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GCR & Oodnadatta Tyre Pressure Determining

Posted: June 29th, 2018, 12:01 pm
by jessehmn
Hey guys,

I'm new to the forum, so please correct me if I post this in the wrong section. I've used the search function but still can't find a real answer on my question.
I am fairly new to 4WDing and I'm going to do (part of) the Oodnadatta track and the Great Central Road from Yulara to Kalgoorlie in the second half of this month.
Now as both are unsealed (gravel) roads it seems more than logical to deflate the tyres a bit to reduce the risk of a flat. Though I am not sure what the tyre pressure should be.
As these tracks obviously will be different in roughness / condition, I reckon the tyre pressure for one another should differ. Is there a good way to determine when to de- or inflate the tyres a bit more?
I heard that the GCR from the WA border to Laverton in a way better condition than the NT part. Can I drive both parts with the same amount of PSI in my tyres or is it recommended to drive the WA part with a higher pressure than the NT?

Second one is the speed. Basic physics are that the bigger the contact point of the tyre with the ground is, the quicker it will heat up. What would be the max. km/h be to drive on deflated tyres?

My car is a Mitsubishi Pajero from 2000 with Hifly All Terrains.

Thanks heaps in advance!

Re: GCR & Oodnadatta Tyre Pressure Determining

Posted: July 3rd, 2018, 8:59 am
by MYCol14
You have sort of answered your own question. Road conditions are an influencing factor in determining tyre pressures. So in places where the road is badly corrugated you may want to run lower pressures/softer tyres so that the tyres absorb much of the shock from the varying road surface. How heavy a load you are carrying is another factor, e.g. as you suggest if you go too low in tyre pressures the tyres can heat up and fail (more so the heavier the load). Re top speed, it will vary depending on your tyre pressure. My experience is it won't be an issue for you on these roads if you are travelling at below 90 kph (which is recommended on dirt roads, some even suggest 80 kph max, which is a good idea if you are new to off the bitumen driving). You will soon feel if your tyres are too highly inflated on dirt/gravel roads as you/the vehicle will feel the shocks and vibrations as you hit a bump or corrugations.
As a general rule if I am running a fully loaded 4WD on the bitumen with say 44 p.s.i. in the rear tyres and 36 p.s.i. in the fronts, on the dirt I'd drop pressures down to 33-35 p.s.i. in the rear and 26-28 p.s.i. in the front and see how it goes. If the corrugations are a bit rough I then drop pressures down to 28-30 p.s.i. in the rear and 23-25 p.s.i. in the front. As you can see it is a trial and error thing, largely depending on road conditions and weight of loaded vehicle/weight on each axle. Hope this helps and hope you get a few replies.

Re: GCR & Oodnadatta Tyre Pressure Determining

Posted: July 5th, 2018, 1:19 pm
by jessehmn
Thanks heaps for your info MYCol14! I think the car will be pretty loaded with supplies, spare tyres and in total 3 people so will keep that in mind. Funny you've got different tyre pressures in front and rear, didn't know that's a thing. I definitely won't go faster than 80 kph. Hope it will all work out, but in any case I've got three spares with me. That should get me to the nearest town when I blow one I reckon haha. Thanks again!

Re: GCR & Oodnadatta Tyre Pressure Determining

Posted: July 5th, 2018, 6:52 pm
by Peter Aawen
Check out all the tyre pressure info that's already here by searching on the 4psi rule, & there's also a document floating around here somewhere that was put out as an easy guide for travellers by the late Adam Plate, a doc which reflects his experience with what pressures work for which type of vehicles from his years at the Pink Roadhouse, Oodnadatta. Adam's recommendations do end up being very close to those that the 4psi rule recommends, but they are certainly a bit easier to apply for those who can't be bothered checking their pressures more than once! :sillywink: If I can get the various links or images to upload on the cantankerous tablet that I'm using to post with atm, I will add them, but for now, you'll hafta use the search facility, sorry! :o

Now please bear in mind that the OPTIMUM tyre pressures for the tyres on YOUR vehicle as loaded by YOU and driven by YOU in the manner & at the speed YOU wish to drive at will very likely be a little different to the pressures etc that anyone else might come up with, simply because your driving style, braking, turning, etc and your load, the routes you choose, & even the vehicle & tyre brand or size that you choose means that tyre pressures are much more 'individual' than most think - there is NO single correct one size suits all tyre pressure, and those pressures printed on the tyre placard on modern vehicles are at best a fairly rudimentary compromise pressure often biased towards presenting the ride & handling 'feel & style' that the vehicle manufacturer wishes that vehicle to be recognised as, but even then that is IF & ONLY IF you stick with the OE tyre - as soon as you fit a replacement tyre &/or a different size or tread pattern, let alone a different brand or an LT tyre instead of P tyre, those figures on the tyre placard aren't even a 'best guess' & really only provide a common starting point for working out what is best for YOU & YOUR driving style, load, the road surfaces you drive on, etc, etc!!

Personally, my generally heavily laden GQ Patrol running 35's rarely required pressures higher than the high 20's/low 30's on the bitumen, dropping down to the low 20's on good dirt, and generally running around 15 psi but sometimes dipping a pound or two below 10 psi once we hit the real off road stuff!! But I checked my tyres & their pressures regularly, changed their pressures whenever the road surface changed significantly, & got my tyres checked & balanced frequently, as well as having the wheels aligned at least every 10,000 km, & I rarely got less than 100,000 km out of my tyres. YMMV! ;)