Hi Gary and Kerry.
It is extraordinary to me that there is so much confusion and variation in personal opinion when it comes to tyre pressures. It is even more dramatic when the subject of 'off road' is included. Even 'professionals' who sell and fit tyres often can't agree and give conflicting advise.
It should not be that hard.

Now for my view......

The only 'authority' on a tyre is the manufacturer of that tyre.
Every tyre has the maximum load that it is designed for and the maximum pressure (for that load) moulded into the side of the tyre. These are for highway speeds.

Tyres are designed to be a particular 'shape' on the road.
If a tyre is under-inflated, the side walls flex too much and they will overheat an fail violently.
If over-inflated, contact with the road will be reduced, braking and handling will be poor, and the wear pattern will not be correct. Many people seriously over inflate their tyres and use all sorts of arguements to justify their position

You MUST know the actual load that the tyre is carrying to get the pressure correct (front and back will be different, and maybe even left and right might not be the same).

Good tyre manufacturers actually publish load/speed/pressure data for their tyres, so the best advise is to get that from them. If you can't do that, my 'rule of thumb' is to proportion the data printed on the tyre for the actual load. In other words (as an example), if the tyre is marked "MAX LOAD SINGLE 2000kg at 60psi" and the actual load is 1500kg (75% of the maximim) then I would use 45psi (75% of the quoted pressure).
All pressures should be measured when the tyre is cold (again, this will be stated on the tyre). The pressure increases quite a lot as the tyre warms up on the road, and even more if it is in the sun.

I am sure many people will give you advise that conflicts with the above. If you are unsure, get the data from the MANUFACTURER in WRITING, and ignore opinion.

Cheers,
Peter.

Basil Faulty wrote:

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Firstly I'd like to know what you think of the Adria....
Tyre pressures yes a pandoras box here. One of my sons is a registered Tyre fitter and he says the rule of thumb is to use the reccomended pressure then drive/tow at higway speeds for 15 mins or so and measure the pressure again, if it has gone up by more than 4-5 PSI then put more air in abot 5psi at a time untill you get a pressure rise of no more than 3 psi.

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The Adria,
We purchased second hand, first registered Jan07 and we bought Mar08. The previous owners traded it for a bigger van (confirmed with them via phone whilst they were in Broome) at the same price it was traded.

I have copped a fair bit of flack about it, not suitable for australian conditions,won't last, difficulty getting parts, insurance companies won't insure etc. None of which I have found to be factual.

We looked for about 9 months at many different vans, went to caravan shows,and read many reviews on different makes before making a decision.

The thing that won us over was the feeling of space, other vans that we looked at didn't have that feeling.
Also the weight 2000Kg for a 23' van ain't bad.

SWMBO liked the amount of storage and the internal finish.

It tows like a dream behind my terracan (2500Kg towing capacity) and I get 15L/100Km on the open road.

Have only done short trips so far (300K's from home ) but am planning to take 4 months long service mid january.

I have been told about the 4PSI test and that seems to be the best way of doing it.

There is another member on here who has exactly the same rig as me but I can't rember her name.

 

-- Edited by Gary and Kerry at 19:25, 2008-08-23

-- Edited by Gary and Kerry at 19:31, 2008-08-23

tyre manufacturers have very little idea of the purpose that the tyre will be put towards (trailer, caravan, camper trailer or 4wd) a rule of thumb is 45psi on road, 35 on dirt and 25 on really rough stuff and stones, remember to replace the air when back on highway, high pressure will destroy the tyre on stones and low pressure will destroy the tyre on bitumen

exactly right as far as weight and applications are involved, I have seen these tyres on spray units and also on blow seeders, on a super spreader we used to run them at 60psi, and off road trailers weighing in at less than a tonne 45psi so the side of the tyre pressure rule is way out, if you have higher than 45 in a spray unit tyre, one cannot control the spray arms ( I know because I have operated many of them) blow seeders are different again about 55psi rules here as it must carry the weight and "bight " the soil for traction, we have a trailer that does nothing but cart the dogs around probably about 20 psi in there because no weight involved been on for donkeys years, our diesel cart runs coopers, pressures are at 55, tyre manufacturers have a limited idea of what they design the tyre for, they have no idea what the end use will be, for example we used them on the farm to make up a drafting winch to bring in logs, and a recovery sled to drag the old truck out of the dam (wont say who put it there in the first place) I am talking typical pressures, if you are doing anything outside the manufacturers manefesto (and in australia that is in most cases the norm) then that must be taken in to account, the test grounds that these tyres are proven on, in most cases, are not even in australia and have no idea of australian conditions, the pressures I quoted were from drivers that I talk to who are out there and doing it all the time, I also spend a bit of time working as a fitter (cash under the counter) at a workshop, that a mate of mine owns, he also tyre fits by the way, happens to specialise in off road tyres,which in itself is a misnomour, bit of a hobby of ours, we often go away together ,so just a bit of experience talking, not fictional writing, I have seen these tyres everywhere from suzuki lightweights to ford f350s, how can the rule of one pressure suits all apply,  it cant and it doesnt, I experiment on an average given from manufacturers until I get the crown of my tyre running square, currently on my camper it is 60psi in the rear and 40 front, it performs perfectly at these rates, generally if your tyre is standing "straight" not too much side bulge at normal running temperature and normal weight then the pressure is not far out, rule of thumb is all we have, as applications change. of course you do realise that if the expected ambient temperature is to exceed 32c then you should deflate your tyre by a minimum of 3psi if driving more than 50 kms and if you are exceeding 100 kph then you should increase pressure by 5psi, if you are exceeding the average expected tyre bearing weight by more than 100 kgs you should also increase the pressure but then you must reduce the pressure by the ambient temperature divided by the weight carried times the distance travelled, this of course is assuming that you are the only one that knows the correct pressure for YOUR vehicle at the time of inflation divided by the overnight temperature expected in your region,  all that is of course with the greatest of respect, Oh I also neglected to say that I belong to the south australian branch of the australian off roaders association, so yes I have a teensy bit of knowledge on this and many other subjects, I just dont brag about them,  not counting industry, 92% of off road vehicles never leave the road, of the 8% remaining 3% do not tow, so that leaves 5% that actually tow and go off road, out of that 5% I dont include farmers so the numbers are insignificantly small, tyre manufacturers figures given to us, not mine, and not found on any website, the tyre manufacturers are in the business of selling tyres, who do you think they are going to aim the tyres at, it is of course the "toorak tractor brigade" mums taking kids to school and shopping, also dads dreaming of driving in the desert, so the towing and off roading, as told to us by a reputable distribution salesperson, is not the norm he is the exception and therefore not really of "significant importance" to tyre manufactureres, it is stated in all tyre recomendation charts all over our fitting station that "if it is wearing in the centre then the tyre is over inflated, if wearing on the shoulders then tyre is under inflated, remedy, inflate or deflate as required" that was placed there by a leading tyre manufacturer, whom I will not name because I am not that rich, lot of know alls in this field and a lot of bulldust as well, check 1,000 vehicles at any time, 999 wil be incorrect for the position they are in, and if you check your tyres at a busy station when the compressor is also used to pressurise the fuel pumps then you do realise that the air that you are placing in your tyres will be hot from the compresser and when you take your vehicle home and the air cools down it is immediately incorrect, specific manufacturers tyre pressures, in the industry we laugh at those people who spout that dribble, dangerous, bull****, rule of thumb is all we have, just one other little titbit to further your limited knowledge on this subject, if a tyre comes in to us that has prematurely erupted or failed, we must make a quick note of why it has done so, if it is on a four wheel drive and that vehicle has been towing an average caravan for any great distance or ventured off road for any reasonable time, then the note will be T.A. or in laymans terms TYRE ABUSE   the same as the drongoe out there chucking blackies everywhere, these notes are studied by the distributers and colated back to headquarters and assesed, where they are duly dismissed as minor infringements of the tyre warranty, the company also considers under inflation as t.a. ( deflating the tyre for driving in sandy conditions), any deflation of any tyre under a reasonable pressure will do great harm to the walls of that tyre, many theories on tyre inflation, the moulded pressure rating to weight is a guide only, a starting point if you will, the actual pressure you hang on to  is very rubbery, the old adage still applies, wear in the middle more pressure needed, wear on the shoulders reduce pressure, the companies will have all sorts of stuff on their website and will deny all knowledge of that to which I speak (and defend it vigorously through the court, thats why I wont mention names or show documentation, but I do have it by the bundles) but the information that I supply is gospel and will be debated by fools forever more, but ask your tyre fitter about the pressure for your vehicle next time, he will say "oh hell mate, I reckon about 45psi would do ya" and that is what we all do estimate and adjust accordingly

-- Edited by dave06 at 14:19, 2008-08-30

-- Edited by dave06 at 11:43, 2008-08-31

first up I would like to apoligise to the forum, I misunderstood the question, I thought it was about the tyre pressure of the tow vehicle and that is why I locked on to that,  the caravan tyres are of course light truck, but the numbers are still basically the same, THERES A LOT OF DRIBBLE FLOATING AROUND ABOUT TYRE PRESSURES, I replaced three sets of "OFF ROADERS"  two sets on caravans weighing 1000kgs this morning and set them up with the "average 45psi" to which I stated "she'll be right mate, knowing full well that it wont be, but what can we do, we must start somewhere, if you take the percentage of weight to pressure theory sprouted before, then I would have put 22.5 psi in there and that is WAYYYY out, makes one wonder how many sets did the other "expert" replace, good job my mate has his computer in the office so at least I can still keep in contact with the forum, let us know what the specialists say, and when you get the email would you send a copy direct to me, I would love to show it to my boss it will make for interesting reading and I am sure he would love to have a look, also our distributer would love it too, I pretty much know the standard answer but we will see, we may be surprised. meanwhile check this site out http://www.bridgestone.com.au/tyres/passenger/care/pressure.aspx  it gives a little insight as to what I am getting at, it is not the tyre that determines the pressure it is the vehicle and the way it is driven plus weight,  note how they keep reiterating about everything being "cold" but dont state how cold, this gives an insight in to the thought process of tyre manufacturers, I could give you a sales link, but they would sue the pants off me

-- Edited by dave06 at 20:05, 2008-09-01

-- Edited by dave06 at 21:58, 2008-09-01

yep thats about as close as you will get to a "specific" tyre pressure, thanks for posting, have sent it on to our distributer also in adelaide and he agrees, but states it could do with a bit more pressure. did you have a look at what the manufacturer requires for the van, I think you will find it is different again

Just back from weekend at Mannum. Set pressures as recomended above and found the ride a lot more comfortable. Also fuel economy was slightly better than previous trips of similar length.