hi
just replaced rear disc pads and the rear passenger side pads are a bit lazy coming off of the disc, they take about a second to fully release, is this an mot failure
regards
barry
xantia rear disc pads
Moderator: RichardW
If there's any drag on the brakes the MOT will pick it up and fail the car for
binding brakes. There's a chance the caliper is lazy due to dirt ingress or
even damage to the bore or crown of the piston where it's been levered into
the caliper to allow fatter pads to be fitted (not even something you may
have done yourself but a previous owner/garage).
One additional thing I would never have expected until reading about it on
this forum and actually seeeing it for the first time on an Activa recently
purchased is the corrosion twisting the rear caliper effectively levering it
off the rear trailing arm to the point where an edge of the caliper was
actually catching the brake disc!
One final thing to check is the slot in the caliper within which the pads run
in/out from the piston - if there's corrosion/surface rust etc the pads won't
run freely and bind - this is sometimes compounded by poorly sized pads!
Andrew
binding brakes. There's a chance the caliper is lazy due to dirt ingress or
even damage to the bore or crown of the piston where it's been levered into
the caliper to allow fatter pads to be fitted (not even something you may
have done yourself but a previous owner/garage).
One additional thing I would never have expected until reading about it on
this forum and actually seeeing it for the first time on an Activa recently
purchased is the corrosion twisting the rear caliper effectively levering it
off the rear trailing arm to the point where an edge of the caliper was
actually catching the brake disc!
One final thing to check is the slot in the caliper within which the pads run
in/out from the piston - if there's corrosion/surface rust etc the pads won't
run freely and bind - this is sometimes compounded by poorly sized pads!
Andrew
Had the exact same problem when changing front disc pads. Binding brakes, with the wheel raised it took about four seconds from brakes where released to I was able to turn the wheel be hand.
I assumed the piston was binding because it may be rusty where it until now had been exposed to air and dirt. Dismantled the caliper, it looked fine though, greased all critical spots, renewed the brake hose, to no avail.
Turned out to be the caliper fluid inlet/outlet hole, which is situated on the cylinder wall about 15 mm from the bottom. From this hole and downwards the cylinder has slightly larger bore, allowing fluid to enter and escape the caliper even though the piston is pushed all the way to the bottom. A sharp edge can be felt were the bore of the cylinder increases. The caliper had experienced uneven wear, and over time this edge had been smoothed down on the side of the cylinder where the hole is. Consequently, the piston blocked the hole, allowing fluid at high pressure in, but restricted fluid return.
I don't know if this applies to the rear caliper, but if you dismantle the caliper to clean it for dirt and rust, you should check it.
Kristian
I assumed the piston was binding because it may be rusty where it until now had been exposed to air and dirt. Dismantled the caliper, it looked fine though, greased all critical spots, renewed the brake hose, to no avail.
Turned out to be the caliper fluid inlet/outlet hole, which is situated on the cylinder wall about 15 mm from the bottom. From this hole and downwards the cylinder has slightly larger bore, allowing fluid to enter and escape the caliper even though the piston is pushed all the way to the bottom. A sharp edge can be felt were the bore of the cylinder increases. The caliper had experienced uneven wear, and over time this edge had been smoothed down on the side of the cylinder where the hole is. Consequently, the piston blocked the hole, allowing fluid at high pressure in, but restricted fluid return.
I don't know if this applies to the rear caliper, but if you dismantle the caliper to clean it for dirt and rust, you should check it.
Kristian