The real tyre pressure.

Wayne,

First let me say that I think you are right. The accuracy of portable tyre pressure gauges is questionable. I only carry 1. I figure it is at least consistent so all my tyres will be at the same pressure even if it is not the pressure actually displayed on the gauge.

There are a lot of variables when it comes to driving conditions, gravel is different to clay, is different to road base, or sandstone, or limestone and sand varies from place to place, season to season and with moisture content.

I have a system which gives me starting points, so on sand I always start at about 18psi on my gauge. If that is too soft or too hard I make a judgement call as to how much to adjust it by. Sometimes it will be 2psi sometimes more. I generally get it pretty right with the second adjustment or maybe I just make do.

When I did the Simpson Desert I started at 18psi at Dalhousie but by the time I got over Big Red I was down to about 13.

The thing I take from this is that there are no rules. 4 wheel driving is an art not a science.

Duncs

G'day Wayne,this is a bit of a mine field as to what is the right pressures & gauge as the gauges all tell lies in my investigation.I use the one only to set & check my pressure,i will pump them up with the gauge on the end of the hose then check with the pocket one.

Now the set tyre pressure for different lanscpes for me is a different ball game from what most others on here may well use,as i runin my tyres when fully loaded 75psi the max on the tyre is 80psi so 5psi below should be ok if the pressure builds up due to road conditions (black top) mainly,but what i should run them for sand,mud is the Q.

When i got the truck 4 & half yrs ago went to Moreton Is. to too loaded then i had 60psi & went down to about 40 or 50psi cant remember for sure but still had a little trouble (one big) hole (u missed this 1 Trevor R) got a lit stuck & managed to get out ok though.So iguess a little trial & error for me to get used to what works & what don't.

Trip up to the cape earlier this yr i did not even let them down & not even a problem (no sand work) on the beaches though.

Cheers,


Bob.

Wayne (NSW)

This continues to be an interesting subject although I ma by no means an expert.

For some time now I have been running tyre pressure monitors which also gives me tyre temp. Or more to the point, air temp in the casing.
These are internaly mounted on the rims. Its interesting to see the change in tyre pressure as the speed changes and the sun moves from one side of the vehicle to the other.

regards

Hi Wayne,
Tyre guages are a bit of a pain and very hard to test your personal one against the garage ones as they get knocked around and most are not accurate.
Even if your guage is out by a couple of pound I think as long as your tyres are uniform in pressure then you should get even tyre wear and the pressure is within what you think you should be on.

As for driving on sand the only way you can get your tyres to the "right" pressure, albeit your guage maybe out is something called flotation.
Flotation is where you can drive on sand and your fourby coming to a rolling stop without using brakes.

In WA our beaches vary from one beach to another. you can drive on 20lb on some and down south, the beaches around Peaceful Bay I maybe down to 12-15lb as the sand seems to be bottomless and then you have to be careful how you turn so as not to roll tyres off the rims.
When I drive onto a beach I drop my tyres down to about 25, hop into the fourby and put it into gear drive off and then take my foot off the accelerator and if it stops suddenly without braking then I let another few pounds out until I can take my foot off and the fourby comes to a rolling stop.

I did the stock route on 22 pound according to my tyre pressure guage.
I drive a patrol and on bitumen I run on 40 (according to my guage) and gravel with corrugations on 30.
Remember you must always check tyre pressures when they are cold as when hot with heat build up you could be 4-6lb higher according to the specialists.
Nugget

I understand why etc. letting tyre pressures up/down. But what about the trailer? I have a 2005 Kimberley Kamper and (at this stage) have never had it off road (sob sob). What do others let their trailer tyre pressures down to?

Malcolm

I have 2 of those little stick type that differ by 4 PSI
I take the average and also do a check against service station's gauges from time to time. As long as they always remain 4 PSI apart - I then know where they read - relative to the average of a large number of other guages.

Easy - dont bother 'airing down' unless in sand. All the rest is un-necessary in my experience unless climbing lots of steep rocky tracks, which is rare for me.

Guy's
Try this thread

This is what we found, on our recent trip

ThreadID: 71971
Posted: 2 Sep 09 12:59

Cheers
Bucky

Wheelers
I once took a shorty to Fraser and chose some nice new 32/11r/15 bridgestones thinking they are wide and will float better.....wrong......all the busses up there have widened splitties so they can run larger diameter fairley narrow tubed tyres at lower pressures without the tyre parting from the bead of the rim. Doing it this way minimises how much sand the motor has to push each tyre through, (narrower x4) larger diameter increases the footprint length (front to back of tyre) at a given pressure over a smaller diameter tyre, and the larger circumference of the tyre means the leading edge rolls over the sand better without causing a wave of sand to build up infront of each tyre.
By the end of the trip, i had aired my 11r tyres down to 11 psi. next time i went, i took 255x85x16 or 33x10r and drove everywhere on 18 psi
Andrew