Why do Subaru rear brakes wear faster?

Subaru vehicles are known for their all-wheel-drive (AWD) capabilities, but this design can also lead to faster wear on the rear brakes compared to the front brakes. The primary reason for this is the way power is distributed in Subaru's AWD system, which places more braking load on the rear wheels.

Power Distribution in Subaru's AWD System

Subaru's AWD system is designed to provide a 60/40 power split between the front and rear wheels, respectively. This means that under normal driving conditions, 60% of the engine's power is sent to the front wheels and 40% to the rear. This uneven power distribution puts more braking load on the rear wheels, which can lead to faster wear on the rear brake pads and rotors.

Braking Forces and Wear

When braking, the weight of the vehicle shifts forward, increasing the load on the front wheels and brakes. In a front-wheel-drive (FWD) vehicle, this weight transfer helps the front brakes do most of the work, leading to more even wear between the front and rear brakes.

However, in a Subaru AWD vehicle, the rear wheels are still receiving a significant amount of power, even during braking. This means the rear brakes have to work harder to slow the vehicle, leading to faster wear on the rear brake components.

Factors that Contribute to Rear Brake Wear

• Uneven power distribution in the AWD system: The 60/40 front/rear power split places more braking load on the rear wheels.


• Weight transfer during braking: The forward weight shift increases the load on the front brakes, while the rear brakes still have to work hard to slow the vehicle.


• Driving conditions: Aggressive driving, towing, or carrying heavy loads can further increase the braking load on the rear wheels.


• Brake pad and rotor quality: Lower-quality brake components may wear out faster, especially on the rear axle.

To help mitigate faster rear brake wear, Subaru recommends regular brake inspections and maintenance, as well as using high-quality replacement parts designed for the AWD system. Drivers should also be mindful of their driving style and avoid excessive braking or heavy loads that can further stress the rear brakes.

What is the 30 30 30 rule for brakes?

The "30-30-30 rule for brakes" is a procedure for breaking in (or bedding in) new brake pads and rotors, involving 30 slow stops from 30 mph, with a 30-second cool-down between each stop. This process ensures the pads and rotors develop an even layer of friction material, which improves performance and prevents issues like vibration and glazing.
 
How to perform the 30-30-30 rule

1. Find a safe, open area with light traffic where you can complete the stops without interruption. 
2. Accelerate smoothly to approximately 30 mph. 
3. Apply the brakes steadily to slow down to about 5–10 mph. Avoid hard or emergency stops, which can cause problems. 
4. Hold in neutral or coast for about 30 seconds to allow the brakes to cool. This prevents the hot rotors from warping. 
5. Repeat this process for a total of 30 cycles. 
6. After completing the 30 cycles, drive normally for about 300–500 miles, avoiding hard or high-speed braking to allow the system to settle. 

Why bedding in is important

• Improves contact surface: It ensures the brake pad material is evenly deposited onto the rotor surface. 
• Maximizes performance: It leads to immediate braking response, consistent pedal feel, and predictable stopping distances. 
• Prevents problems: Proper bedding reduces the risk of brake fade, glazing, noise, and vibration. 

Why do my rear brakes wear out faster?

Rear brakes can wear out faster due to a combination of modern vehicle features like electronic stability and traction control, which use the rear brakes to prevent wheel spin. Other common causes include driving habits, such as frequent stop-and-go traffic, and mechanical issues like sticking calipers or slide pins, which cause the brakes to drag.
 
You can watch this video to learn about the causes of uneven brake pad wear: 59s4DIYersYouTube · Jul 4, 2016
Common reasons

• Electronic Stability and Traction Control: Modern cars use these systems to apply the rear brakes to correct wheel slip or prevent nosediving, which happens thousands of times without the driver's awareness. 
• Stop-and-Go Traffic: This type of driving accumulates wear on the rear brakes because they are frequently engaged to manage wheel spin. 
• Mechanical Issues:
  • Sticking Caliper Pistons: If the caliper piston doesn't retract properly, the brake pad will constantly be in contact with the rotor. 
  • Corroded or Sticking Slide Pins: These pins allow the caliper to move; if they are corroded or dirty, the caliper can't move freely, causing the pad to drag. 
  • Restricted Brake Hose: A collapsed flex hose can restrict fluid flow, keeping the brake engaged. 
• Handbrake Usage: A rear handbrake that is stuck or not fully released will cause constant drag. 

Other potential factors

• Driving Habits: Aggressive driving or carrying heavy loads in the back of the vehicle can shift weight forward, but if you are braking gently or often, the rear brakes are applied more frequently. 
• Road Conditions: More grit and grime can get kicked up towards the rear brakes, and corrosion on the rotors can increase wear. 
• Brake Proportioning Valve: If the proportioning valve is malfunctioning, it can send too much pressure to the rear brakes. 

This video explains how to diagnose and fix sticking brakes: 36s8020 AutomotiveYouTube · Oct 1, 2023
What to do

• Check for Mechanical Problems: During your next brake inspection, check for sticky slide pins, stuck caliper pistons, or any other mechanical issues. 
• Inspect Your Handbrake: Ensure your handbrake is fully disengaging after you release it. 
• Vary Your Driving Habits: Try to be smoother with your braking, especially in stop-and-go traffic. 
• Disable Traction Control: In a pinch, you can turn off traction control to see if it helps reduce rear brake wear. 

How long do rear brakes last on a Subaru Outback?

between 30,000 and 70,000 miles
Subaru brake pads usually last between 30,000 and 70,000 miles depending on your driving habits.

Why do Subaru rear brakes wear faster than front?

The reason as to why the rear breaks wear faster is because they're often smaller. Both the rear pads and rotors are smaller than the front. It's not more complicated than that.