JKU Hammerhead
New member
I just installed 33s and the tire shop set them at 42psi. Is that too high? Should they be around 32psi? I dont mostly highway driving.
Psi on 33in General Grabber AT2
- Thread starter JKU Hammerhead
- Start date
kaptkrappy
New member
For starters, never go back to that tire shop.
42 psi is not even in the ballpark. They are supposed to go by the recommended factory pressure which is listed on the sticker in the door jam. That's SOP.
I run 30 psi in my 33" Cooper A/T's. I get the best ride and best "contact patch" for my 2 door.
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42 psi is not even in the ballpark. They are supposed to go by the recommended factory pressure which is listed on the sticker in the door jam. That's SOP.
I run 30 psi in my 33" Cooper A/T's. I get the best ride and best "contact patch" for my 2 door.
.
radleyhardy
New member
28-32 is a good range for 33's
Red Knight15
Caught the Bug
I run 28psi in my 285/75/16
USMC Wrangler
New member
The one and only shop local to me almost always puts tires at the max cold psi. Thankfully I noticed zero sidewall on my work ride and aired down. I wish I had another choice in shops, but now I know...
On my Jeep, I'm running 32-35 on 255/80R17 KM's and seems perfect on road. Discount Tire in Odessa recommended 40. I told them start at 35 and I will adjust from there, which they did.
On my Jeep, I'm running 32-35 on 255/80R17 KM's and seems perfect on road. Discount Tire in Odessa recommended 40. I told them start at 35 and I will adjust from there, which they did.
Wardell
New member
Yeah, somewhere in the 28-32 range is probably where you want to be for 33s. The best pressure has to do with a lot of factors, like the kind of tires you have, the width of wheel they are mounted on, as well as the total weight of the Jeep (depending on if you have heavy after market bumpers or armour, etc).
The best way to know exactly what pressure to run at is to do a "Chalk Test." Basically, take a stick of sidewalk chalk, and draw a thick line across the tread of at least one of the tires. Then drive a short distance in a straight line across a smooth surface (like an empty parking lot) and look at the chalk to see how it's coming off (it doesn't take much, maybe 5 or so revolutions of a tire). That will give you an idea of the wear pattern. You want to try to get the chalk coming off evenly. If it wears off more in the centre than the sides it's over inflated, and if it wears off more on the edges you're under inflated. It's probably a little easier to be bold and start with a higher PSI than you know you will need, and then let out a PSI or two at a time until you get to the right spot, rather than starting low and adding air. After you get it even, set all the tires to the same pressure and you "should" be good.
I say "should" because you might also have to factor in how the ride feels, which can be very subjective. Even with the right wear pattern, you might find that the ride just doesn't feel "right" to you after a week or so of driving (probably depending on the load range of the tire, because higher rated tires will likely feel stiffer), and you may want to adjust even further to get it where if feels comfortable. Even though you may be sacrificing a bit of extra wear, you might be happier with the end result. I wouldn't change more than a couple PSI for this though (and if you need to, maybe invest in a different load range tire after these wear out).
The best way to know exactly what pressure to run at is to do a "Chalk Test." Basically, take a stick of sidewalk chalk, and draw a thick line across the tread of at least one of the tires. Then drive a short distance in a straight line across a smooth surface (like an empty parking lot) and look at the chalk to see how it's coming off (it doesn't take much, maybe 5 or so revolutions of a tire). That will give you an idea of the wear pattern. You want to try to get the chalk coming off evenly. If it wears off more in the centre than the sides it's over inflated, and if it wears off more on the edges you're under inflated. It's probably a little easier to be bold and start with a higher PSI than you know you will need, and then let out a PSI or two at a time until you get to the right spot, rather than starting low and adding air. After you get it even, set all the tires to the same pressure and you "should" be good.
I say "should" because you might also have to factor in how the ride feels, which can be very subjective. Even with the right wear pattern, you might find that the ride just doesn't feel "right" to you after a week or so of driving (probably depending on the load range of the tire, because higher rated tires will likely feel stiffer), and you may want to adjust even further to get it where if feels comfortable. Even though you may be sacrificing a bit of extra wear, you might be happier with the end result. I wouldn't change more than a couple PSI for this though (and if you need to, maybe invest in a different load range tire after these wear out).