andrewenglish

...what tire pressure do you run for highway driving? When I got mine balanced they inflated to almost 42psi... I took them down to 35psi because the ride was so damn harsh. However, what provides better gas mileage / wear? Should I move it back up to the 42psi?

They're mounted on 8" wide rims (tires are 12.50"), so I also don't want them wallowing around on corners which means higher pressure too I suppose

black label

I don't have 33's but I'm a geek about tire pressures. Higher pressure can improve had mileage by reducing resistance however too much pressure can bow out the center of the tread reducing contact patch and causing premature wear at the center of the tread pattern. This also reduces traction and increases braking distance.

On the other side, low tire pressure can reduce gas mileage by increasing resistance. Also, low tire pressure can cause your sidewall to become part of your tread. This is extremely dangerous as the sidewall is the thinnest part of the tire and continuous driving on low psi can cause a blow out, on a lifted vehicle with 33's tho could lead to a roll over (think ford explorer/Firestone tires).

Centralgrand

42lbs sounds insane...

I always liked 30psi... 35 always seemed a bit much and harder to control in the bumps on the interstate.. no cushion, felt like I was riding on 2x4s.... But that was driving my own rigs, not yours...

andrewenglish

So any ideas about optimum pressure?

I'm aware of all the side effects, that's why I'm trying to find a good balance. These tires were expensive so they need to last lol. I think I'm probably fine anywhere in the 35-45psi range, but I just want the optimal setup

andrewenglish

Ah, thanks centralgrand. Yeah I'm new to working on cars (see my build thread) but damn, even I took a second look at the pressure monitor. How're your tires wearing at 30?

Centralgrand

When I ran 33's not bad at all.. nuthin that significantly alarmed me. I like 30psi... Even in my 35s now.

I think you should shoot for 30 and adjust from there...

2KXJJEEP

I'm running 33x12.50 on 8" rims and iv always ran round 30psi and they r wearing great

mrfajita

30? Both my sets of 33s I have run at 20 and 18 (20 in the baja claws, 18 in my SSRs)
Any higher and the full tread doesn't contact the road. And I have done longish trips sustaining 55-65mph on both sets and they never exploded on me.

andrewenglish

Dude your gas mileage must be miserable lol

mrfajita

Not a lot worse than it was on 31s. fuel is cheaper than tires, so I'd rather get a few less mpg than wear the center out prematurely on a set of $300 a piece tires (got them used for way less than that but still)

andrewenglish

I get ya. Both situations suck when you're broke though

Centralgrand

I'm kinda a bit of an air pressure nerd myself... offroad though, not so much on... I'd be lying if I said I didn't drive an hr home @70mph at 24lbs or so... Never had a problem or noticed anything scary.

In the winter we go down to 3ish and airing all the freakin way back up to 30 when you've had a long weekend... well..

holycaveman

Honestly I run 42psi. With 30psi I can feel the jeep is harder to pull hills and such. No doubt from the softer tire. Yes the ride is harsh. But my wear is good and turning/rolling is much better.

Off road I am at 8-10psi.

andrewenglish

Looks like I'm gonna put a tad more air in them tomorrow and take note of how it rides (now that I have a rear DS lol). Bicycle pump here I come! hehehehe

Teej

I have 33" MT/Rs and they love to be at 24psi. I drove with them on 30 and they were wearing weirdly. At 24 they're perfect. They're squishy, and no huge hit in mileage.