handling, but maximize tire life) but never to less than 4 psi below that original calculated figure.
2. Leave them at that Pressure and accept that you will not get as long a life as you could have out of those tires. (Note that this could still mean you get very long life, if the tires are 'over-engineered'.)
In the morning, when the tires are cold again, check and note your new tire pressures.
After you get a close approximation of tire pressure using Treehugger's method, make a note of your cold tire pressures. After warming up, you should see an increase in pressure of approximately 10%. If you have more than a 10% increase, the tires are flexing too much and should inflated several more psi and rechecked. Less than 10 % would indicate an over-inflated tire. The Av is very close to being balanced F/R, and correct pressure should be close to equal for all four tires.
was that treehuggers post? one of the best I've ever seen on any forum...Av-n-Taz said:This method was posted here, years ago. Works for me.
EJ
Been that way for a long long time.Av-n-Taz said:p.s. BTW, What's up with, "Left in Disgust"? What did I miss?