Hybrid and Electric cars use regenerative braking systems as well as standard brakes.
Standard brakes rely on friction to slow the car down, similar to how the brakes on a bicycle work.
Regenerative braking systems, use the energy produced by the engine to charge the battery and slow the car down. Most hybrid & electric cars use the regenerative braking system for light to moderate braking, and only using the standard friction brakes as a backup.
While this extends the battery life for your car, it means the normal friction brakes are not being used as much.
So, the standard brakes sit there exposed to rain, snow and salt slowly rusting and become less and less efficient. They also rust between the pad backing plate and the frictional material causing separation which is dangerous.
The traditional way to check brake pads is to measure the thickness in thirty seconds of an inch, but at 100k miles they can measure nearly as thick as new pads! Careful checking the brake components at least every 15000 miles is important for safe and reliable driving.
