As I know, this particular model with covered wheels was a "Streamline" model of "Type C" racing car, one without the covers and with some changes in overall looks.
Covers were there for aerodynamic purposes, because high-powered versions of this car were used for breaking speed-records on roads, which was very big thing in Germany just before WWII breaked loose.
With Auto Union Type C Streamline, Bernd Rosemayer established world record in 1937., by going 406 km/h (252 mp/h) on the open road. He died in horrific accident year later, while trying to make a new record with 1938. Auto Union's Streamline.
The only competitor for this car was Mercedes-Benz's W125 Streamline, the fastest car on the road ever.
"....Rudolf Caracciola's record of 429 km/h (268.7mph) over the flying kilometre on 28th January 1938, remains the fastest ever officially timed speed on a public road. This record breaking run was made on the Autobahn near Frankfurt, where onlookers were rattled by the brutal boom of the side spewing exhaust stacks as the silver car hurtled past..." (I just love this quote
. Hope that we'll hear those exhaust in the same way in the game...).
The specs for those cars were astonishing:
Auto Union:
about 6000 ccm
more then 600 HP
about 1000 kg
Mercedes-Benz:
5577 ccm
736 HP
1185 kg (curb weight)
Also notice that "normal" racing cars of that time had an average power of 550 HP, and that Rosemayer was one of the rare - if not the only one - able to drive racing version of Type C up to 380 km/h on straights of Nordschleife.
and due to engine sizes being restricted to 4.5L for NA and 3L for supercharged units from 1938 onwards, Grand Prix never saw more powerful cars until the Turbo era came about in the late 70's... Now that's saying something
💡 I guess it must have been a stability thing or something so control was not lost at high speeds
