[TwoThousandWJ]

I have a set of Michelin LTX M/S tires on my Jeep. The tire max pressure is 80 PSI, but the Jeep recommends somewhere around 31 to 33. I usually run 43 for better fuel economy and tread wear. However, when driving in snow / ice (not frequently), I want to lower my tire pressure for better traction. What's the lowest pressure that I can safely run for short trips (6 - 10 miles) without damaging the tire, wheels, or Jeep?

 

[jserna]

I use 20-25 psi, on my WJ for snow and other off roading

 

[steve_80]

You usually run 43? Doesn't that warp the tire or something? I was told by the place I had my LTX M/S Defenders installed to keep it at 33.

My last LTX M/S were 33psi for 10 years with near full tread at the end.

 

[ChrisHager]

What size and load range are your LTX's?

I'm running E range LTX A/T2s (Max 80 PSI) on my Expedition. Discount Tire drops the pressure to 32ish at every visit. I crank them back up to 50. Why? I was curious at where the PSI should really be set so I E-Mailed Michelin and told them exactly what vehicle and tires I have. They responded that 50 was the proper PSI.

50 seems a little high to me, including per what my little program says but I figure the tire manufacturer should know best what their tire run at. So far, I have fantastic and even wear.

 

[steve_80]

I just emailed Michelin as well

Mine are the 245/70R16, not sure the load rating (not near my car)

 

[TwoThousandWJ]

You usually run 43? Doesn't that warp the tire or something? I was told by the place I had my LTX M/S Defenders installed to keep it at 33.

My last LTX M/S were 33psi for 10 years with near full tread at the end.

My LTX M/S are load range E. They are actually meant for a heavier vehicle, but they are the smoothest highway tires that I have put on my Jeep, offer decent snow traction, and last forever. The problem I have had with lower air pressure is that I get uneven treadwear. The sides of the tire wear much faster than the centers, even on the rear (front and rear seem to wear at about the same rate for me, selecTrac 99.5% of time spent in 2WD). The downside is that when the tread wears down, at 43 PSI, the ride can be rough and that could be what contributed to my recent heater core leak issue. On highway and freeway, urban areas, the Jeep rides smooth even at 43 PSI. But if it hits a bump or drives over a rail road track, there's more shock / vibration compared to a passenger (load range C) tire at lower PSI.

 

[11B-33T]

I just installed General Grabber AT2s on my WJ and I emailed them after reading the above replies as I'm curious what the manufacturer would say before I tried the chalk test..

General Tires replied:

"The proper pressure for the 2004 Jeep Grand Cherokee with General Grabber AT2 P255/70R16 111S SL OWL is 42psi" :surprise:

Looks to be hella high to me but Chris said they should know so I'm off to air them up.

 

[steve_80]

I wonder if Costco will put 43psi in.

 

[ChrisHager]

What's the load range and max psi on those GG AT2s, @11B-33T?

 

[11B-33T]

What's the load range and max psi on those GG AT2s, @11B-33T?

Sidewall says max load = 2403 lbs and max PSI = 44

BTW, my WJ is 2wd V8 SE

 

[ChrisHager]

Sidewall says max load = 2403 lbs and max PSI = 44

BTW, my WJ is 2wd V8 SE

Wow, their recommendations seem too high. I'll run the numbers and report back tomorrow. My 50 psi on a heavy vehicle with 80 psi max seems kind of reasonable. They're trying to put you at max, which isn't what you want. Odd.

 

[ChrisHager]

It appears we have a conflict of interest between my calculations and what General Tire suggests...

This seems much too low. In fear of a bug in my program, I ran numbers for a WJ/tire combination that I know are correct. I was able to verify it is working properly.

I wouldn't inflate those tires to 42 PSI nor would I run 21. If I were you, I'd start around 32ish and adjust depending on their footprint. If they look low, fill them more. If you're running in the center of the tread, let some air out until you have a flat footprint.

 

[Eaallred]

I treat the side wall as a ratio. Been doing it for about 15 years now, and my tires skyway wear even all the way down to the wear bars

If the side wall says 2403lbs @ 44psi, if you have (for example) 1200 lbs on that tire, proper tire pressure would be 22psi. If you had 1800 lbs on that tire, you'd put the tire at 33psi.

Using that method, and just going by the GVWR in the door jamb (figure, set tires for max load) my 265/70r17 BFG KO2 with C load range came to about 28psi front, and 30psi rear. Rides super nice, still get high teens on gas milage, and read wear is even.

I'll still drop pressure to 12-15 psi in moab depending on the trail, but fir the street, I use the above method on everything I drive and it works great

 

[BuickNut]

One thing no one seems to be considering is the width tire vs. width wheel plus sidewall height. There is a lot to consider.

 

[Eaallred]

One thing no one seems to be considering is the width tire vs. width wheel plus sidewall height. There is a lot to consider.

I don't think that has any bearing as long as you run the recommended rim width range for the tire. It stays centered with the wheel. I see no connection personally