There are two schools of thought on whether a motorcycle can stop faster than a car. On the one hand, a motorcycle is much, much lighter than a car so wouldn’t it stop faster than a heavy car? Everyone expects a truck or train to stop slower than a car due to their mass, so the same probably applies for a car against a bike? On the other hand, cars have four brakes, four larger tires to grip the road with and weight remains on the rear wheels even in a heavy braking situation, so perhaps they stop quicker?
Interestingly, if you do a Google search you’ll find that a straight forward answer isn’t forthcoming. Many swear black and blue that a bike will beat a car every time, yet there’s also a lot of anecdotal evidence to suggest the opposite. So what is the answer? Well, it depends…
The most common view is that because a bike is lighter, not only can it accelerate faster, it can also decelerate quicker too. But this is actually completely wrong as you’re dealing with different physics in each instance. For acceleration, a bikes power to weight ratio is often far superior to that of a car and that’s the reason it accelerates quicker. But power to weight has no bearing on stopping.
Let’s break (get it?) down the physics. I’m relying heavily on a wonderful post on the motorcycleforum.com.
Firstly, the force on a vehicle when stopping is:
F = ma
Where F is the force on the vehicle, m is its mass and a is the acceleration (negative in this case).
Next, that force is applied to the tires via traction as follows:
F = μW
Where W is the weight of the vehicle, and μ is the coefficient of friction.
The weight of the vehicle is its mass, m, times the gravitational force, g, so:
F = μmg
The maximum stopping force that can be applied is the maximum frictional force that the tires can cope with, so:
ma = μmg
What all this shows is that we can cancel the use of the variable m as it appears on both sides of the equation. In simple terms, it means that mass has no bearing whatsoever on stopping distances. The equation to thus show the maximum possible deceleration is
a = μg
So (negative) acceleration equals the coefficient of friction of the tires, multiplied by the gravitational force.
So, that light bike you have? When it comes to braking, it’s irrelevant. It’s down to the tires. And because a car has four of them instead of two (and they’re wider), it points towards a car being able to stop quicker. So, cars stop faster than tires. Case closed. Well, not quite…
The reason it’s not so straightforward is that an average bike has far higher performance characteristics than an average car. In general, an average sports bike will have higher quality brakes and better tires than an average hatchback or a family saloon. So your Yamaha R6 or Triumph Street Triple will probably out brake Miss Daisy in her Toyota Camry. But as soon as you get a car that’s remotely sporty, say a Golf GTI, the car will begin to stop in shorter distance than a bike. Physics will win and with those four tires, the equation of a = μg will see the car pull up quicker.
As our video shows, an average bike will outperform an average car. In the future though we’ll put the same bike up against a hot hatch or similar to show how the reverse becomes true. Regardless of what bike you ride or what cars are around, remember that you are your own crumple zone. Always leave plenty of room for an emergency stop as what would be a small fender bender in a car can potentially become a serious injury (or worse) if you run up the back of someone.