Tire Preasure

What preasure should i run my 33x12.5 BFG MTs?

I run mine at 30psi. You can run more just dont go over the tire max which should be 44psi. Also i wouldnt run anything less then 25 or else you run the risk of ruining the tire, you will get what is called run flat wear in the tire. It is rubber powder that if it covers a quater then the tire is bad. Anyway its up to you the more presure you have the harder the ride will be.

Get some sidewalk chalk from the toy department of Wal-Mart (or steal some from your kids if you have any). Go to a parking lot where you can drive straight ahead for atleas 100 yards. Draw a nice, thick chalk mark across one front tire and one rear tire. Drive straight ahead 100 yards. Look at the chalk marks. If they are more worn on the edges than in the middle the tire is under-inflated. If they are more worn in the middle than on the edges the tire is over-inflated. If the wear is even the tire pressure is good.

Simple.

dmillion said:

Get some sidewalk chalk from the toy department of Wal-Mart (or steal some from your kids if you have any). Go to a parking lot where you can drive straight ahead for atleas 100 yards. Draw a nice, thick chalk mark across one front tire and one rear tire. Drive straight ahead 100 yards. Look at the chalk marks. If they are more worn on the edges than in the middle the tire is under-inflated. If they are more worn in the middle than on the edges the tire is over-inflated. If the wear is even the tire pressure is good.

Simple.

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Sound advice. The load range for 33s is much greater than that of say, stock 225s, or even 31s, so less air is needed to maintain the appropriate load range of your vehicle, unless your rig gained weight as you went up in tire size.

I run between 30-32PSI in my 30x9.50 MT/Rs and found this to be perfect. Also don't forget that prolonged driving on the tires will cause the air pressure in them to heat up, causing the PSI to increase as well, so you have to play with your air pressure a bit before finding a perfect medium for what to run in them.

I run my 33X12.50's at 22-23psi. This is on a 8" wheel. On a 10" wheel, I'd up the pressure to 25-26psi for a starting point.

I used 26-28psi for 31X10.50's on the same 8" wheels. The result was 60,000 miles with enough tread left to sell the set for over $100.00

weight, tire width & diameter, wheel width and sidewall stiffness all factor into the resulting pressure.

Tire pressure should always be set cold. Run-time heat increases are factored into recommended settings.

Re: Tire Pressure

I have a 97 with 32x11.5x15 GY MTR's on an 8" rim.

what should I run for air pressure?

I read somewhere that I should check psi, drive 20 minutes or more on freeway, check psi. Should go up by 4psi. If if goes up more, then have to little, if it goes up less, than have to much.

On the sidewall it says Max psi is 50. So I thought 35 would be a good start. well, I am down to 30psi and still only getting a 2-3psi difference.

anybody else ever use this?

what should I run for psi.

Re: Tire Pressure

Red97XJ said:

I have a 97 with 32x11.5x15 GY MTR's on an 8" rim.

what should I run for air pressure?

I read somewhere that I should check psi, drive 20 minutes or more on freeway, check psi. Should go up by 4psi. If if goes up more, then have to little, if it goes up less, than have to much.

On the sidewall it says Max psi is 50. So I thought 35 would be a good start. well, I am down to 30psi and still only getting a 2-3psi difference.

anybody else ever use this?

what should I run for psi.

Click to expand...

As it says above... take a chalk, draw a line, drive it around the block and see how/where it wears: if outside, add pressure. If inside, drop pressure. If even.. you're good to go.

Re: Tire Pressure

Red97XJ said:

On the sidewall it says Max psi is 50.

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you probably already know this, but just to make sure. the max pressure shown on the sidewall of a tire has no relevance to the correct pressure for your vehicle. that's just the max pressure that GY has designed the tire for. they have no idea what jeep or onyone else intends to do with it. that's why jeep tells you the correct tire pressure for a stock XJ, not GY. now that you'v changed tire widths though, neither is gonna tell you what psi to run.

anyway, the chalk thing definately works. but your check/drive/check thing might work too. i just never heard of that method. you should expect to run lower pressure for wider tires though, so if you're headin below 30, then it seems you're on the right track.

maybe, just keep goin with your method, get to the 4 psi diff, and then just verify that the chalk pattern is right. i'm curous if/how the 4 psi thing works? interesting for sure. i assume that you can only do this once and then you have to wait for the tire (and air inside) to cool back down before you can do it again? sounds time consuming. you could always do the chalk first, then verify with the check/drive/check. either way, you should arrive at the same result.

do you remember where you read about this method?

I read on it one of the privat XJ sites from Australia. Can't remember which one, but this guy swore buy it, he had gotten it from a 4x4 magazine. He claims to of always had tire problems until he did this.

It may seem time consuming, but I have been checking mine in the am when its cold, then I drive to work and check when I pull in the parking lot.

I am going to try the chalk tommorow.

What do you other guys run with 32's? What does everyone feel is safe for the trail. I am a newbie so help me out!

Jason

97 red, 3.5RE 32" 2hitches, roof rack in the mail, spending more....

Red97XJ said:

What do you other guys run with 32's? What does everyone feel is safe for the trail. I am a newbie so help me out!

Click to expand...

Remember that other's pressure should not be used for comparison just for a starting point as the weight difference (even due to different lift kits or addons) as well as difference in tire make/model (and its age) will make a lot of difference.