Wondering what’s brake bias and how it can affect you?
Brake bias — also known as brake balance — is like a matchmaker that decides how much love each wheel receives when stopping the car. It determines which set of your car’s wheels lock up first when you brake.
In this article, we’ll explore brake bias in detail and help you understand why it’s important to address it.
This Article Contains
- What Is Brake Bias?
- Why Is It Important to Address Brake Bias?
- How Does Weight Transfer Affect Brake Bias?
- How Can You Maximize Braking Performance?
- 3 Ways to Adjust Brake Bias
Let’s get started.
What Is Brake Bias?
Brake bias is the ratio of braking force sent to your wheels. This ratio is indicated as a percentage, determining the effective braking power that goes to the front wheels.
A front-wheel-drive vehicle (FWD car) usually has up to 80% front-wheel bias. On the other hand, a rear-wheel-drive (RWD) street vehicle has 60-70% front wheel bias. In other words, in a FWD car, 80% of the braking power is sent to the front wheels, while only 20% is sent to the rear. In a rear-wheel-drive drive car, this force is more equitably distributed.
Note: Just because a FWD car has a more skewed ratio doesn’t mean that it’s improperly biased. You need that level of braking force at the front of the vehicle due to the car setup.
Understeer vs. Oversteer: How Does Brake Bias Affect Driving Style?
Understanding which set of wheels locks up first is critical since it helps you determine if your car will oversteer or understeer.
Oversteer often happens to rear-biased cars whose rear wheel locks up first. When a car oversteers, it turns more than the driver intends.
Understeer often applies to front-biased vehicles whose front wheels lock up first. When a car understeers, it turns less than the driver intends.
Now that you know what brake bias is and how it can affect your steering, let’s explore why it’s essential to address it.
Why Is It Important to Address Brake Bias?
It’s clear that brake bias plays a significant role in how your car behaves. However, most factory-produced vehicles may not actually need brake bias adjustments.
So, why would you be concerned about addressing brake bias in the first place?
If you make any major changes to your car, they could affect its brake bias and maximum deacceleration. For example, increasing a car’s ride height or changing your tires and brake kit can shift your car’s brake bias force. This, in turn, will change how your vehicle behaves while braking.
To further understand why it’d be important to address brake bias, let’s look at the benefits of driving a properly biased vehicle and the dangers of driving a heavily biased vehicle.
1. The Benefits of Driving a Properly Biased Vehicle
A vehicle with perfect brake bias helps you maintain control while braking.
Ideally, a properly biased vehicle is one whose front brakes provide more braking force than the rear. This is mainly because modern front-engine cars have their mass concentrated at the front and require more brake torque (braking power) there.
Properly biased vehicles are easier for drivers to handle and can shorten your stopping distance when you hit the brakes.
2. The Dangers of Driving a Heavily Biased Vehicle
If your car is heavily front-biased, it will send too much brake torque to the front wheels. It won’t turn smoothly, and its rear tire will be underutilized. Its front wheels would lock up and cause rapid front tire wear. This could then end up affecting your car’s overall braking efficiency.
Similarly, a heavily rear-biased car could also affect your braking efficiency. Too much rear brake bias would send too much brake torque to the rear wheels and cause them to lock up. This could result in a dangerous spin when you apply the brakes, especially at a corner entry.
If you end up with a car that’s heavily biased on one axle, this could increase brake pad wear on that axle. It could also lead to either front or rear tire wear, depending on the side that receives too much brake torque.
All this could lead to an unstable vehicle that’s unpleasant and dangerous for drivers.
Now that you know the importance of addressing brake bias, let’s explore how weight transfer affects brake bias.
How Does Weight Transfer Affect Brake Bias?
When you hit the brakes, your car’s weight transfers from the rear to the front. This reduces traction at the back and increases it in the front.
If you have more weight on the front axle, it increases the front brake bias and can overwhelm the front brake pads. When more weight is concentrated on the rear axle, this increases rear brake bias and can overwhelm the rear pad.
Let’s explore how shifting the engine and other physical components can change your car’s center of mass and weight distribution.
A. Changing Weight Transfer By Shifting the Engine
Engine placement plays a critical role in your car’s center of mass. In a front-engine car, a lot of mass is concentrated near the front axle. In a rear-engine car, most of the mass is at the back, on the rear axle.
Depending on the setup, more braking power will need to be distributed to the axle with more mass on it.
As a result, if you shift your engine position, it will change your car’s center of mass.
Your car’s weight transfer and brake bias will also change depending on where you place the engine.
B. Changing Weight Transfer By Shifting Other Physical Components
Engine placement isn’t the only component that changes brake bias.
You can change your car’s weight distribution by shifting other physical components too. You could move items like the battery, seats, and other physical items. You could also change the weight distribution by adding more items inside your car.
Let’s now explore the adjustments you can make to maximize your vehicle’s braking performance.
How Can You Maximize Braking Performance?
Brake balance adjustment is a matter of increasing the front or rear brake bias. But first, you need to understand how a specific brake bias adjustment will affect your braking performance.
To know how to tune brake bias, note what happens when you’re trail braking at a corner entry. If you experience sudden spins that seem uncontrollable, this is a sign of rear brake lockup. To handle this, either increase the front bias or decrease the rear bias.
If you hit the brakes and your steering wheel seems difficult to turn, you’re experiencing front brake lockup. This happens when the front wheels receive too much brake torque. To handle this, you’d need to either increase the rear bias or decrease the front bias.
3 Ways to Adjust Brake Bias
Now that you know what kind of adjusting you need, let’s show you how you can go about adjusting things:
1. Let Your Car Automatically Handle the Brake Bias Adjustment
Here’s a breakdown of how it happens:
In a regular car, the EBD brake system automatically adjusts the braking force sent to each axle. When you step on the brake, the brake system multiplies and transfers your force to the master cylinder, either through a balance bar (brake bias adjuster) or directly. This prevents the wheels from locking up.
If the braking system detects any change in rear wheel speed, it automatically reduces the rear pressure on the rear wheels. This is the same technique that a mechanical proportioning valve uses.
This brake system helps provide the perfect amount of brake pressure required in various driving conditions. This improves braking efficiency and can reduce your stopping distance.
For reference, in F1 car (formula one) racing, the drivers use a remote balance bar or brake bias adjuster knob (like AP Racing or Monit brake dial) to adjust the brake bias while driving.
The Monit brake dial has detent clicks every ¼ turn. Its built-in LCD display shows the number of detent clicks the driver has made from their preferred ‘zero’ point.
This knob is usually fixed on a square mount on the dash. It helps F1 car drivers navigate braking zones with ease. The brake bias adjuster also makes it easy for drivers to safely apply braking techniques such as trail braking.
Race cars also sometimes contain an adjustable bias pedal box that tunes the front-to-rear brake bias. Such pedal assembly adjustments improve racers’ lap time and can reduce their braking distance.
2. Ask a Mechanic to Perform Physical Alterations and Replacements
A reliable mechanic will start by examining your car’s weight distribution and your entire braking system. From here, they’ll help you create an optimal brake bias setup.
They can then alter your brake balance by shifting physical components within your car. They can also change components like the brake pad to adjust its coefficient of friction.
Here’s a list of physical adjustments that your mechanic can make to increase front or rear brake bias.
A. Adjustments That Increase Front Bias
To increase front bias, you could use the following parts:
- Larger front brake rotor diameter
- Rear brake rotor sets of smaller diameters
- Front brake pads with high coefficients of friction
- Rear brake pads with low coefficients of friction
- Front caliper piston of larger diameters
- Rear caliper piston of smaller diameters
- Front axles with less weight
- Rear axles with more weight
- Lower center of gravity
- Less sticky tires
B. Adjustments That Increase Rear Bias
To increase rear bias, you could use the following parts:
- Larger rear brake rotor diameter
- Front brake rotor sets of smaller diameters
- Rear brake pads with high coefficients of friction
- Front brake pads with low coefficients of friction
- Rear caliper piston of larger diameters
- Front caliper piston of smaller diameters
- Rear axles with less weight
- Front axles with more weight
- Higher center of gravity
- More sticky tires for maximum deceleration
3. Get Your Brake Bias Proportioning Valve Replaced
If your vehicle uses conventional hydraulic brakes, then it has a mechanical proportioning valve. This bias valve is usually used in the rear brake lines and limits the amount of brake pressure that goes to the rear caliper when you apply the brakes.
When you step on the brake pedal, brake fluid pressure builds up and activates the bias proportioning valve. It’s worth noting that the size of the master cylinder piston has a direct effect on the brake fluid pressure (also called hydraulic pressure).
A smaller master cylinder will create more hydraulic pressure and will require more brake pedal travel. However, a larger master cylinder can create the same pressure, but with less brake pedal travel.
All of this has a direct effect on the kind of brake bias proportioning valve you should use.
If you’re considering adjusting your brake bias setting, contact a mechanic, and they’ll do the job for you.
Brake bias setting plays an important role in your car’s stability and how it behaves under braking. A properly biased vehicle is easier to handle and will have a shorter braking distance.
However, if you’re experiencing oversteer or understeer, you need to contact an expert who can check your brake kit.
But who should you contact when you need to get your brakes checked?
RepairSmith’s expert technicians perform all kinds of repairs and replacements right in your driveway. All repairs come with a 12-month, 12,000-mile warranty, and you can easily book appointments online.
For an accurate estimate of how much your brake repair will cost, just fill out this online form.