Quote Originally Posted by Beefer86
What's your coefficient of friction? What is the surface area of the tires that make contact with the road surface? What kind of brakes?
The figures quoted are an average therefore if you took all the data from all makes of cars then you would be able to work out an average.
Now take an F1 car, there are thousands of points of data that you can take from an F1 car like
Downforce which is adjustable
Aerodynamics which is also fully adjustable
Temperature of tyres
Temperature of brakes

BUT when you break it all down all of the above have one thing in common and that's that they all have an average.

a. An intermediate level or degree: near the average in size.
b. The usual or ordinary kind or quality: Although the wines vary, the average is quite good.
3. Sports The ratio of a team's or player's successful performances such as wins, hits, or goals, divided by total opportunities for successful performance, such as games, times at bat, or shots: finished the season with a .500 average; a batting average of .274.

Satisfactory expanation ?

Regardles of your attempt to muddy the waters it is IMPOSSIBLE for a vehicle travelling on regular roads using even the best of statistics to stop from 40 mph within 12 feet.
Basic physics has shown this in tests carried out by people like these RoSPA : Road Safety