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A real dumb question, but what pressure would you recommend for Cooper STTs 31x10.5x15? I can check what they are at the moment (will do tomorrow), but no idea if that's good or not.
The standard factory pressures are a good place to start. There are also a couple of alternative ways to get somewhere near. On a clean flat surface rub chalk over thr entire width of a section of the tyre, then gently drive forward to leave a chalk mark on the ground. You can then examine how much of the tyre is in contact with the ground and how, it should be a nice uniform impression of the tread over the full width of the tyre. Alternatively you can use mathematics. The tyre will have a maximum load at a given pressure written embossed on the sidewall, the vin plate will have the maximum permitted axle weights front and rear. Divide the pressure on the tyre by the maximum load and you get the pressure per kg multiply that by half the maximum axle weight (2 tyre per axle) and you get the psi per tyre. Thats for road use off road and in certain situations much lower pressures can be used to keep you moving it depends on how serious the terrain is.
Temeraire (2018 quasar grey automatic)
One of the last 200ish of the gen3s, probably.
Bellerophon (2024 grello van daily
ADOS Attention Deficit Ooooh Shiny!
You've got nearly twice the footprint of the original tyres, so you can get away with very low pressures. Have a play and see what feels right. You'll have an uncomfortable time if they are too high!
Ive got a set of the cooper STTs on order in 31", how do you find the gearing with them and the rocklobster box? Also what ratios are in the rocklobster?
I run the 235's currently on at 20 road, 15 offroad and that seems a decent balance between comfort and grip, 31" could be even lower, but could make for sloppy handling on the road
J999 MNY, ULYSSES M18 VVT with ITB's Dyno tested at 130hp
I don't have much to compare it to, having only test driven a regular Jimny last week before this one to see what it was like. Having said that, the gearing seems better on this one. I have no idea about the ratios - the rocklobster was fitted by the previous owner to the guy I bought it off.
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Larger the tire, less air needed. 
