tyre pressures on road

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Originally Posted by Finly Owner

Some can take 60 psi with no heat probs or any distorion probs. Check the rating on sidewall.

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That is right on the nose Tim. I have unfortunately got Goodyear Muds and run them at they're max of 35 on road (noisy as all f@#k). BFG AT's when I was in the tyre game we ran at 45 on road. I had a customer who had BFG MT's that lasted 110,000. Unbelievable but true. He ran them at 45 rear with load and 40 front (he had 6 wheels rotated every 10,00 km's). But generally run what the sidewall say's in a wagon. In a ute or shorty run 5 pound less than what sidewall say's if unloaded. Just a hint BFG is now made by Michelin (has been since about 2001) and a tyre that runs a max of 50 will go well above 60. This is tested and proved. Have a look at some of the Asian vehicles that run BFG/Michelin. They carry 4t on a 2t truck. As for heat, more is generated at lower pressures than high this causing delamination and separations. This is why race cars (V8 Supercars (Holden of course)) start with lower pressures than required. As they heat up the gain pressure.

Unfortunately this is only a guide. It all comes down to the terrain and driving style/load etc. It will come down to what you find as the correct pressure for you.

Remember over pressure wears the middle of the tyre and under pressure wears the shoulder. All manufacturers are different. Nobody drives the same. Once tyres are worn they will continue to wear that way until they are dead (unless you have a wheel alignment issue).

Worthos6 I recommend you start off at 45 and work from there.

thanks guys great info

I used run my D693's at 38.
Just experiment different pressures and apply the 4 or 6 psi rule.

Inflation and the 4 psi rule

Tyre pressures vary for every vehicle and caravan depending on weight loads, size etc. An easy do-it-yourself method for checking you have the correct tyre pressure for your vehicle and caravan is known as the "4 psi rule".

Firstly you need to inflate all tyres to the pressure recommended by the manufacturer, for a "cold tyre" reading and then tow your caravan for say a distance of 100 klm on bitumen.

Upon stopping, immediately recheck your tyre pressure while the tyre is still warm.

If your tyre pressure reading is greater than 4 psi from the "cold tyre" reading you took at the beginning of your trip, then the tyres are getting too hot and your starting tyre pressure was too low. Under inflated tyres wear unevenly and lead to increased fuel consumption. They can also impair the handling of the vehicle in the areas of braking and handling.

If the tyre pressure reading is less than 4 psi from the "cold tyre" reading you took at the beginning of your trip, then your starting tyre pressure was too high. You will need to run the test again (once the tyre has completely cooled) with less pressure until you find the right balance.

It is acceptable for larger 4WD's to have a 6 psi difference between the pressure at the commencement of the trip, and after 100 klm of travel.

Remember to use the same accurate gauge for all pressure readings and always carry a gauge with you when possible.

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Originally Posted by NissPat

I used run my D693's at 38.
Just experiment different pressures and apply the 4 or 6 psi rule.

Inflation and the 4 psi rule

Tyre pressures vary for every vehicle and caravan depending on weight loads, size etc. An easy do-it-yourself method for checking you have the correct tyre pressure for your vehicle and caravan is known as the "4 psi rule".

Firstly you need to inflate all tyres to the pressure recommended by the manufacturer, for a "cold tyre" reading and then tow your caravan for say a distance of 100 klm on bitumen.

Upon stopping, immediately recheck your tyre pressure while the tyre is still warm.

If your tyre pressure reading is greater than 4 psi from the "cold tyre" reading you took at the beginning of your trip, then the tyres are getting too hot and your starting tyre pressure was too low. Under inflated tyres wear unevenly and lead to increased fuel consumption. They can also impair the handling of the vehicle in the areas of braking and handling.

If the tyre pressure reading is less than 4 psi from the "cold tyre" reading you took at the beginning of your trip, then your starting tyre pressure was too high. You will need to run the test again (once the tyre has completely cooled) with less pressure until you find the right balance.

It is acceptable for larger 4WD's to have a 6 psi difference between the pressure at the commencement of the trip, and after 100 klm of travel.

Remember to use the same accurate gauge for all pressure readings and always carry a gauge with you when possible.

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Don't want to be a contradicting bastard but that rule was fine 20 years ago. Same as the tyre placard on cars. Tyre placards recommend pressures for comfort. These days tyres need an extra 10lb (approx) due to the construction of the tyre. Every tyre I have seen since the late 90's requires to be run at 40 to 44 lb (4x4 and passenger) apart from MT's and similar which have a max of about 35lb. I would advise any owner to run a wagon at mid 40's, swb and utes at low 40's.

What ppl need to remember, tyres were constructed of rubber and canvas then rubber, canvas and steel. Now there are very few tyres with canvas (now usually only in the side wall) . To push the tread out enough in modern tyres we need to run a higher pressure due to the amount of steel belts (usually 3 or 4 belts).

Sorry Kris spent to many years in the tyre game.

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Originally Posted by Dhuck

Don't want to be a contradicting bastard but that rule was fine 20 years ago. Same as the tyre placard on cars. Tyre placards recommend pressures for comfort. These days tyres need an extra 10lb (approx) due to the construction of the tyre. Every tyre I have seen since the late 90's requires to be run at 40 to 44 lb (4x4 and passenger) apart from MT's and similar which have a max of about 35lb. I would advise any owner to run a wagon at mid 40's, swb and utes at low 40's.

What ppl need to remember, tyres were constructed of rubber and canvas then rubber, canvas and steel. Now there are very few tyres with canvas (now usually only in the side wall) . To push the tread out enough in modern tyres we need to run a higher pressure due to the amount of steel belts (usually 3 or 4 belts).

Sorry Kris spent to many years in the tyre game.

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All good mate, just what the tyre place tells me to use.

Also, just noticed the bridgestone link Doggy posted above sais not to inflate tyres above 40psi if travelling at high speed

Unfortunately they want us to spend money on tyres. All they see is $$$$$$$$$ for every tyre we buy.

Actually Chris, Defence driving course always contradict Manufacturers and tyre dealers and say add more if travelling long distance to avoid tyre damage. It's all very confusing, I do trust what Dhuck says as it has been taught to me like he says, I've had no probs, and have seen lots of people who disagree with me, have more trouble with tyres than I do.

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Originally Posted by Finly Owner

Actually Chris, Defence driving course always contradict Manufacturers and tyre dealers and say add more if travelling long distance to avoid tyre damage. It's all very confusing, I do trust what Dhuck says as it has been taught to me like he says, I've had no probs, and have seen lots of people who disagree with me, have more trouble with tyres than I do.

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Yeah, definitely not doubting the knowledge and it wouldn't surprise me one bit that tyre manufactures trying to make more $$$ (as usual, and if tyres don't cost enough already).
Its good to have blokes on here with the knowledge to put things straight.

I even did a quick google and even NRMA is trying to promote the 4psi rule....go figure

Anyways boys, very good information:cheers:

G'day mate - welcome aboard. (sorry for the copy and paste introduction, but been away for over a week and a lot of catching up to do!!! LOL). As you've no doubt noticed, heaps of useful information, great people and a good laugh to be had on the forum so make the most of it and get amongst the conversations. Don't forget to throw a few happy snaps of the rig up in the members ride section - we never get bored of looking at them!!!

I have always run my tyres (irrespective of brand) at between 36-38 psi for highway driving - you can increase them to above that for fuel economy reasons etc, but the I find the ride becomes too rigid. In that range, I tend to get the best wear - not too much belly to wear out the centres on highway, not too soft so that the corners scrub out ... all the best with sorting it.

Welcome on board & I hope you enjoy the forum.