84supersport

Which pressure do you use? The pressure on the door or the pressure on the tire? I have 31x10.50s and i'm sure the load rating is much higher than the donuts that originally came on it.

maverickdan

always go with the presure on the tire

Borego

Wrong
It all depends on what your doing?

ZachsXJ

I have 31s and was wearing down the center tread really fast at 30lbs. I've since dropped that to about 22psi and its working great.

if you want to get precise about the proper tire pressure you can do this: "A more involved check is to place a chalk line across the tread face, drive a short distance straight ahead on a smooth surface and then observe the chalk line. You are looking for it to be evenly worn off the tread. Another variation is to measure the length of the contact patch and make it even front and rear."

It was taken from this website: http://www.4crawler.com/Diesel/Tires.shtml

EndlessMtnFab

I like the chalk method.



Zach, my way is more accurate. https://www.cherokeeforum.com/f2/how...52/#post238081

ZachsXJ

I'm too lazy to do that...but I spent hours making my front door removable today :Rofl:

84supersport

Its for street use. They're Mastercraft M/Ts but i'm concerned about them wearing evenly. I'll try the chalk thing. But for the most part, what pressure are you guys running in a 31x10.50 on 15x8 rim? I will try this on 275s I have on the rear of my Monte Carlo too since they wear faster in the center. But that may be from spinning them on the pavement.

danimal

Just an example. I had a set of AT tires on my truck. The rating on the sidewall of the original set was 35 lbs cold. I took good care of them and watched inflation, balancing, and rotation and they worked out fine. One day I had a side wall cut on one of them and had it replaced on warranty. I got the same make and model of tire with the same tread pattern. You couldn't tell the difference by looking at them.

Here's the weird part.

The new tire was rated at 65 lbs cold on the sidewall of the tire.

I ran them for a year maintaining the rated pressures in the tires despite being such a huge difference (35 lbs cold on the old and 65 lbs cold on the new). The tires were wearing fine and had no issues with them old or new.

I eventually ended up selling those rims and tires on ebay and replaced them with the BFG Mud Terrains that came on the wife's new Rubicon when we lifted hers and put bigger tires and new rims on it.

What does all this mean??????????

Beats me.

mike albo

I have allways gone by whats on the tire,then made adjustments from there.Usually less PSI.

dhrider707

Well it's likely that your 31's are a load range C or a 6 ply tire with a max 50psi (2270 lb per tire). You are absolutely right that the LRC are can carry more load than the factory P215/75r15 or even P225/75r15 with are only 4 ply and max out at 35psi (1742 lb per tire). Keep in mind that each tire manufacturers figures may differ slightly but will be very close. As a rule for folks in the tire industry the door placard will give proper pressure as long as you stay within the tire spec'd on the placard. When you go from a P (passenger rated) to an LT (light truck) things do change.

Generally when someone wants to go up in tire size I consult a "load and inflation table" for that manufacturer to figure the proper psi for whatever vehicle the customer has. Here is an example http://www.olderogtire.com/pdf/light...ion_tables.pdf

In this case 31x10.50r15LT: at 35 psi 1765 lb per tire x4 can carry 7060 lb...the XJ has a gross weight of 3057lb obciously overkill for the everyday application. If I had a more complete load table available to me I could better figure a more accurate psi. I will tell you that I run 30 psi cold which is lower than the 33psi on the door placard. Take in to consideration what you are loading up in your ride (passengers, gear) and adjust psi accordingly. Hope this helps.

muddpigg

ya'll can scoff at this if you want - but i run 31 bfg A/Ts and i keep 40psi in them during the winter/cold months and 35 in kinder weather. if i'm going to get off the pavement i adjust down 5psi. have had these tires on the heep for over a year now, keep them rotated and balanced regularly and have no visible wear what so ever. i guess it helps that i work at a tire shop.

wear in the center indicates overinflation
wear on both outer and inner edges indicates underinflation.
wear on one side or the other or anything other than even wear is very likely a mechanical issue, get it checked immediately.
do your next tire tech a favor when u get a nail/flat, don't use fix-a-flat - use your spare! fix-a-flat makes a god-aweful mess inside your tire and patches almost never stick.

rdeskater

great thread, lots of good info. I've been running 30psi on my firestone destination m/ts they feel good but look like they might be a little bubble shaped so I'm going to try the chalk line method. the tire shop told me to run 40psi when they installed but they rode really hard and bounced me almost through the roof. we'll see what the chalk line tells me when this storm blows out of here.