The master cylinder looks dirty on the outside too, so let’s give it a makeover. The inside of the piston gets rust protection as well.
Apply metal rubber generously and assemble it. ★
Let’s move on to the front.
Seal groove contamination and dirt between the dust seal and oil seal.
Dirt accumulates in the groove, causing corrosion. The seal gets pushed slightly, and the return action is sluggish.
No tension.
When you inspect the seal, you can tell how well it’s working.
You can also feel the difference in seal design philosophy between brake manufacturers.
No pad remaining.
Using the pad right down to the limit means the piston extends a lot.
↓
Less clearance between caliper and piston means the piston gets pulled by the pad and moves, the body wears down, and the piston develops a step.
When you wash the caliper and try to retract the piston, it catches and won’t go back. The body might be a troublemaker, you know?
It’s important to check pad remaining, but it’s also good to see how far the piston is extended.
