Tyre Pressure

The manual is a good place to start.
I usuually check pressures cold in the morning when travelling, just looking for any drops and possible tyre problems.
Check them again at lunch time, or when airing down, so the hot/cold difference soon appears. Usually about 4 to 6 psi, depending on speed being run and road conditions.
You need to find pressures to suit yourself and your car.
Suggest letting down maybe 10 to 15% to start with for sand and corrugations.
Softer for sand. (Suggest 18 minimum for very soft sand, 15 in a dire situation, and no sharp turns.)
Keep letting them down and checking temperatures with your hand as you go.
Softer tyres generate more heat, and wear more. Higher speed generates more heat.
So doing 100 on bitumen could be the same as doing 70 on dirt tracks with 5 to 8 psi less pressure.
Softer tyres also bulge more, so side wall damage on tracks needs to be considered. Some say softer tyres are also harder to puncture, since they flex more easily around the object.

What sort of temperatures are you getting now on bitumen? Check as soon as you stop. That will give you a place to start.
It's all about building up experience and getting to know your vehicle.

Hi Red up

For corrugations your generally looking for a slight pressure drop - 10%

For sand your looking for bigger footprint which requires noticeable bagging of tyres - 18psi is a good start point

The pressure required is the same for warm and cold tyres - it just that if you adjust them cold then they will go up by around 4 psi when warm., so have to take into account.

Note -speed should be dropped in both cases else cold to warm increase will increase to 6psi or more and tyres will be overheated.

Robin Miller

You are going to get some different opinions on this. The suggestions above are different to what I do but along the same lines.

I drive a GU Patrol and set off from home with about 40psi all round.

When I turn onto the dirt, formed raod with corrugations, I usually drop pressures by about 25% that is to about 30psi. When in sand I drop by about 50% from my starting point , that is to about 20psi.

These are guidelines only and it varies depending on a whole bunch of factors. Road conditions, speed, vehicle load, or just how it feels.

Remember speed goes with pressure. The less pressure the less speed. Road conditions will generally dictate this but some people think they can march on regardless.

I travelled to Steep Point with my brother who was driving a Liberty Sports Wagon. In the soft dunes he ran 18psi and said that felt great. The Subie was certainly quick over the dunes and he could stop and start in places I wouldn't have dreamed of.

Duncs

best check on tyre pressure is to run them at your nominated pressures for about 100kms then check pressures again should be within 5psi of your starting pressure

Hi, red up
My Outback used to run well at 28-30 on rocks and corrigations & 18 in sand dropping to 13-15 in very soft sand (no sudden turns at this pressure) on Cooper Lifeline tyres, this rule of thumb served me well for 4 years with NEVER a recovery in the rough, In fact I recovered an Xtrail from Stockton once.

Colin