Tire Pressure?

[SafeAirOne]

I'm running 16" tubeless NATO Steel rims with 235-85-16 tires on my 109. Anyone running the same setup? If so, what are you using for a tire pressure?

I had the oil changed at one of those "Quickie-Lube" places recently (I know, I know...that's a whole different subject). When I checked the tire pressure the other day, I found they put 50psi in the tires. This surprised me, but I took a look and the tread contact area, and it actually looks pretty good. Wear pattern on the tires is even...

[109 Pretender]

Safe,
I'm running same size, same rig, and I run 50psi. I started w/35psi, but I found that Rover didn't corner well at all - tires seemed underpressured. Higher pressure cured that 'tire rolling under 'feeling. My Firestone Destination M/T's are rated to 85psi E - range. Footprint looks good @50 psi too. I ran my old tires @ 50 psi as well, never any wear problems. I think my rig weighs a lot - especially w/1/4 galv. skid plates and all the other stuff I bolted on...

cheers!

[Leslie]

Hmmm............

Now, mine's an 88", but.....

My tires could go up to 75psi cold, but, the book calls for 25psi, so I'm currently running 30psi.

However, I've noticed that, on a curve to the right, it feels like the left rear squats a little.... I wonder if I should bump up my psi.....

[greenmeanie]

Tyre pressure is something that is unique to every vehicle and tyre combination. Even those recommended pressures on the stickers on modern vehicles only really apply to the stock tyres as different makes and styles of tyre flex differently and on a machine such as a LR vehcile weight varies considerably.

Here's a trick to get it right:
1. Find a nice dry piece of flat concrete and line your truck up with the steering straight.
2. Apply chalk dust in a strip 2-3" wide across the width of the tyre.
3. Roll forward a few tyre revolutions, stop and inspect the chalk strip.
4. Do this for both front and rear to account for the different axle loading.

Looking at the chalk strip:
1. If the center is worn off then your pressure is too high.
2. If the outer edges are gone then your pressure is too low.
3. Even removal across the entire width shows correct pressure.

Some things to note are:
1. You need proper alignment for this to work.
2. Use this test when your vehicle is loaded as you intent to run it.
3. Your neighbours or people walkign by in the car park will think you have lost it far beyond just being an eccentric Rover owner.

[Leslie]

Tyre pressure is something that is unique to every vehicle and tyre combination. Even those recommended pressures on the stickers on modern vehicles only really apply to the stock tyres as different makes and styles of tyre flex differently and on a machine such as a LR vehcile weight varies considerably.

Here's a trick to get it right:
1. Find a nice dry piece of flat concrete and line your truck up with the steering straight.
2. Apply chalk dust in a strip 2-3" wide across the width of the tyre.
3. Roll forward a few tyre revolutions, stop and inspect the chalk strip.
4. Do this for both front and rear to account for the different axle loading.

Looking at the chalk strip:
1. If the center is worn off then your pressure is too high.
2. If the outer edges are gone then your pressure is too low.
3. Even removal across the entire width shows correct pressure.

Some things to note are:
1. You need proper alignment for this to work.
2. Use this test when your vehicle is loaded as you intent to run it.
3. Your neighbours or people walkign by in the car park will think you have lost it far beyond just being an eccentric Rover owner.


"Problem" w/ these XZL's is the sidewalls, being so dang strong, for an 88". Doesn't matter if I've got 20psi or 60psi in 'em, they look the same.... not like on my Sierra or the Disco... you can tell a visual difference in the sidewall at different psi's w/ them (or, even on the Impreza's street tires). I'd expect, if I did the chalk test, I'd tell no difference at a usable psi. I'm not gonna run 'em over 50psi, nor under 20.... I just need to figure out what's best.

I was on the low side, thinking it'd be more comfortable of a ride over bumps, but, maybe harder would be better for the roll....

[TedW]

235/85/16 Cooper ATR's. Soft top, parabolics, polybushes, SWB. Wicked comfy. No appreciable squish or body roll. Handles fine, IMO.

[greenmeanie]

"Problem" w/ these XZL's is the sidewalls, being so dang strong, for an 88". Doesn't matter if I've got 20psi or 60psi in 'em, they look the same....

I was on the low side, thinking it'd be more comfortable of a ride over bumps, but, maybe harder would be better for the roll....

I'm used to dealing with 10 ply bias construction bar grips on a 101. Like you say they show no deflection in the side wall unless totally flat. The thing is you are not interested in the look of the sidewall. That is for tyre kickers. You are interested in the contact patch of the tyre tread. Setting the correct pressure affects the contact patch even on the big military tyres.

The chalk trick does not provide a single tyre pressure but with multiple runs allows you to find the window of pressure for your setup. You can then vary the pressure within that window to play around with your ride feel.

You do bring up the other factor to consider here which is tyre load range and intended use. The XZl is like the bar grip where side wall strength and resistance to cuts is a big plus as is load range. These are not soft riding tyres.

[Leslie]

True, and, I didn't get them to be a street tire.... but, I do want them to be as liveable as possible while enroute from the house to the woods.....

[SafeAirOne]

Well, it looks as if I'll have to verify the tread contact pattern. My truck isn't nearly as kitted-out as Pretender's, so I suspect that his 50psi is probably OK while mine's a bit high.

Unfortunately, 90% of my driving is highway driving and my tires reflect this.:(

Thanks for everyone's input.

[Tim Smith]

Wow. I guess tire pressure really is different for every vehicle and tire.

I'm running BFG MT 33x10.5 15's on the lightweight and I generally tool around town at about 27 front, 23 rear. For extended highway trips I'll pump it up to 45 - 40 lbs. It seems to loose roadway grip at those pressures but for me the benefit is in top speed and mileage.

[yorker]

Wow. I guess tire pressure really is different for every vehicle and tire.

I'm running BFG MT 33x10.5 15's on the lightweight and I generally tool around town at about 27 front, 23 rear. For extended highway trips I'll pump it up to 45 - 40 lbs. It seems to loose roadway grip at those pressures but for me the benefit is in top speed and mileage.

haha yes well I think I have been running around on 14psi for a while in my 88" I aired down for an event last fall and never got around to refilling them. They are some old BFG bias plys though and 10 ply so the less air the better on an 88 imho... ;)

[Jeff Aronson]

Wow - 50 lbs? I've never run that much in my II-A 88"'s because I don't want to be pounded any more than necessary on the road. My tires are now 16" BF Goodrich AT M+S.

Just remember to reduce the pressure in all the tires substantially if you go off road or when the snow flies. At that pressure, unless you have a very soft tread, you'll not get much traction.

Jeff