09-20-2021, 07:12 AM
Cleaning pistons; i use a strong dishwashing / water mix with a brush and cloth to get most of the dust off, then dry and clean with brake cleaner.
You could remove the pistons completely which would be better depending how freely they move / are oxidised after the cleaning.
The pistons have a different diameter to correct uneven pressure on the pads but they should all move evenly when positioned when they adjust to the positioning by pushing them in one at a time
Then have a look at any corrosion between the dust seal and the primary seal, ( take them out ) i started to use a tiny amount of silicon grease to protect the alloy cases from water or brake fluid corrosion and it helps a lot to move / place the pistons back in position.
The new pads need to bed in and will feel a bit softer to start with, that's why i measure their travel before and after the job to see if there is any air left in the system, it increases my confidence level.
And it would be a good idea to check for air in the calipers by cracking the nipples after some days just to make sure.
Also clean the nipples by spritzing some brake cleaner in the opening to prevent rusting by cleaning the remainder of brake fluid out of the opening after bleeding, just make sure no fluid comes in contact with the brake pads.
As for the reduced lever travel, could be pistons are stuck ( dirt in the square o-ring grooves ) and not clearing the pads as before, if that is the case the wheels would possibly drag on the disks, my wheels are completely free and only occasionally make a touching sound, you may have seen my video how the rear pads are supposed to be moving and clear the pads when retracted by the seals.
You could remove the pistons completely which would be better depending how freely they move / are oxidised after the cleaning.
The pistons have a different diameter to correct uneven pressure on the pads but they should all move evenly when positioned when they adjust to the positioning by pushing them in one at a time
Then have a look at any corrosion between the dust seal and the primary seal, ( take them out ) i started to use a tiny amount of silicon grease to protect the alloy cases from water or brake fluid corrosion and it helps a lot to move / place the pistons back in position.
The new pads need to bed in and will feel a bit softer to start with, that's why i measure their travel before and after the job to see if there is any air left in the system, it increases my confidence level.
And it would be a good idea to check for air in the calipers by cracking the nipples after some days just to make sure.
Also clean the nipples by spritzing some brake cleaner in the opening to prevent rusting by cleaning the remainder of brake fluid out of the opening after bleeding, just make sure no fluid comes in contact with the brake pads.
As for the reduced lever travel, could be pistons are stuck ( dirt in the square o-ring grooves ) and not clearing the pads as before, if that is the case the wheels would possibly drag on the disks, my wheels are completely free and only occasionally make a touching sound, you may have seen my video how the rear pads are supposed to be moving and clear the pads when retracted by the seals.