Thread: Tyre pressures

Do the tyres feel just warm or are they hot? I know about the 4psi rule but usually rely more on temp when fully loaded or towing.
If they feel hot then I put a bit more pressure in them and recheck after another few kms.

Steve

Just did a quick google and found the Maxxi's Bighorns you are running. They have a maximum inflation of 80psi and a max load rating of 1378kg.

If you run these at placard pressures they'll be roughly 2psi under-inflated. To get closer to the right pressures you'd need to be running the fronts at 32psi, and the rears at 40psi or 48psi fully loaded. The placard inflation figures are based on a specific axle loadings - on the rear axle it's about 1450kg for the standard inflation and 1720kg for maximum pressure. If you have a higher axle loading than 1720kg you need to increase the pressure. For example with a 1800kg loading the rears would need to be inflated to 51psi. The weight on the tow hitch would need to be added to the rear axle loading.

You've got plenty of "head room" to inflate the tyres so try bumping up the rears until you get close to the 4 psi rise. Make sure you check pressures about one hour after you do the cold tyre check. The ambient temperature needs to be roughly the same for each pressure check.

cheers
Paul

I've red a little about the 4 psi rule but I'm not convinced you can use it universally across all tyres and sizes.

I posted is another thread about the differances in single make and model of tyre. The construction varies with sizes and that then affects tyre flex which will then affect heat and air expansion which is what is increasing the pressure.

There are just to many variables. I frequently use a tread depth gauge every 10K km or so to see where thing are up to. If the centre is wearing more than the outer, I'll increase pressure. If the centre is wearing less than the outer, I'll reduce pressure.

I thinks it's very dependant on your driving. If you live in Canberra and drive around 100 or so round abouts every week, you'll wear the outer of the tyres more and that area of the tyre will also be generating more heat and wearing the most.

If you drive from Melbourne to Sydney all the time, you wont be doing many corners and the higher speed will create centrifical force and wear the center of the tyre more.

Where the wear is, is where the heat is.

Happy Days.

Can some one explain the 3-4 psi rule? I can't say I've ever heard it

Originally Posted by disco2_dan

Can some one explain the 3-4 psi rule? I can't say I've ever heard it

Quick Google will find plenty mate.

I think it started from some guy who wrote a Magazine articale.

Basicly you check the pressure in your tyres when cold and drive for 20 minutes and check again. If the pressure is more than 4 psi than when they were cold then the were under inflated. If its less then 4 psi more then they were over inflated. Just change your cold starting pressure to suit. Well thats how I red it anyway.

Happy Days

Can some one explain the 3-4 psi rule? I can't say I've ever heard it..

Hi Paul,

I think you should be more focussing on the cold tyre pressures and tyre contact length, and bulge look when warmed up as your guide. The loaded pressures you're running seem too high esp if you're on dirt.

I found the Pink Roadhouse tyre pressure guide to be spot on for high speed dirt driving fully loaded. I gradually reduced my pressures to 24 front and 26 rear COLD with Maxxis LT 245 75 16. 753's. over a few months around oz. this gave the best ride and handling compromise. Fully loaded but not towing.

Cheers
Simon