Highway air pressure

What is everybodys opinion on a highway air pressure for 32x10.50 TSLs on 8" wide 767s?
Just stuck them on there and looking for opinions. Right now they are sitting at 30lbs.

Andy

my 33 12.50's are running at 35 psi and i have no abnomal wear for over 60,000+ miles.

how much lift did you get with the dakota leafs?

DARKFLY said:

my 33 12.50's are running at 35 psi and i have no abnomal wear for over 60,000+ miles.

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60K?? you must not mean TSL's.... Andy, are we talking about Radials or Bias plys?

-Scott

you take chalk.. and draw a fat line on all 4 tires... then drive around the block and look at the lines. If the middle is more worn then outside, you need to loose some air, if outside is more worn then middle, add air... if even wear you're good.... Repeat again to test...

Btw, don't drive too far or you will wear the chalk off and test will be null.... around the block, half a block... 500 yards... just stop look and drive a bit more..

Kejtar

They are radials.

If I do the chalk thing better do it in a straight line, welded rear makes some nice howling around corners.

First time driving TSLs down the highway for me, they really sing

I have had this XJ over a year, but just now put a tag on it for the heck of it.

sintax there bfg muds and yes there is still quite a bit of tread left. there going to weather rot before they wear out

Kejtar said:

you take chalk.. and draw a fat line on all 4 tires... then drive around the block and look at the lines. If the middle is more worn then outside, you need to loose some air, if outside is more worn then middle, add air... if even wear you're good.... Repeat again to test... Kejtar

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No offense, kevlar, but I suspect this chalk method has an accuracy of ±10psi. What pressure are you running on your tires? I run my 10.50's at between 24 and 28 psi. Each time I rotate my tires, I check tread depth across the width of the tire in 3 or four places around. On the average, even at 26 and 24 psi, center wear is greater than the outside edges. A 12.50 wide tire should require even less pressure.

I can't imagine running 35psi in a lifted XJ. It must ride like a dump truck. Mine almost does as it is.

I run my 31x10.5's at 35psi usually and I have 33K on the tires right now with even wear, probably have about 3K miles left before they're dead. I've run them at 30psi before too and it drives nicer, but I get better mileage at 35psi and haven't seen any uneven tire wear.

I ran right at 34 PSI for 70k on my old 33" ProComp MTs. The only reason I had abnormal wear was because of bad ball joints and extended wheelbase (+4) . So I had noticable scrubbing and feathering. Depending on how much your Xj wieghts, it could vary greatly. I ran a little high because I carried a fulsize spare, two high lifts, etc, etc. On a lighter Xj, 28 to 30 prolly is about right. I know there is a mathematical calculation for figuring exactly what PSI you need depending upon wieght and tire size. some one might know it here.

MATT

20psi for normal street use. They are at 25 psi for the fully loaded highway drive out to Moab tomorrow. They are 285/75R16 MTRs on 8 inch wheels. Those tires have about 10K miles and they are wearing nice and even. I don't know how you guys can stand driving lifted Cherokees at 35 psi.

I only have 31's on mine, but I am running 28 pounds of pressure and they wear a little more in the middle. I can't imagine running 35 myself. My last set of 31's I ran 26 pounds and got 70K miles on them. They were KO's though.

Curt

When I'm not loaded up I go 23 lbs. front, 19-20 rear. With a 33x12.5. Seems to wear flat, but have never measured it. Came to this conclusion using Kevlar's chalk technique, just take some time a try multiple pressures, you'll get very close. Just recheck every so often.

Some might say that running the lower pressures will heat up the tire and it will wear faster, I've never noticed this to be a problem at the pressure I run (ran this pressure with my previous GY MT's and currently w. MT/R's. And at the end of their life, the MT's treadware was quite flat).

It also rides better on the hwy. compared to someone that is running 35 lbs. 35 lbs will ride way too harsh. Ride quality is already compromised the way we set up our rigs, let the tire pressure help out some. Sidewall flex isn't much of an issue either, I never try to achieve 1G hitting the on-ramp!!

Oh, And airing up and down is'nt as time consuming.

MaXJohnson said:

No offense, kevlar, but I suspect this chalk method has an accuracy of ±10psi.

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Actually this method has given me a nice even wear on my AT's I drive about 120+ miles on the freeways each day and the wear is very even. I currently run 32psi in my 31's

Kejtar

MaXJohnson said:

No offense, kevlar, but I suspect this chalk method has an accuracy of ±10psi. What pressure are you running on your tires? I run my 10.50's at between 24 and 28 psi. Each time I rotate my tires, I check tread depth across the width of the tire in 3 or four places around. On the average, even at 26 and 24 psi, center wear is greater than the outside edges. A 12.50 wide tire should require even less pressure.

I can't imagine running 35psi in a lifted XJ. It must ride like a dump truck. Mine almost does as it is.

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MaX, the chalk method actually has an accuracy of closer to about +/- 4 psi. However, it has a built-in caveat: all it can tell you is the right pressure to keep the tread flat on the pavement. If you run a very wide tire on a narrow-"ish" wheel, that pressure may be too low for safe operation. If the chalk doesn't wear evenly until you get down around 22 to 24 psi, I'd kick them up to 26 if you just drive locally, or 28 if your daily driving includes highway miles. Otherwise you risk becoming an Explorer/Firestone wannabe.

I run 28PSI on my 33x10.50 BFG M/T's on 15x8 Canyon wheels. they wear and ride perfect. On the trail I run 11PSI.

Correct tyre pressure formula

I have read a lot on recommended tyre pressures and would like to add my own personal experience on the subject. One thing you have to remember is that there are a few factors involved. One to remember is that it is the air volume and not the pressure that supports the weight, so to get the same amount of air in a small tyre will require more force and therefore pressure than the same amount in a larger tyre. i.e.. 35 psi in a 30"x9.50" tyre may have the same amount of air in it as a 33"x12.50" with 30 psi. I used to have a lot of punctures on my outback trips from stones getting forced into the tyre casing through the sips, (the cuts that are put in the tread blocks). It turns out that having too much pressure opens up the sips and makes it easier to get the stones in. After 7 punctures on that trip and finding that the centre of the tyres had worn I knew that I had to find a better way of getting the right pressures. As it always happens after the fact, I read in a 4x4 mag after I got back that to find the right pressures for different temperatures, loads and conditions you take front and rear pressures cold, and then again immediately after at least 20 minutes at highway speeds or more and there should be a 4 psi increase. If there is more than 4 psi, than you had too little to start with and if there is less than 4 psi, than you had too much. I have used this technic for the last 5 years and didn't suffer one puncture from stones again, (had a steel railway spike go through the trailer tyre on the old Ghan railway line) on the same roads, temperature and loads. The tyres have also lasted longer with very even wear. You can use this technique for your trailer as well. For my tyre size (275x70x16) and load, I run 33 psi in the front and 32 psi in the rear. My mate in his XJ ended up with 35psi front and rear with 30"x9.5"x15 's and later with 33 psi front and rear with 31"x10.5"x15 's. I ended up with less in the rear because I don't carry much in the back of the car, most of it is in my trailer.

I run mine at about 30psi, 35" BFG Muds.

How can I stand it? I only drive my rig about once a week....... or less.