A 6000 litre water tank on a two axle 14.5 ton Unimog seems to inevitably involve a fair amount of overloading, unless the chassis has been extensively modified. The maximum tank size on most of these is 4,000, and even the BMPM 6x6 versions can only carry 7,000.
Just confirmed that Unimog has very recently introduced a 16.5 ton GVW upgrade, which explains how this builder managed to accomplish a 6,000 litre water tank on this example! Increasing the autonomy of this type of brush truck by 50% certainly transforms its usefulness, as fire services can handle quite a substantial brush fire with this amount of water.
It will be interesting to see if this spells the demise of the 6X6 Mog, in fire service applications, as this new 4x4 gets within 1000 liters of its capacity, and is potentially less costly.
Added by Rob Johnson on 04 October 2023.