Tire pressures for Mud Terrains

Hello,

Just bought a 2004 Jeep Unlimited with a Rubicon Express 5.5" Long Arm lift. It has 315/75Rx16 BF Goodrich Mud Terrain TAs.

Checked the tire pressures last night and they were all 21 PSI cold. That sounds kinda low to me for onroad use.

Anyone know what the correct onroad tire pressure should be?

Thanks

maybe 32.... check your tread contact and adjust from there

Well first what size is that really? 32", 33". I run my 33's at 25 psi on the street.

BingBing said:

Well first what size is that really? 32", 33". I run my 33's at 25 psi on the street.

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I believe those are considered 35" tires. They measure 34.5" from the ground to the top of the tread through the center.

I'm running 28 psi now.

I'll experiment with 25 to 30 PSI

Thanks for the help.

Since we are on the subject, What about 32" BFG MT's

I take them down to 15-20 off road.
I have them at 40 on road.

I believe they have a max rating of 50 psi.

What should I run them to work? 60 miles of city/freeway combined.

Keep in mind the more air the rougher the ride. Play with it and use the amount the vechile likes.

Depends on what you are doing. For 32's on rocks i would go 12-16 psi. Trails and mud closer to 20 psi., low pressure in mud you pinch sidewalls. For the street, no more than 30-32 psi.

JMotorsprt said:

Since we are on the subject, What about 32" BFG MT's

I take them down to 15-20 off road.
I have them at 40 on road.

I believe they have a max rating of 50 psi.

What should I run them to work? 60 miles of city/freeway combined.

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Your max rating, keep in mind, is for a vehicle that uses that tire size as its stock size...and at full load. Being that your XJ is a LOT lighter than that vehicle, you need to keep less pressure in the tires. Jason, you should look at about 28-30lbs and go from there. One thing I like to do to make sure I'm getting a good contact patch is make a 6" wide chalk line going across the tread of the tire. Drive it straight for a few feet, then get out and see what the wear is like. What you're looking for is even wear across the entire tread. If you don't wear the outer chalk, pressure is too high. Less wear on the middle, pressure too low. You'll be amazed how much better the Jeep rides with the right pressure. I deal with this at work on a daily basis.

how does ride vs. gas mileage play into the mix? i understand that the upper 2/3 of max press is the best ride, but how about best mileage? what do you all think?

The harder the tire the less rolling pressure. A steel wheel would get the best mileage but ride like crap. Too much pressure means you wear out the middle of the tire. The key is to find a balance between ride, mileage, traction, and life of the tire. The other thing that comes into play is rim width.

Like was mentioned, doing a tire patch test is probably the best way to find a good pressure for the highway and figures in the rim width. Do a search and you should find plenty on this.