Why do cars move slightly backwards just before coming to rest?

Question

You've probably noticed this before: you're in a car or other wheeled vehicle, the brakes are applied, the car's velocity reaches zero, and then the car actually moves backward a tiny amount before it stops moving. Why does it move backward in that last moment?

Answer 1

A car's suspension is not designed to allow the wheels to shift fore and aft relative to the chassis. This would cause the steering geometry to vary under acceleration and deceleration and make the car difficult to control in a turn. Instead, the wheels are tightly constrained to move only up and down in a path established by the suspension geometry.

You can experience this in a car with worn-out ball joints and strut bushings in the front end. This allows fore-and-aft movement of the front wheel spindles and makes the handling of the car distressingly unpredictable.

When you put the brakes on in a moving car, the chassis wants to keep moving forward while the tires' contact patches with the road develop a force opposing the forward motion. The tires themselves, being made of rubber and hence compliant in shear, then develop a shear displacement which relaxes once the car comes to a complete halt- and the car therefore springs backwards very slightly.

Answer 2

The reason here might be because of the elastic nature of tire and chassis, as they might store some potential energy if you suddenly stop the wheel, because the whole body will still be in motion as it was before, due to inertia of motion which will eventually store some potential energy in those shock absorbers of that vehicle or may be in some cases tires which will result in some backward force and therefore will make that vehicle move backwards very slightly.