The W163 is much the same as the W154 aside from the new bodywirk and the M 163 V12 engine. Chassis and suspension components are almost unchanged compared to the W125.
Braking was much improved compared to the earlier W125 and W25 designs. The largest drum diameter that fit within the limits of the rim were used. Inside each drum was twin light-alloy shoes which were operated by hydraulic pistons. Cooling to the drum was ample with the inclusion of angled veins which moved the air centrifugally over the out side of the drum.
Of special interest is the position within which the engine was mounted. The V12 sat at a downward angle compared to the chassis. This allowed for the driveshaft to incline downwards, sitting lower near the rear of the car. This meant driver’s seat could be mounted lower which resulted in a lower center of gravity. This drivetrain setup is also observed in the type W154.
In 1938 the AIACR restricted engine size such that the upper limit of engine capacity was limited to 4.5 liters unsupercharged and 3.0 litres supercharged. The result of this regulation caused a slight decrease in power for grand prix cars. In general, 1939 cars had the same power as that of the earlier unrestricted 750kg forumla cars. This meant the new 3-litre formula rules failed to reduce the speeds involved in forumla racing . Furthermore, remarkable improvements in road handling, braking and aerodynamics for the 1938 & 39 seasons kept the cars ahead of their 1937 unrestricted predecessors.