pathfinder replied:

my understanding is that sidewall fractures on rough roads are more likely to occur at high tyre pressures rather than low pressures, with some recommending pressures as low as 25psi for rough dirt roads. On bitumen 36psi plus should be fine depending on load.

ExplorOz Team - David replied:

Savas,We love this question (and in fact we are going to release a hot topic feature on tyres). We run our tyres on our heavy 80 series at 34PSI tar, 28PSI for every type of dirt/off road location. Touch wood we have not had any tyre failures for over 18months (since we reduced our driving presures). Yes as soon as we hit a bit or serious dirt the tyres come down. Previously we ran the tyres on the 38+ PSI ranges and we used to blow them (destroy/fracture) all the time.Our current recommendations come from the manufactures and not the retailers. Unfortunately however, every manufacture/tyre and vechicle seems to be different in it's requirements but rest assured reducing your preasure will reduce your stone fracture failures. Also if you have had no problems at 35 or so then do not change. With tyres and presures, the one solution fits all approach does not work.Good luck David

paul replied:

David

What sort of rubber then do you run on you 80 Series - BFG A/T's ?

andy replied:

Every time I have bought tyres from retail outlets I have been given quite different advice on tyre pressures from their staff. I called 3 tyre stores for the correct running pressures for my latest set of all terrains and they all gave me different figures. I am on my 3rd set of All Terrains and from my experience on correct tyre info take the advice of people that actually do trips in 4WD vehicles and have "real" experience such as the ones who use this forum. Andy.

By the way I run my 31x10.5x15 A/T's on my Hilux duel cab at 36 on road and reduce it to 18 on sand. 25 when in mud or dirt when loaded. I have never recieved a puncture to date off the bitumen with these pressures.

paul replied:

I have BFG's on my 90 Series. Tyre people put them on and said have between 38 and 42 depending on load or you will wear the outside edges down first thus reducing offroad grip of the tyres. After my next service at Toyota the techies let them down to 34. have posted this issue on the Overlander site and never really got a satisfying reply - ....

Will replied:

Savvas,

I have been running my 265/75 16 on my GU Patrol for 85000kms, 35psi on bitumen and 25 on dirt, not even a puncture yet.
Did W28631, Vic High Country several times and the Simpson and they are still OK.

Proves the point that the retailer is wrong...!!

Will

Cairns Offroad Training & Tours replied:

Most ppl run too much pressure in thier tyres in the mistaken belief they will have fewer punctures. In fact the opposite is true. If a tyre has too much pressure it is unable to conform to rough ground allowing a sharp rock or similar to punch into it, braking and grip also suffer markedly. If your tyre is run at the correct pressure it will conform to the road surface better, grip better and run at its correct temp thus increasing its life, your ride and comfort level also improve dramatically at the coreect pressure and your suspension has a much easier job. Tyre sidewall flex is designed in to become an active part of a vehicles suspension. I usually run my 31\10.5\15 tyres on my cruiser at 34lb cold I have just tried some new 32\11.50\15 tyres and due to thier heavy construction I am down to 30lb all round after dropping in 2 lb increments from 40lb. Tomorrow I will go back to 32 in the front and 30 rear as at 30 I lost a touch of steering precision. Generally I go as low as I can go without effecting my steering control, then I check my pressure after an hours quick run to make sure it has risen by no more than 4lb when hot or it would have been too low to start with. Offroad around 25 sand no lower than 15 or you run a real risk of rolling tyres off your rim. Hope this helps. Cheers Rob

kezza replied:

On road - check appropriate pressures for wide O/R tyres by smearing some silicon in a band across the tyre let it cure then drive 10ks or so see how the silicon wears off the tread do it twice 1/vehicle empty and 2/ vehicle full for long distances (obviously if the middle is disappearing 1st then tyre is overinflated for that weight - edges disappearing then underinflated.) Take notes, use common sense and adjust as necessary.
This method removes the debate on recommended pressures as tyre width, vehicle weight etc etc all vary so 30 psi in a light zook may be overinflated and 34 in a laiden patrol may be way under depending on the tyres.

Offroad you now have a baseline to work with eg 10 psi in a cruiser or patrol plain silly on a zook probably great.
happy bouncin,
kezza

gary replied:

If you think of your tyre as a balloon, and when it's blown up tight and you poke it with something sharp compared to when it is half blown up, you will notice that it takes a lot more effort to puncture it when it is half full.

mike replied:

I've used BFG A/T's - LT 235/85/R16's - run them highway 48-50 psi , work great with the 4psi test after about 30 mins driving . I'm now on second set on 92 MAV diesel no probs.-- 60,000 kms. out of first set. Let them down to 38 psi on dirt and - SLOW DOWN - to suit conditions. I have experimented with lower pressures on bitumen --highway and around town , but any less than 48psi feels like you're driving on marshmellows ! Hope this helps all you experts out there.