Re:Tyre Pressure on Gen4 w BFG K02 - still a bit confused

Glad I am not the only one....

My next big upgrade in the next year will be the Des Sol 50mm kit.

Glad I did the tyres first - 195's on a lift kit will look a bit weird on the road.

1.6 to 1.7 bar (24-26 PSI) perfect.

Where did you say you are in SA.?

lookonimages wrote: 1.6 to 1.7 bar (24-26 PSI) perfect.

Where did you say you are in SA.?

We are in White River, Mpumalanga

There is no precise answer but the fundamental principles you describe are correct. Boyles law tells us the relationship between pressure and volume is inverse. The larger the volume, the lower the pressure required to carry the same load. If you want to be academic about it you could calculate the change in volume of the tyres and use that to adjust the pressure. But why not try different pressures and find out what works for you?
I now have the same tyres on my gen 3, and have had KM2s in the same size for the past 7 years. I find 21psi all around works for me, a good balance between grip and confort. If economy is your thing you might want to use higher pressures. If you want good traction then try lower pressures. There is no one-size-fits-all.

The roof rack and bigger tyres already buggered up my fuel economy :laugh: :laugh:

This pigheaded Dutch selfdeclared tyrepressure-specialist" registered to answer here.

Lambert gave in his first reaction directly the right answer, but there are some bears along the road( if I use the right expression) .

The maximum pressure given on tyre is not the pressure for wich the maximum load is calculated.
For standard load passenger cartyre that so called reference-pressure is 250kPa/36psi with afew exeptions to lower. For XL/reinforced/ extraload referencepressure ( further Pr) is 290kPa/42 psi with lesser exeptions.

Then it is best to first add 10% to the determined load, for reserve.

The calculation of pressure for lower then maxload , I got hold of the official calc from ETRTO end 2007 , and went running with it.

Now I use my own calculation in spreadsheets I made , for travel-trailers and the one for motorhomes can be used for every vehicle with some adaption for speed .
The maxload is also calculated for a reference-speed of 160kmph/99mph, for tyres with speedcode Q and up.

It all has to do with the goal of not overheating any part of rubber when driving the speed constantly, for wich the pressure is calculated, and for that a certain deflection of tyre counts.

If you give all the needed info, I will calculate ut for you.
But here a simple do it yourself calculation that comes close .

A .determine axleload and devide by 2 to get weight on 1 tyre.
B. Add 10% to that for reserve.
C. Substract 45kg/100 lbs from outcome B , this is determine by me be carried at zero pressure.
D. Also substract that 45kg/100lbs from maximum load of tyre.
E. Do the division C/D
F. Multilpy E x Pr and this is your advice pressure.
Is highest pressure for the load , at wich comfort and gripp is still acceptable.

Mind that you calculate for highest reserve, but by all the inacuracies , you can end up with only yust enaugh to not overheat the tyre.

Especially determining the loads in your use, is the most tricky part in it all.

Then AT tyres have large profile blocks, that cover part of sidewall , wich gives more heatproduction a cycle as a onroad-tyre, but mostly has the same loadindex/maximum load, as that onroad tyre.
To ve safe mayby even 10% has to be substracted first from maxload of such a tyre is 4 loadindex steps, before you put it in the calculation.

This is also my introduction on this forum.
Greatings from the Netherlands.
( ja dat is ) Peter ( nickname from an old Dutch namesong, translates as Yeah that is Peter)