The Percentage of Braking Done by Front Wheels: An In-Depth Explanation

For nearly 64 years, the observation about the wear and tear of car brakes has been consistent with the statement that the front brakes do most of the stopping and often wear out faster than the rear brakes. This article will delve into the reasons behind this observation and explore more specific scenarios related to braking percentages and tire wear, particularly in motorcycles and performance vehicles.

Front Brakes vs. Rear Brakes

In most vehicles, the front brakes absorb the majority of the stopping force due to several factors. The center of gravity of a typical car is situated above the contact point of the wheels, which leads to a load transfer to the front when the driver applies the brakes.

Load Transfer During Braking

When you brake, the weight distribution of the vehicle shifts forward, putting more pressure on the front tires and brakes. This is a natural consequence of Newton's laws of motion. In simpler terms, as the car comes to a stop, the center of gravity is shifted towards the front, requiring the front brake rotors to handle a greater percentage of the stopping force compared to the rear brakes.

Effect of Driving Style

The intensity of braking also affects the wear on the brakes. Hard braking causes the load transfer to be more pronounced, whereas gentle braking allows the rear brakes to take on a larger share of the braking force. However, it is generally recognized among mechanics and automotive experts that the front brakes do most of the stopping.

Special Cases and Exceptions

While the general rule applies to most vehicles, there are a few exceptions where the rear brakes play a more significant role in the braking process. Some factors that can influence this include the vehicle's design, load distribution, and driving conditions.

Low-Center of Gravity Vehicles

Very low cars with larger rear tires and large rear wings may see a more balanced distribution of braking force. This is because the rear wheels have more surface area to distribute the load, potentially reducing the strain on the front brakes.

Trucks and Heavy Loads

Trucks carrying large loads on double rear wheels may utilize load sensors to increase brake force, redistributing the load and reducing the burden on the front brakes. This can be particularly significant when the load is predominantly on the rear wheels.

Motorcycles

On motorcycles, the front brakes typically handle about 70% of the stopping force. However, at speeds under about 20 mph, the rear brakes should take over to ensure that the motorcycle safely decelerates without locking up the rear wheels, which could lead to fishtailing or a loss of control.

Engine Position and Braking Force Distribution

The position of the engine and transmission in relation to the vehicle's centerline can also affect the distribution of braking force between the front and rear brakes. In a front-engined car, the front brakes typically handle around 70% of the stopping force, but this can decrease as the engine moves further towards the rear of the vehicle.

Performance Vehicles

In high-performance vehicles like the Porsche 911, where the engine is located behind the rear axle, the distribution of the vehicle's mass shifts towards the rear. This can reduce the braking force on the rear brakes to nearly the same level as the front brakes, making them equal in size and functionality.

Conclusion

Understanding the role of front and rear brakes is crucial for both drivers and mechanics. While the front brakes typically handle the majority of the stopping force, this can vary depending on the vehicle's design and the driver's braking technique. By recognizing these factors, drivers can ensure safer and more efficient braking techniques, leading to better overall vehicle performance and longevity.