Overheating tyres

Thanks Andrew

I will pass on the good news - I am sure he will be pleased (as am I as he will not be spending more on my inhertiance on load levellers!!)

Regards

Tim

Hi Moose

I agree with your 4psi rule. I guess the problem is that the max (cold) pressure of 44 psi causes an increase of more than 4psi. In that case, what do you do? Obviously increasing the cold pressure to above the max limit is not really an option.

THanks

Tim

You would think the van would have rocker roller system springs and not twin slipper. So the weight on both wheels are the same or should be. 65 psi is a lot of pressure, we don't drive around on that when our cars are fully loaded 3500kgs.
My 2 cents worth

Don't have Pirelli but most AT's like my BFG and Cooper and Toyos sets read as follows --

Max load 1350kg at 65 psi cold (typical figures only)

This actually means that if you put less than 65psi in them they won't carry 1350kg

Many people read in backwards thinking that in this case 65 is max pressure when it is in fact the minimum pressure (for that load).

In this case the tyres are almost certainly under inflated

Robin Miller

Interesting point Robin.
I see an obvious problem here. It's all well and good knowing what the pressure should be in each tyre when there is 1350kg over them but is there a way to know (by knowing this figure - 65psi and 1350kg) what the pressure should be when there is 500kg, 600kg, 700kg, etc over each tyre, as these numbers are more realistic to normal driving.
Alex

Hi Alex

The tyre manufacturers have charts relating to that but basically as you imagine its related to weight within normal use.

E.g. My Patrol weighs 2600 with passengers which is 650 per wheel roughly so my 65psi minimum tyres at 1350kg require
65* 650/1350 or some 31 psi

My 80 psi 235/85/16 tyres then need 38.5 under same conditions.

Of course above adjusted a bit for front/rear weight bias and loads
etc.


Robin Miller

But that Patrol was not running 1350kg per wheel was it?

That is the pressure at which the maximum load can be carried at the rated speeds. it is not the maximum inflation which is typically listed separately.

Yes I know but you can't run a 4x4 at 1350kg per wheel anyhow !!!

Not if you want to be anywhere near legal that is ??

2.4 ton 4x4 , equals 2400kg's, plus overloaded with 800kg's of people and gear,plus 250kg's of towball weight equals 3450kg's plus assuming 2000kg's of that is over the rear axle(which it won't be ) still equates to 1000kg's to each tyre which is still only 3/4 of the max load ???

Now I know some will say they run their 4x4 at more than 3.5 ton, but you probably already know you are running illegal !!!

depends on the 4x4... if you had them on an F-truck, or some other vehicle, then you might be overloading them wihtout exceeding the GVM.

Usually when grey nomads have 4x4s and caravans like that they load the van, and not the vehicle... you'll probably find they would be less than you assessment, but I don't see that mattering anyway.

The 4/6 psi rule should never be called that either - it must surely be a guide, but will be very dependent on what size tyres they are and what pressures are appropriate.

65 psi is not that irrelevant to the situation at all in hot running, in my experience - my Coopers STTs are rated at 1500kg max load at 65 psi COLD.

Anyways, I'm not sure that we are doing anything but violently agreeing, but I know for sure that every situation should be assessed similarly to the way you have done it.

People ought to know what their vehicle weighs unladen and laden if they are doing high stress driving, and this should be a factor in tyre choice.

Cheers
Andrew.

I couldn't agree more, and the more people that "plan" a trip will be more people that spend more time enjoying a quiet drink at the end of the days driving instead of busting their gut changing tyres !!!!!