Motor grader tire pressure rule of thumb?
I have one of two Cat No.12's home The 8T has 6 new tires and they have went through several winters without moving. The tires are still in new shape but a little bulgey they had from 10 to 20 PSI. I looked on each tire but could not find the proper inflation pressure. I put 30PSI in them... The size of the tires are 13x24 G-2 TL I know different surfaces require different pressures, I just need a starting place. I Have an Operator and a Maintenance Manual on order and they were supposed to by here the 12th.... . Ha Ha... What the 12th of Never?
Any help will be appreciated
Thanks

Hey Dan, the #14 motor grader book calls for 45 psi max for 14x24 10 ply tires and 55 psi max for 12 ply tires, I'd say 30-40 psi would safe for now.

Tire inflation chart for the #12 8T says 35psi max for 8 ply and 55 psi max for 12 ply with down rating to 28 to 30 psi on rears depending on equipment mounted. I'd post the page but my O & M manual has some water damage making specific attachment conditions illegible. Tire size is 13 x 24.

Hi Team,
from my No12, 8T--80C Motor Grader OMI is the chart that OM mentions above.
Form No 10492-9, Dated 11-57.
Hope this helps.
Cheers,
Eddie B.

On my 112, which is a bit lighter than the Model 12, I run 35 psi in the front and 30 psi in the tandems. 13 X 24 Tires. Still get a heck of a bounce in road gear after it sits for a couple days.

edb Thanks so much👍

Hi, Folks.
A couple of pretty major contractors with whom I worked back in the 1960s and '70s had adopted a policy of running varied tire pressures in the drive tires to help stop what was sometimes called 'elephant walking', rocking from side to side when grading in higher gears.

What they did was to have a 4 - 5 PSI difference in tire pressures between the front and rear tires but with DIAGONALLY opposite tires equal. That is to say that the front tire on one side would be 4 - 5 PSI higher than the rear tire while the REAR tire on the other side would have the higher pressure.

Don't ask me HOW it worked but it did seem to work, especially with radial ply tires like Michelins. It did not completely eliminate the behavior but it did seem to reduce it.

Just my 0.02.

This old 8T starts and runs great but AT UM has a few battle scares. 😱 ... Up Jumped a 😈 devil, the oil cooler is MIA and has been bypassed, just outside the filter housing it makes a hard U-turn and goes back in.🤔 No hill for a stepper 🙂 that's an easy fix after a few ☕️ cups O' Irish mud ☕️ and a red headed Lass Dance.💃...
The temp tops out at 160°F that is fine for hot climates but is on the bottom end of the spectrum in colder climates ... 160°F is fine as long as the temp don't drop too low. Without looking I'd say there is a thermostat in it because the temp comes up in a reasonable amount of time. The gauge looks newer 😂 than 1954 but I guess it could be off just a little.
the pony starts and runs great but needs some time on it to reseat the rings ... just a little... smokes some on second startup of the day and has seemingly substantial amount of gassy smelling oil discharging from head bleeder valves after pony carb runs dry and shuts down..

On my 112, which is a bit lighter than the Model 12, I run 35 psi in the front and 30 psi in the tandems. 13 X 24 Tires. Still get a heck of a bounce in road gear after it sits for a couple days.
So that's what that thump thump thump is ? LOL

I find it hard to read bird poop