11.00x20: Tire Pressure?

[Bruce Parker (RIP)]

What are the correct tire pressures for British Dunlop s-pattern 'Trac Grip' 11.00x20" run flat tires? The manual for Canadian RF tires (Fox) says 30 front/40 rear (cross country) and 40 front/60 rear (hard road). Would the Dunlops be similar?

[Phil Waterman]

Hi Bruce

Your question is a very good one, in specific to your vehicle but in general to MV load carrying, ride, tire wear, fuel economy, and traction.

I assume you are running the tires on a Fox. The reason I ask is that correct tire inflation pressure, obviously depends a great deal on the weight and speed of the vehicle. Example both my C60L and C60S run 11:00x20 tires the C60S with the Radio Box needs 70-75 psi while C60L cargo I run at 55-60 psi, more pressure than that and the truck rides like it has steel not rubber tires. The other thing that I regularly check along with the pressure is with an IR Thermometer is the actual tire temperature neither truck has ever gone much over 20F over ambient temperature.

The other important load factor check is tire deflection how much fatter is the tire measured sidewall to sidewall at the bottom and at the top. Does anyone in our group have information on sidewall deflection for standard Military Tires and for Run Flats?

Cheers Phil

[Neil Ashley]

From memory I put that pressure or similar in my Humber MkIV tyres.

Any deflection on a run flat with insert is going to be minimal.