Been adjusting PSI on JLR

[Old Jeeper]

I'm fairly sure that MPG would increase at higher pressures. At, of course, the cost of diminishing other desirable characteristics.

You are correct, note I said Optimizes not maximizes. If you want max MPG then pump up those tires until they only wear in the center of the tread. The key is optimizing the whole package: Braking, traction, mpg, and finally safety. I have got the best contact patch for street driving. in and around the city. When I take a long trip in Interstate I add some psi to improve my mpg.

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[Old Jeeper]

I run 28 psi cold. Anything over that and the tires don't wear correctly. I would think 33 and 32, like your at would cause the tires to cup real bad. Did you do a chalk test or just basing the pressure off of ride quality?

That is a generalization. You need to treat tires as individuals, A lot depends upon the load range of the tire, the mfg and other factors. I don't the chalk test there are other approaches the provide a more defined answer. I like either the dust test and pics show that or the wet test, if you have flat driveway spray water on it and drive across it and give you the answer.

As for cupping, that is not a result of tire pressure but rather a weak or leaking shock is the cause of cupping.

Pic below is the result of the WET test, note the outer tread is dry while the inner is wet. This is on my F 450 dually truck. I adjust down to 70 psi city and 75 psi hwy.

 

[Old Jeeper]

Be aware that the weight of your Jeep impacts all of this. That makes boilerplate suggestions about tire pressure somewhat challenging.

Supposedly you can measure the size of your tire's contact patch (width times length in inches), multiply that by four (4 tires), and multiply that by your average tire pressure in PSI. That should, according to the math / science, give a decent estimate of the weight of your vehicle in pounds.

interesting, I have NEVER heard that, not disputing just never heard it. I need to try that sometime. Myself I am a CAT Scale man. I CAT scale all my vehicles as it gives axle weights not just one gross weight. I get the steering axle, drive axle, and trailer axle (if I have one attached) separately and a GVW.

 

[Old Jeeper]

I'm fairly sure that MPG would increase at higher pressures. At, of course, the cost of diminishing other desirable characteristics.

When I do the contact patch test, be it dust or wet I am at operating temp so I have been driving and its on a HOT tire.

The contact patch you want to optimize is at normal operating temperature and its that I am looking for.

 

[Ratbert]

interesting, I have NEVER heard that, not disputing just never heard it. I need to try that sometime. Myself I am a CAT Scale man. I CAT scale all my vehicles as it gives axle weights not just one gross weight. I get the steering axle, drive axle, and trailer axle (if I have one attached) separately and a GVW.

Yes, it's much easier (and more accurate) to simply go to a CAT scale. I did that when I brought it home from AEV in Michigan, then again after adding a crapload of gear.

Being aware of the math behind it is interesting though. It makes the results of doing something like increasing or decreasing tire pressure obvious and predictable.

 

[Old Jeeper]

Yes, it's much easier (and more accurate) to simply go to a CAT scale. I did that when I brought it home from AEV in Michigan, then again after adding a crapload of gear.

Being aware of the math behind it is interesting though. It makes the results of doing something like increasing or decreasing tire pressure obvious and predictable.

I think the off-road aspect of Jeeping has faded quite a bit. I think the reason why: Its a bit more than big tires and a lift. Those that pursue that line of reasoning are always broken on the trails. They throw on a set of 37s/39s and a 4+ lift and think they are going to be king of Moab. They go beyond the parameters of the Jeep they own and the results are generally quite expensive.

You got to know your Jeep and your personal limitations. You and your Jeep need to operate as 1 and meld together to the point you know you Jeep so well in the rocks (or what game you chose) that your Jeep is predictable. By the time I was running the 7+ trails I no longer used a spotter...my experience with spotters is spotters can't see spots on a Leapord. If you cannot drive you cannot spot.

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