Using the 4psi Tyre Inflation Rule

If you look at the average pressure changes with temperature in the examples then as a rule of thumb, adding 1.75 psi for every 10C change in ambient temperature will get you closer to the intention of the 4psi rule.

The rule was originally proposed by a Pirelli tyre engineer as far as I can ascertain. If you do a web search you will find many people using it.

Craig

Couldn't agree more. The 4psi rule is a 'knob rule' for 'Ruling Knobs'.

I pretty much follow Ocoolone's line of thought and action when setting tyre pressures for the usual four types of terrain that one covers, with special one of scenarios being dealt with as they arise.

DD

"If you do a web search you will find many people using it."
I bet if you do a web search you'll find many people who still think an Energy Polarizer works too :-))
I'm yet to see anyone's explaination of the rule that covers all the varied terrain & circumstances we 4 wheel drivers encounter, in particular how often & by how much the pressures are adjusted in real driving. (Not just the theory)
Cheers Craig...................

Im the same ,life's too short to run round sweating on tyre pressures.
Check em once a month and forget.
Modern tyres are much more adaptable to various pressures and a few pounds either way wont hurt.

I often wonder if the tyre pressure brigade are closely related to the constant car polishers and that other mob who buy the best quality oil and change it twice as often as recommended.

Olcoolone

Spot on dude, I do pretty much what you do and have never had a pressure related tyre problem in 45years of driving on all types of surfaces all over Australia.

May I respectfully suggest that you add a 'smartphone' and/or a Ipad/Tablet to your required white dust coat, coloured pens and highlighters whilst studying for your degree in fourwheeldriveology from the University of Hardknocks 50 miles east south west of the blackstump. LOL)

Once out in the Simpson in the vicinity of Poepels Cnr I noticed on the electronic tyre monitor that the tyres on the passenger side of the vehicle were approx 10psi higher than the other side and I was dead sure they were the same when we started off earlier that day.

The 'worry dagger' in the guts started to stir, however the psi didn't rise any further so I just ignored it. On our return to camp later on, the drivers side did exactly the same with the passenger side returning to the orig setting. It took a while, however it finally dawned on me that it was Sun. Never thought it would make such a difference. Just glad I wasn't wearing a white dust coat that day. (LOL)

Yep the 4psi rule is definitely a knob rule for 'ruling knobs'

DD

When we were selling TyreDogs TPMS we had them on a vehicle and we stopped for about 1/2 sightseeing.... jumped back into the Hilux and the TyreDog was going of it's tree saying the temp in the front right was way to much, ended up being we were parked under some trees and the suns narrow beam was hitting the sensor dead on causing a funny reading.

We would also get strange reading out in the desert in the mornings.... same thing sun hitting the sensor.

I am not advocating the use of this rule at all. But if you do a web search on the 4psi rule you will find many people recommending it and even on this forum, as I recall it, you will find people who have company procedures mandating this rule.

My intention was to alert people to the fact that, if you are going to apply it then you need to understand some of the other variables affecting it.

Far to much mucking around, I run a very simple system which has never let me down. It is a rule of thumb and can be adjusted for extreme conditions.
Highway = 40PSI
Dirt=30 (pending conditions)
Sand=20 (start pressure)

Basic, yes practical yes.
Good luck.
Will

Yep same here....and a good kick off the tyre would give a more acurate reading.
BS

Thank you for that.

I must confess I was a little surprised by some of the responses, given that I was trying to make things safer for those who do use the 4 psi rule, and there are a lot of them.

As you have observed there are a number of members who are "often wrong but never in doubt".

I've always used the 40 - 30 - 20 guideline in the past. Even though it may not be exactly correct it has served me well over the past 40 Years. Maybe a few PSI either way doesn't make much difference ?.

I think I'll check out my current tyre requirements and adjust things up or down as required.

Regards