Insights for automotive enthusiasts: Brake bias and how it affects braking performance

02 / 07 / 2021

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Brake Bias and Performance

These days, most factory-produced cars don’t require brake adjustments. If a vehicle has been modified—whether by increasing its ride height or by making any changes to the tires—it’s quite possible that its brake balance has shifted.

Given how critically important brake balance is to how a vehicle behaves—specifically how it behaves while braking—getting this right is one of the most important responsibilities for technicians.

If you’re an automotive enthusiast and are beginning your journey into the industry, here’s everything you need to know about brake bias.

Does weight alignment affect brake bias?

A great way to improve the overall braking efficiency of a vehicle is by shifting the engine or other physical components to change the centre of mass and weight distribution.

When brakes are applied, the weight of the car transfers from the rear to the front. This causes the traction to shift as well, leading the front tires to grip more than the rear.

Having more weight on the front axle also increases the brake bias in front, and overwhelms the front brake pads. This works vice versa if you have more weight focused on the rear axle.

Option 1: Shifting the engine

Engine placement is the key factor when determining a vehicle’s weight distribution and centre of mass. For example, if the car’s engine is in the front, the weight of the vehicle will be in the front as well.

By shifting the engine around, you can make adjustments to both the centre of mass and weight distribution. If done correctly, this move can adjust the brake bias. 

Option 2: Shifting other physical components

Though the engine makes up for a significant portion of the physical components you can shift to adjust the vehicle’s weight distribution, you also have the option of moving around the battery and seats, among other things.

How can I maximise brake bias?

Brake balance, as a concept, is quite straightforward—you either need to increase the front or rear bias (or reduce it). What’s important is understanding how a specific adjustment can affect braking performance. 

If a vehicle experiences sudden, uncontrollable spins when trail braking, that’s a sign of the rear brakes locking up. To fix this, you need to either increase brake bias at the front or reduce it in the rear.

If there’s a resistance in the steering wheel, that’s usually a sign of the front brakes locking up—the required adjustment for this is to reduce front bias or increase rear bias. 

If a vehicle has an anti-lock braking (ABS) system, it will be equipped with an electronic brake distribution (EBD) function that will automatically adjust brake bias. The brake system multiplies the pressure applied on the brakes and sends it to the master cylinder either through a balance bar or directly.

The EBD will automatically adjust the force sent to each axle and prevent the brakes from locking up.  

There are many alterations and replacementstechnicians can do for both front and rear bias, and this is done after examining a car’s weight distribution and brake system.

You can, for example, change the brake pad if you need to change the coefficient of friction.  

Replacing the brake bias proportioning valve is another option you can consider. If the vehicle has a hydraulic brake system, it uses a mechanical proportioning valve. Stepping on the brake pedal increases the pressure exerted by the brake fluid until it builds up and activates the proportioning valve.

Before doing so, however, there are many things to consider, including the size of the master cylinder. 

Understanding brake bias is a fundamental part of technician training

If a vehicle is experiencing either oversteer or understeer, technicians are responsible for understanding exactly what adjustments are required and making them. A proportionately biased vehicle is much more stable and easier to steer; getting this wrong adds a dangerous element of unpredictability to the vehicle’s behaviour.

If you want to learn more about brake bias and how it affects the performance of vehicles, online automotive courses are a great start.

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