Stopping distance does depend on the car, but physics has a bigger influence. The kinetic energy in a car is 1/2mv^2. No matter what car you're in, going twice

Stopping distance does depend on the car, but physics has a bigger influence. The kinetic energy in a car is 1/2mv^2. No matter what car you're in, going twice as fast requires dissipating four times the energy in order to stop. So, take a sporty car with twice the braking performance of a basic car, and you can go 1.44x as fast as the basic car while still having the same stopping distance. I have a very light car that I use on the track, with an amazing amount of braking for its weight. Full deceleration happens at 2.5g, that's not pleasant. There are also comfort limits here.