Why are the majority of cars able to drive nearly double the maximum speed limit of most countries?

Question

Why are the majority of cars able to drive nearly double the maximum speed limit of most countries?

In: 8

Answer 1

Top speed of a fully loaded semi truck on level ground is like 80mph. Top speed of the same thing going up a steep hill is like 30mph.

Unless you want the same thing to happen in your car, it needs to be more powerful.

A 4000lb car going up a 10% incline at 60mph requires 63 horsepower at the wheels… probably a 90 horsepower engine.

And then why the engine in a modern car is probably 3x more powerful even than that, is to increase fuel efficiency (slower RPM = slower combustion cycle) and to prolong engine life.

Edit: as a point of comparison, cars had 90HP engines around 1940, when most people drove around 45–50mph on open roads. Once interstate driving became common, overdrive and more powerful engines became the norm.

For example, starting in 1955, even Chevy’s started coming with a 160HP V8 instead of a 120HP straight-6.