How to Diagnose Side to Side Premature Pad Wear on FWD Vehicles

This article will focus on inner and outer brake pads that wear out faster on one side than the other. This problem can be caused from a variety of sources. In fact, the list of causes is actually quite a bit longer than most technicians know. Due to the lack of knowledge it can be easy for a technician to fall in the trap of trying to fix a part that is already functioning properly. In order to help with this, we've created the following list of possible causes.

Possible Causes for FWD Pad Wear

• Sticking caliper piston on side with problem
• Check valve brake hose on side with problem
• Restriction in ABS modulator preventing fluid release on circuit with ear problem
• Opposite side brake hose with restriction
• Air in opposite hydraulic circuit from problem (i.e. left pads wearing, air is in RF/LR circuit)

FWD Pad Wear Solutions

As with virtually any other mechanical problem, an accurate diagnosis is the first step towards fixing and preventing premature pad wear. As a guide, we've prepared the following directions to help those that encounter FWD pad wear. To begin, an accurate diagnosis of the problem involves 2 components. The first is approaching the problem with a complete list of potential causes (listed above). The second is applying a logical approach to the diagnosis (listed below). 

Diagnostic Approach

1.  Check the brake pedal height and judge it against similar vehicles. If the pedal has excessive travel or feels spongy, bleed and flush the entire system paying close attention to the circuit opposite the side where pad wear is occurring.
2. Test drive the vehicle and get the brakes up to operating temperature. Raise the vehicle on a lift and check for wheel drag on all four wheels paying close attention to the side where the pad wear is taking place. *NOTE: If the vehicle cannot be driven due to metal to metal wear, the system will have to be restored to a functioning state before a complete diagnosis can take place.
3. If the vehicle pulls to the side where pad wear is occurring,  the opposite side brake hose may be restricted. If no other causes of the pull can be determined then brake hose replacement should be suggested. *NOTE: Many FWD vehicles will NOT pull with a side to side brake imbalance due to negative scrub radius (See Image Below). If the vehicle does NOT pull, it does not guarantee the opposite side hose is not restricted. If pressure gauges or clamping plate gauges are available, they should be used to determine side to side braking balance. However, if not available, a good practice is to perform all other repairs and instruct the customer to return after driving a similar distance as they did without the problem. Inform them that the opposite brake hose may still be an issue and this step will determine if it is necessary.

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