Tyre pressure

[Tig]

What tyre pressure would you suggest for a Discovery running 235/85/16's please?

[cardiff_gareth]

I run 245/70's which are 28 front and 36 rear but I'm gonna try them on 30 front and 38 rear  

[glaggs]

I run 245/70's which are 28 front and 36 rear but I'm gonna try them on 30 front and 38 rear  

Why?

If running bigger tyres then a lower pressure than std is usually best. Its air mass that supports the vehicle weight. The same mass of air in a larger space gives lower pressure. Having said that the type of use can mean a change of pressure ie constant high speed - increase slightly; larger load/weight - increase slightly. Higher pressure can give better mpg but taken too far will dangerously reduce grip. Having said that, 245/70's aren't significantly larger so std recommended pressure should be close to OK.

[cardiff_gareth]

I ran them at lower pressures and they were nearly running on the side walls so they were increased  

[Range Rover Blues]

Wider tyres will tend to look flat anyway, especially road biased ones that aren't as stiff.

I'd stick with the handbook settings for now.  Larger tyres tend not to like being inflated to the same pressure when fully loaded, the tread is more flexible and suffers from uneven wear.

But tyres work by the car hanging from the chords in the rubber, a bit like a spoked wheel, the pressure is secondary to that and not directly related to how much the car weighs.

[glaggs]

Would agree with all but the last statement.

Tyre stiffness can influence the way a tyre handles under external forces but air mass in the tyre is of primary importance as it controls tyre (and therefore rubber) temperature as well as maintaining shape and therefor controls the amount of grip the rubber has. The tyre will have been designed to give an optimum grip/ware rate at a set temp range. This is controlled by air in the tyre. A tyre run with too little pressure runs too hot, too much it runs too cold. But when you put larger tyres on they can handle a lower pressure to give the same temp. The tyre construction does also influence the temp caracteristics of the tyre but as a user the only adjustment you have is the pressure.

[cardiff_gareth]

so what does it mean then when the rear n/s tyre has a wear band on the tyre wall where it has rubbed on the road :?
That was running at 36psi :?

[glaggs]

Without having the chance to inspect the tyre and fitting its hard to comment, but a correctly fitted tyre run at manufacturers recommended pressure shouldn't show wear on the side wall. Either the tyre is faulty, it has been incorrectly fitted or someone uses the tyre as a guide for finding the curb. 2psi wouldn't realy be enough to make that much difference on tyre deformation. If you've got wear on the side wall the tyre would have to have been run at less than 10 psi, I wold check to make sure it isn't catching somewhere or that someone isn't runing the tyre against the curb.

[Range Rover Blues]

Would agree with all but the last statement.

Only going on what the engineers from Avon told me :?