How fast were regular and F1 racing cars in the 1930's, and 1950's?

Question

what were the capable speeds of both regular cars in the 30's and 50's and F1 racing cars in the 50's

Answer 1

A good guide to Grand Prix (F1 only existing as a set of rules from 1946) car performance is the Alfa Romeo 158 "Alfetta". It debuted in 1938 with a 290kph/180mph top speed and took the first two F1 World Championships in 1950 and 1951 with a top speed of 314kph/195mph.

To give you an indicator of the level of that performance, the world land speed record at the 1938 debut was 502kph/312mph, and in 1951 it was 633kph/393mph.

Of the road cars of the 1930s, an example is the Mercedes SSK, a car designed for both road and racing use, which had a top speed of 200kph/125mph. The Mercedes-Benz 300SL (race production 1952-53, road production 1955+) had a top speed of 140mph (or more, with private tuning).