Further tyre pressures query

Crackles · Veteran Member

Further tyre pressures query

Hey Jim · Guru

Hi Craig,

I have been towing trailers for 40years.

I tow a 2 ton boat on a tandam triler with load sharing suspension at 100km to Exmouth WA from Sydney 5400km over 7days. I run the tires at 50psi, they do not heat up and I have never blowen a tyre in five return trips. All sealed roads.

Under inflated tyres heat up with the side walls flexing constantly, causing temps to rise and side walls failing.

On our now ex camper @ 1.4ton, we allways ran 40psi and the cars 42-44psi at hwy speeds. Same on graded gravel roads at 80km only. I have travelled on some terrible rutted unsealed roads in our travels and never blowen a tyre. The trailer had full independent suspension.

Drive to the conditions as common sence. Less rolling friction = better fuel consumption. The cars tyres sit flat on the road, and I get 80,000km out of a set. Others have their opinions but I will stick with what I know.

We will be picking up our new van shortly @ 2000kg empty, with full tandum independant suspension, and I will run the tyres up around the 40psi or higher as well. Time will tell.

Jim

PS: Try to avoid the road shoulders at all cost as the broken shoulders Will take their toll on the inside tyres.

-- Edited by Hey Jim on Tuesday 13th of October 2015 11:46:18 PM

Peter_n_Margaret · Guru

I NEVER tell other people what tyre pressure to use because it is not possible to have any idea without having all the information first.
You must know what weight is carried on each tyre and have the tyre manufacturer's data for the exact tyre.
If you don't have that information, NO ONE can give you the correct answer.
If you DO have that information, you will not need to ask the question here.

Cheers,
Peter

PeterD · Guru

Check your tyre pressures for a 3 PSI pressure rise. To do this measure your tyre pressures before you set off on the days trip. At your morning tea stop measure them again. If your pressures are correct the hot pressure will be 3 PSI higher. If there is a greater rise then your tyre pressures are too low (opposite for less pressure rise.) Adjust your pressure and repeat the test next day, keep repeating if necessary until you have thing correct. As P&M said, no one can give you an accurate figure, you have to find the sweet spot for yourself.

Woody n Sue · Guru

I agree with hey Jim get your wheel barrow fill it with sand push it for a few meters and then let the tyre down to half pressure see how hard it is to push a trailer is no different.
Tyres with tread patterns that are not as wide as the tyre walls are bad news off road, stones ect will puncture the side wall in no time lowering the pleasure in these is a disaster waiting to happen.
Drive to the conditions is the best advice going oh and your ability better to take a little longer and make it then have a stack on the way
As I constantly tell the young ones "sometimes it is quicker to go slower "

Baz421 · Guru

Peter_n_Margaret wrote:
I NEVER tell other people what tyre pressure to use because it is not possible to have any idea without having all the information first.
You must know what weight is carried on each tyre and have the tyre manufacturer's data for the exact tyre.
If you don't have that information, NO ONE can give you the correct answer.
If you DO have that information, you will not need to ask the question here.

Cheers,
Peter

Best advice posted here.

Aus-Kiwi · Guru

The OP gave his weights ... I figure between 42 - 50 lb...keep checking tyre temps .. If it's hot to bear hand its way too hot or low pressures.. Better off being a few lb higher than lower ...

snapper49 · Senior Member

All good advice above Will ad that my van has the recommended tyre pressures on the builders plate
Might pay to have a look there

Peter_n_Margaret · Guru

snapper49 wrote:
All good advice above Will ad that my van has the recommended tyre pressures on the builders plate
Might pay to have a look there

Do not rely on the plate information.

It assumes a particular weight and tyre when the van was built, neither of which may be correct any more.

Cheers,

Peter

PeterD · Guru

Peter_n_Margaret wrote:
snapper49 wrote:
All good advice above Will ad that my van has the recommended tyre pressures on the builders plate
Might pay to have a look there
Do not rely on the plate information.
It assumes a particular weight and tyre when the van was built, neither of which may be correct any more.

Those plated pressures will only be starting values. You then need to do your 3 psi pressure rises when travelling (see my post above.) Your are almost guaranteed that the full load travelling pressures will be higher then the plated ones.

JackoFJR · Senior Member

The 3psi rise in pressure you talk from cold to hot pressure is actually 4psi . The claim is if you start at x-pressure and it rises 4psi , you have the correct pressure . If the pressure rises more than 4psi , the cold pressure was to low , tyre has been flexing to much .
If less than a 4psi rise hot , cold pressure was to high .

The 4psi rule as its called , is in the Cooper Tyres Hand Book , it has also been discussed at length on 4x4 forums .

I have tried it on a couple of long trips , my opinion is its BS .

Radar · Guru

JackoFJR wrote:
The 3psi rise in pressure you talk from cold to hot pressure is actually 4psi . The claim is if you start at x-pressure and it rises 4psi , you have the correct pressure . If the pressure rises more than 4psi , the cold pressure was to low , tyre has been flexing to much .
If less than a 4psi rise hot , cold pressure was to high .

The 4psi rule as its called , is in the Cooper Tyres Hand Book , it has also been discussed at length on 4x4 forums .

I have tried it on a couple of long trips , my opinion is its BS .

Was it bs because you had the tyre pressure right the first time or by some chance you may not have taken the time to do the job right.

There is other ways, ie, measuring the foot print of your tyres, time consuming but with rewards, longer tyre life, better handling, ride comfort and braking safely.

Not only for the caravan but also for the tow vehicle, its a science, a simpe science that goes along with loading your vehicles right, setting them up and enjoying the ride, not be taken for a ride.

Baz421 · Guru

JackoFJR wrote:
The 3psi rise in pressure you talk from cold to hot pressure is actually 4psi . The claim is if you start at x-pressure and it rises 4psi , you have the correct pressure . If the pressure rises more than 4psi , the cold pressure was to low , tyre has been flexing to much .
If less than a 4psi rise hot , cold pressure was to high .

The 4psi rule as its called , is in the Cooper Tyres Hand Book , it has also been discussed at length on 4x4 forums .

I have tried it on a couple of long trips , my opinion is its BS .

Another furphy here as the 3psi rule in 1969 when I qualified as a mechanic/diesel fitter was for passenger cars ONLY, and it was a WELL KNOW accepted method.

FROM PERSONAL EXPERIENCE using tyre dogs to monitor pressure for about 4 years, it is the volume of the tyre that dictates the pressure increase from heat generated source. ie 265X75 X 16" tyres increased 5 psi generally but on 41deg C day Streaky Bay to Pt Lincoln they went up 8 psi all round. By comparison the van tyres went up to 5 psi from the 3-4 psi they normally rose.

So as I often say experience can top the "science" espoused by some.

JackoFJR · Senior Member

I have tried the 4psi rule on 3 trips from down here in West Gippsland to Cape York and to the GRR in WA , and back .

Vehicle a Toyota Hilux on 245x70-16, tyres , wasn't towing anything ,

The further North I went the hotter the days were , the more the tyre pressure increased , up to 8psi , in the end I would of had to start with a cold pressure that was higher than the , Max for BFG's , l was using

l checked pressures at almost every stop , I thought it was a interesting project , so gave it a real good go , checking the pressures several times a day .

I have also noticed a 2psi difference in cold pressure from the side of the vehicle in the sun to the other side .