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I remembered some data from road march speeds during WW2 (and the 50's) and found something curious. First, let me tell you about the data:
The historical daytime road march speeds* varied from event to event, but the rules of thumb were
4 kph ~ 30 km/day
marching on foot, horse-drawn carts and artillery (not taking into account resting times)
60 km/day
European-style horse cavalry (10 kph for slow canter and up to 20 kph for fast canter for a brief forced march)
18...20 kph
bicyclist troops
20+ kph / minimum 200 km/day (rarely done 150+ km)
This applies to both tracked and half-track motor vehicles. Crew and passengers were exhausted by vibrations and noise. Both troops and vehicles needed many maintenance stops.
This speed probably also applied to motor-towed artillery, as artillery ordnance had poor suspensions and was thus often speed-limited, such as up to 30 kph except in emergencies. Even today most towed artillery is limited to 60 kph.
40+ kph / minimum 300 km/day
wheeled motor vehicles (likely 50...60 kph on good paved roads)
Wheeled motor vehicles had a substantial road march speed advantage (likely more pronounced compared to tracked vehicles than just 3:2*). Yet there was no substantial use of all-wheeled motorized formations as quick reaction reserves. They weren't even undisputedly dominant among armoured reconnaissance in Europe.
The disadvantage of a-wheeled armoured fighting vehicles goes beyond just inferior soft soil mobility compared to tracked and most half-tracked vehicles. The first tanks became shell-proofed instead of just bulletproofed by 1937, a move that wheeled armoured vehicles never matched. They have a too large armoured area compared to the more compact same-weight tracked designs (same problem as with half-tracks unless you reduce the wheeled front to an unprotected skeletonised structure). Armouring wheeled vehicles up to 60+ mm steel would make their ground pressure unacceptable on soft soil (true to this day, despite much better tires and CTIS).
So the wheeled armoured vehicles were not able to prevail in the gargantuan military experiment of the Second World War, despite attempts and already-understood hard soil/road mobility advantages. Even the ability of 4x4 motor vehicles to tow anti-tank guns and the ability to move even divisional field artillery portée (carried for march, set up like towed guns for firing) or as self-propelled guns on wheeled motor vehicles did not lead to such quick formations.
This begs the question why exactly they became such a fashion in 1999...2003 and later (post-2003 rather 4x4 and 6x6 MRAPs than 8x8 APCs). The Kosovo and Pristina deployment embarrassments and armies panicking about "relevance" cannot be the full explanation. Buying all those vehicles was really expensive, so I doubt the advantage in operating costs over tracked vehicles was a strong real argument, either.
The introduction of central tyre inflation systems, wider tyres and improved self-locking differentials did reduce the disadvantage of wheeled vehicles on soft soils, but their rise in weight more than countered this.)
S O
*: I mostly remembered these, but checked Middeldorf/Handbuch der Taktik just to be safe. The minimum 200 km and minimum 300 km figures stem from it, I think both downplay the wheeled motor vehicle mobility of the time. A ratio of 200:450 seems much more plausible during that period. The cruise speed was double and the need for maintenance breaks was lesser with wheeled vehicles. Both tracked vehicles at 200 km an wheeled vehicles at 400+ km would have required one refuelling break, but refuelling was possible by decentralised use of jerry cans and fuel drums.
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