Tire Pressure?

[Finlayforprez]

Hi Everyone,

I am just wondering if anyone deviates from the LR recommended tire pressure for front and back tires? Or, do you just go with what's recommended as far as tire fill?

I'm curious. Thanks!

 

[rostov]

I always go with recommended. There are many theories, especially for high performance tires.... but for normal conditions - just recommended, checked on cold tires. And not max pressure that is stated on the tire, but the pressure off the sticker of the car... just saying... 8)

 

[a517458]

42 front and back. 42 on front make the car handle sharper.

 

[Finlayforprez]

Thanks for the advice! I also wonder about tire pressure when going off-roading?

I only plan to do easy/moderate trails - nothing major. Do people recommend letting some air out of the tires? If so, how much?

 

[CaptainSpalding]

I do not recommend airing down with stock tires. There are two issues.

The 19" rims of the LR4 do not lend themselves well to off-roading. The problem is that with the stock 255/55R19 tires there's only about 5½ inches of sidewall. Airing down would only reduce that slim margin. Between the reduced sidewall and the lower pressure, the aluminum rims are much more vulnerable to damage. Better off-roading tires have a lot of sidewall.

And about that sidewall: proper off-roading tires like BFG All-terrains or Goodyear MTRs have triple-ply reinforced sidewalls, so that when the tires are aired down and the vehicle is actually riding on the sidewalls, the sidewall portion is less easily cut or punctured than would be the case with unreinforced sidewalls.

 

[Finlayforprez]

I do not recommend airing down with stock tires. There are two issues.

The 19" rims of the LR4 do not lend themselves well to off-roading. The problem is that with the stock 255/55R19 tires there's only about 5½ inches of sidewall. Airing down would only reduce that slim margin. Between the reduced sidewall and the lower pressure, the aluminum rims are much more vulnerable to damage. Better off-roading tires have a lot of sidewall.

And about that sidewall: proper off-roading tires like BFG All-terrains or Goodyear MTRs have triple-ply reinforced sidewalls, so that when the tires are aired down and the vehicle is actually riding on the sidewalls, the sidewall portion is less easily cut or punctured than would be the case with unreinforced sidewalls.

Hello CaptainSpalding,

Thanks so much for the great information. I suspected that and had discussed this previously with blackforestham from the list. At this time, I am only planning very easy/moderate off-roading with no major sharp rocks or the like (mostly just sand, minor ruts, and some puddles). Thus, I decided to keep my stock tires and change them later if needed.

So, I guess if I am going to keep my stocks for now, it sounds like it's best to make sure they are properly aired up when doing this "light" off-roading. If I get into it more and find I am having issues with my tires, I'll cross that bridge later and dish out the money for some good on-road / off-road tires. For now, I think the stocks are fine for what I plan to do off-roading wise. I do not want to compromise on-road performance because that's where I spend 98% of my driving time.

One last question CaptainSpalding, some folks on the forum go with 42psi front and rear tires, while others go with the manufacturer's recommendations - what is your opinion on this - what do you do?

Thanks a lot!

Regards, David

 

[alexcorral]

David,

Check out the video I posted of a Discovery 4 in australia doing some tough off-roading on street tires. It is much more than what you're planning and it handled the stuff with no problems.

If you are in the sand and you get stuck you can let some air out and it will help you getting out. Sand will not ruin your tires. Also, plan on carrying a 12V inflator in the truck to air up again after letting air out.

 

[ThePecker]

I do not recommend airing down with stock tires. There are two issues.

The 19" rims of the LR4 do not lend themselves well to off-roading. The problem is that with the stock 255/55R19 tires there's only about 5½ inches of sidewall. Airing down would only reduce that slim margin. Between the reduced sidewall and the lower pressure, the aluminum rims are much more vulnerable to damage. Better off-roading tires have a lot of sidewall.

And about that sidewall: proper off-roading tires like BFG All-terrains or Goodyear MTRs have triple-ply reinforced sidewalls, so that when the tires are aired down and the vehicle is actually riding on the sidewalls, the sidewall portion is less easily cut or punctured than would be the case with unreinforced sidewalls.

In deep sand or snow you probably would need to pressure down, and hopefully you won't have to worry about damaging your rims there. You can probably go down to 20 psi or so, but I would reinflate soon after. Obviously consider vehicle weight and what tire you're running

 

[CaptainSpalding]

. . . some folks on the forum go with 42psi front and rear tires, while others go with the manufacturer's recommendations - what is your opinion on this - what do you do?

I tend to go with the manufacturer's recommendation, but not always.

There are two reasons one might want to stray from the manufacturer's recommended tire pressure. Reason 1: handling. I don't drive my high-profile 4WD vehicle in such a manner that any increase in handling from varying the tire pressure a couple of p.s.i. one way or another comes into play. So while reason 1 might apply to other vehicles, it doesn't apply to my LR4.

Reason 2: tread wear. In your mind's eye imagine the tire in cross-section view. At normal pressure, with the vehicle unloaded and the tires warm, the tread should be sitting flat on the ground with almost even pressure all the way across from inboard to outboard. Next, imagine that we over-pressurize the tires. Now the section will be rounder. The edges of the tread may even lift slightly off the ground. More weight is being placed on the center of the tread, and more wear will occur there. We don't want that. Next, let's assume the tires are under-inflated. The sidewalls will have a tendency to bow outwards ever so slightly, and putting more weight on the edges of the tread and tending to lift the center of the tread. So wear will be concentrated on the edges of the tread.

What we want is for the wear to happen evenly (and hopefully slowly) across the entire width of the tread. Now imagine that you are going on a long road trip with the whole family, your Great Dane, and lots and lots of luggage. On another vehicle, the rear end would be sagging a little from the extra weight, but our nifty LR4s have computer controlled air suspension that automatically compensates. And that's awesome. But the extra load might give our tires the cross section of an underinflated tire. One might consider increasing the rear tire pressure a bit. Don't exceed the maximum recommended pressure under any circumstance, of course.

Those are my thoughts. YMMV.

 

[CaptainSpalding]

In deep sand or snow you probably would need to pressure down, and hopefully you won't have to worry about damaging your rims there. You can probably go down to 20 psi or so, but I would reinflate soon after. Obviously consider vehicle weight and what tire you're running

Sorry, but I disagree. Sand and snow want big fat cushy tires to help you "float" on the surface instead of digging in. Airing down the tires increases their contact patch or footprint on the soft surface and helps prevent digging in. The sidewalls of the LR4s stock tires are so skinny that airing down the tires wouldn't give much, if any, benefit of an increased footprint, but it would increase risk of damage to the rims.

Check out the video I posted of a Discovery 4 in australia doing some tough off-roading on street tires. It is much more than what you're planning and it handled the stuff with no problems.

If you are in the sand and you get stuck you can let some air out and it will help you getting out. Sand will not ruin your tires. Also, plan on carrying a 12V inflator in the truck to air up again after letting air out.

Alex, I loved that video! Thanks so much for posting it. I wouldn't say that the LR4 handled the obstacles with "no problems". I seem to remember a winch in there somewhere The Land Rover traction control allowed the LR4 to perform adequately in spite of having terrible wheels and tires for off-roading. I don't think you all realize how terribly hamstrung the LR4 is because of its wheels and tires.

Here's a rather long-winded armchair analysis. Take it for what it's worth.

The most capable off road vehicles have large diameter tires with small diameter wheels and lots of sidewall and some beefy lugs at the edges of the tread. They also have manually actuated locking differentials for traction control in iffy conditions. Part time 4WD trucks will need 2 locking diffs. Full time 4WD trucks need a third locker because there's an extra diff in the transfer case. The problem with locking differentials is that if they are improperly used they can cause damage to the driveline. Using them properly requires some education, just as with many aspects of off-road driving.

Land Rover is trying to give us a short cut to off-road driving without our having to educate ourselves. This is nice in a way, but ultimately they do a disservice to us and themselves, because the vehicles they produce today are less capable than they could be.

There are automatic locking diffs out there, but they are a little quirky. They make noises at odd times on the street and can be a little squirrely. It's no wonder that Land Rover didn't opt for them, because for the uninitiated and those who never intend to take their glam-mobile off road they would be a constant annoyance. Manually actuated lockers are superior but as I said they require training to ensure that the driveline isn't damaged.

So enter the ABS-based traction control system. Let it be said up front that if building the most capable off road vehicle is the goal, ABS traction control is definitely a compromise. It's benefit is that it can be made automatic. However, it does add considerable extra expense to the vehicle. And if the vehicle is acutally driven off-road then brake component wear is accelerated. The complexity of the system means that overall reliability suffers.

One specific problem with ABS traction control is that if it is used in a rigorous manner, the brake fluid will boil. That's bad.

It really sucks that we are stuck with such large diameter wheels, because it prevents us from using proper off road tires that have a nice generous sidewall. The limiting factor is the really, really huge brake rotors that limit us to enormous rims. I've asked myself why Land Rover would do this, and I can only offer a guess. If anyone tells you that the rotors have to be that big because the LR4 is so heavy don't believe them, because it's a huge load. Look at the Mercedes G-Wagen. It's as heavy or heavier than the LR4. It has brake rotors small enough to accommodate 16 inch wheels, and it stops just fine. The G-Wagen also has 3 locking diffs from the factory.

I suggest that Land Rover uses such large rotors because with the greater diameter of the rotor, the calipers don't have to work so hard to stop the vehicle. That means that the pressures and temperatures within the brake system stay lower, and the ABS system and brake fluid don't cook themselves as easily under rigorous off-road use. If this is Land Rover's rationale, I understand it, but I don't like it much. On the other hand, I could be totally off base. It could be that the LR4 has such stupidly huge rotors because those are the rotors that are used on Jaguars, and it's just cheaper to use the same thing.

In any case, those of us who really want to wheel are limited by the tire and wheel size of our LR4s.

Whew! Sorry for the rant.