Thread: 3 PSI rule, does it apply to dirt roads

I was told the 2psi/4psi rule - i.e. 2psi difference for road vehicles and 4psi difference for 4x4.

Tried it for a while and couldn't ever find the Goldilocks pressure. Seemed to always vary too much depending on the weather and specific road.

So now my laziness is to just use 40psi for road, 30psi for dirt and 20psi for sand, as my starting point and then adjust from there if necessary. I've found with my setup on 285/85R16 on Dynamic 16" x 8" wheels that 20psi off road results in the bead seal failing too frequently and that sand will often still requires lower than 20psi.

when it comes to tyre pressure, everyone is an expert and has a different opinion.

i dont think the 2/3/4 psi rule works. there are too many other ambient factors.



i do use 40psi for road, 30psi for dirt and 20psi as a a guide.

3 PSI is neither here nor there in the world of both privately owned and service station tyre pressure gauges. They can vary among themselves by reading up to a 15 PSI difference for any one individual tyre. For the best accuracy I can manage I eschew the cheapies and have a VDO gauge which is never dropped or abused.

Yeah always wondered......but never tried the theory.

Anybody use the theory??

If I put on a new set of tyres, I'll watch the pressures for a while. I try to do it at around 25* ambient temp. If the pressure climbs more than 4 psi in about 30 minutes, I'll add air in about 5 psi increments until it settles to about 4-5 psi difference. That is what I usually run from then on (with the same load, etc), minus 10-15 for dirt/gravel and sand starting about 20. Of course, tyre construction plays a role as well. Because of variations in road surfaces, corrugations etc they are only baseline figures and need to be adjusted accordingly.

I find the rule works in theory, but can be difficult to put into practice sometimes. Tyres facing the morning sun can rise 3-4 psi in a very short time. I generally run 30/36 f/r.... but I drive a mix of dirt and tar roads daily. Will lower if doin continual dirt or raise for tar only, and raise again for load if needed. I found too higher pressures on dirt caused rocks to drill through the cases and caused less traction. I use 4 psi, gets me close.

For the driving i do i have two pressure`s to go to and i don`t stress about the 3 psi rule or any other pressure difference theory
40psi + ON ROAD
25psi For Dirt and Off Road unless it is for a few hours and high speed on dirt roads then a bit higher
On sand it depends on the time of the year i have found so can vary in pressure`s quite a bit so for me no magic number just start at about 22 psi and lower if needed