The 14.00 standard tube tire with MIL-profile were replaced with 16.00 tubeless type Michelin XZL. The larger wheel size results in a higher speed (about 8%), the bigger surface helps in mud and sand. Snow chains cannot be mounted anymore, since the distance between the tires on the two rear axles is too low, and on the front axle the distance between the tire and the cab is also too low.
The standard wheels were replaced with aluminum rims from the light tank "Fuchs". These wheels are much lighter than steel rims, and allow an easy disassembly of the tire. Putting the tire back on is also very easy, but getting air in the tire is slightly tricky. With practice and the help of a motorcycle tube it can be done on the road.
The standard valves were replaced with larger and more stable EM-valves, which enable a faster filling and deflation.
Tire pressure monitoring
To check the air pressure while driving, we use TireMoni http://www.tiremoni.com/. A small battery-powered sensor is screwed onto each valve. This sensor monitors air pressure and temperature when the truck is moving, and sends the information via radio signal to a small monitor in the cab. Alarm thresholds for air pressure (min / max) and temperature (Max) can be set. Once a value is outside the set ranges, the system sounds an alarm.
This constant monitoring saved me from having two flat tires on our first tour. I probably would not have noticed the problem without this system (the valves were mounted incorrectly and also of poor quality, we had to take all tires off again and change the valves).
As the EM-valves have a larger diameter, the sensors do not fit, but adapter caps that reduce the EM diameter to standard car valve size are available. These adapter caps are needed anyway, otherwise you could not fill the tires with standard tools at filling stations.