[MeloYelo]

I know that this topic has been discussed over and over again but I had a question regarding the chalk test for getting the tire pressure set correctly.

I just put on a set of 35x12.5 Mickey Thompson MTZ.

This pic is the tire at 22psi. Looks over inflated so I took it down.



After doing the chalk test again, I end up running at 13psi. Does that seem low to anybody else?

[DaOne]

Way too low...IMO, the chalk test sucks. See this thread for a better formula...

http://www.jeepforum.com/forum/showt...ght=chalk+test

[MeloYelo]

When I do the math that is suggested in that thread I come up with 15psi. Still seems kind of low.

Weight of jeep: 4450
Max psi on tire: 35

4450 x 35 = 155750

Max load on tire: 2535

2535 x 4 = 10140

155750 / 10140 = 15.35

Did I do that right?

[Whybu1]

Yeah using the math formula I came up with something like 12 psi for my current combination.

[Wheelin98TJ]

Yes, you did the math right.

You're going to have to air them up a little and deal with the uneven treadwear. 15 psi is too low for the street.

I'd continue to run them at 20-22 like you had them at previously.

[TheBoogieman]

I've got the exact same tires on my 98'.My brother emailed MT about his 33's and they told him to run 22psi.I emailed them and never got a response.I've got 24psi in mine now and the side tread looks like it's 1/4-1/2" off the ground.I hate to go below 20psi,so I guess I'll see if someone answers your question.Sorry I couldn't help.I'm in the same boat

[MeloYelo]

Thanks for the help guys. Looks like I'll air them back up to the 20 range.

[DaOne]

Originally Posted by Wheelin98TJ

Yes, you did the math right.

You're going to have to air them up a little and deal with the uneven treadwear. 15 psi is too low for the street.

I'd continue to run them at 20-22 like you had them at previously.

Doesn't some of the wear depend on the width of the rim? I mean, with a 10" rim, the wear will be more even at 20-22lbs than it would be with an 8" rim at the same pressure. At least that's what I always thought.

[Wheelin98TJ]

Originally Posted by DaOne

Doesn't some of the wear depend on the width of the rim? I mean, with a 10" rim, the wear will be more even at 20-22lbs than it would be with an 8" rim at the same pressure. At least that's what I always thought.

Yes, wheel width is a factor.

[MeloYelo]

That may be what makes the difference. I am running a 15x8 rim.

[DaOne]

Originally Posted by MeloYelo

That may be what makes the difference. I am running a 15x8 rim.

Yeah, you'll get more bulge. I know I get good wear with my 33x12.5s on 15x8s and I run around 28lbs on the street.

[blueknight44]

For street use I always inflate to max pressure, my wear is even with rotation of the tires. Remington Wide Brutes 30 x 9.5 x 15
50 psi cold

[Wheelin98TJ]

Originally Posted by blueknight44

For street use I always inflate to max pressure, my wear is even with rotation of the tires. Remington Wide Brutes 30 x 9.5 x 15
50 psi cold

How are you getting even wear running max psi?

[[ITA]Tsunami]

Originally Posted by blueknight44

For street use I always inflate to max pressure, my wear is even with rotation of the tires. Remington Wide Brutes 30 x 9.5 x 15
50 psi cold

50 psi is the max psi cold for a single tire, it's waaaay to much pressure. And by the way it's unsafe. You are playing at the limit of your tire max pressure rating. For a 30x9.5x15 if it is a load C range (i guess so) you should aim at 30-32 PSI cold.

To the OP: i run my mtz at 20-22 PSI cold.

[mdm]

Originally Posted by blueknight44

For street use I always inflate to max pressure, my wear is even with rotation of the tires. Remington Wide Brutes 30 x 9.5 x 15
50 psi cold

Originally Posted by Wheelin98TJ

How are you getting even wear running max psi?

The tread and sidewalls of those tires must have the same ability to flex as 1/4" steel plate.