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Tire air pressure

B

bl87xj

NAXJA Forum User
Location
So Cal
Running 33x10.5 BFG AT's on an '88XJ with RE 3.5 SR lift. With stock wheels

Tires are currently at about 30-35psi. But the outer most treads (inside and outside) are not even getting dirty. Leading me to think they are over inflated, but it seems kind of odd to run them any less than 30psi.
 
It does feel odd, but the width of the tire on the stock rims is working against you. I'm not sure what pressure to run, but there's an easy way to find out.

Get some chalk, an air pressure gauge and take the jeep to an empty parking lot. Draw a thick line across the width of the tread, and then drive it straight for 100' or so. Have a look at the line and note it's condition. If the centre is missing but the edges are still there then it's over-inflated. If the edges are missing but the centre is still there then it's under-inflated. If it's evenly worn, you've got optimum air pressure!

:)
 
ok, so your tire is looking like a q tip right, so let air out, I have 33 12.50 on a 8" rim with only 22# of air in the rear an 25 in front, rides good there for me, but thats me not you.. everybody likes different ride, so go with what looks an feels good an safe for you
 
The tires are definately high in the center, I thought they were way over inflated. I was kind of surprised to see they were only at about 32psi.

So I will let some air out and see how it goes.

I posted the question because based on what I see I would not be surprised if I am down to 25psi before the tread hits evenly.

No concerns on running 20-25psi? For around town driving.
 
I am running 34"x10.5" LTB's on a stock 7" rim. I have to run at around 20-25 lbs. to get them to wear even. Seems to be working well so far.
 
I just let them down to 25psi. Going to see how that does.

At 30-35, the armor all was still on the inside and outside treads after about 100 miles around town.

BFG lists the 33x10.5 to have a load rating of 2620 lbs. at 50psi. What does an XJ weigh, maybe 3500 lbs. with a driver and passenger?

I can't imagine running less than 20psi. I am thinking I will end up somewhere between 20-25.

The 285/75-16 BFG AT's on my excursion are at 60psi. I got over 85K miles out of the first set and only rotated them a few times!!
 
bl87xj said:
The tires are definately high in the center, I thought they were way over inflated. I was kind of surprised to see they were only at about 32psi.

So I will let some air out and see how it goes.

I posted the question because based on what I see I would not be surprised if I am down to 25psi before the tread hits evenly.

No concerns on running 20-25psi? For around town driving.
Click to expand...
I'm in the same boat with BFG 33X12.5's on 8.5" rims. I run at about 33-35psi and treadwear is mostly in the center. I don't want to go lower because my daily commute is about 80 miles.
 
bl87xj said:
BFG lists the 33x10.5 to have a load rating of 2620 lbs. at 50psi. What does an XJ weigh, maybe 3500 lbs. with a driver and passenger?
Click to expand...

4000# plus
 
BFG lists the 33x10.5 to have a load rating of 2620 lbs. at 50psi. What does an XJ weigh, maybe 3500 lbs. with a driver and passenger?


This is with the right size rim to match size tire, you have yours on stock rims right?
 
bl87xj said:
The 285/75-16 BFG AT's on my excursion are at 60psi. I got over 85K miles out of the first set and only rotated them a few times!!
Click to expand...

Different animal....those are high pressure tires.....I run 20/22 psi in my 12.5/33 tsl's on the Heep....no problems....I haven't settled on a pressure for my 12.5/33 Pro Comp Xtreme MT's on my MJ yet...it's a DD...right now I have 25 in them. I did a home shop toe-in...will get it checked professionally this weekend, then work on tire pressure.
 
XJPhoenix said:
It does feel odd, but the width of the tire on the stock rims is working against you. I'm not sure what pressure to run, but there's an easy way to find out.

Get some chalk, an air pressure gauge and take the jeep to an empty parking lot. Draw a thick line across the width of the tread, and then drive it straight for 100' or so. Have a look at the line and note it's condition. If the centre is missing but the edges are still there then it's over-inflated. If the edges are missing but the centre is still there then it's under-inflated. If it's evenly worn, you've got optimum air pressure!

:)
Click to expand...



x2 I do that and I run 35x12.50s at 26psi on a DD. Takes about 10 min to figure out what you need to run them at. Just keep letting out air until the chalk wears evenly.
 
so i take it 31x11.5s on 15x8 rims, with ~22psi is safe enough to daily drive?
 
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