Goodyear Wrangler At'R

The max pressure is usually marked on the side wall.

Rod,

The more pressure you put into a tyre, the less it heats up.

Cheers,

Jim.

Rod
You did not state your tyre size which makes a big difference.
Yes the max weight and pressure is usually shown on the sidewall .
EG. My 265/75/16 Wrangler ATs have 1250kg@ 44psi shown on the sidewall.
Wranglers do bag out more than some other brands which is normal.

The problem is that Wrangler ATR are not light truck and shouldn't be used for a caravan. Which is why you are getting so much side wall flex. Who recommended them for a van?

Secondly you will find the max pressure stamped on the tyre also giving the max payload for that pressure.

I run 4WD Light Truck HT on my van at 50 PSI. The more air the less heat is generated in the tyre from side wall flex, etc. Only dropped them to 40 PSI when I travelled the Birdsville Track becaue of the gibbers with no damage.

I have had Wrangler ATR on my Prado since late 2005 and rate them as a 4WD tyre. 100% on the Cooper AT crap I had before.

rredbeak,

From what you're saying about baggy sidewalls at 40 psi I take it your Roadstar a single axle van?

If so at 2 tonne the tyres should be Light Truck with a cold PSI of 50.

Running ordinary tyres on a single axle van at cold psi of 40 will cause a lot of flexing and heat buildup and you will also notice that the van will move around a bit under tow due to the flexibility of the tyre. You will also run the risk of a blow out with excessive heat build up.

If your van is dual axle @ 2 tonne and they are not light truck tyres you will probably get away with ordinary tyres as the load is generally spread evenly over the 4 tyres assuming your axles are on simplicity suspension or the rocker type. Each tyre would generally be carrying a load of 500kg.

However even under these circumstances I would be using LT tyresas they are more robust.

The best test is the 4lb rule, if the tyres are gaining more than 4lb @ their max cold pressure marked of the tyre's sidewall then they a would not be the correct tyre for their application as they would be gaining too much heat.

Apart from the sidewall,

there is another way to do it, and this way gives you the exact air pressure for any tyre under any given load.

Now heres the catch.... I cant remember it...lol

but its called the Pirelli principle, and is based on a hot n cold pressure.

you inflate cold to x psi, then drive so far n check it, and its not meant to go up more than a certain amount or you need more air, and if not gone up enough you need to let some out.

I'm sure with a bit of googling you would find it.

Its quite simple formula, but also quite spot on, lets you find your own unique settings for your rig.

Ron