Brakes binding after fluid change

[Dynamo_Delboy]

So ive changed the brake fluid on my bike on front and rear.

Used the open, squeeze, close, release mode with a mate.

The problem i now seem to have is that my brakes seem to be binding on.

Not major but can feel resistance when simoky pushing the bike forward but if i need to push it backwards its very hard to do.

What could be causing this?

[fastbob]

Sounds like its time to split the calipers and clean out all the crud behind the seals or better still fit new ones. You will be amazed at the difference this makes.

[Guest]

Are you sure they weren't binding before but you never noticed? It does sound as said above that the pistons are stuck in the calipers, but that would have been the case before the fluid change as well.

[Dynamo_Delboy]

Are you sure they weren't binding before but you never noticed? It does sound as said above that the pistons are stuck in the calipers, but that would have been the case before the fluid change as well.

 

Defo not binding before mate.

i could easily move bike forwards and backwards before the change.

Took it out a wee ride tonight and they seem to have loosened off.

Think ill still take calipers off for a good clean

[TimR]

Have you overfilled the reservoirs ? Too much fluid will not give the system enough room for the fluid to retract away from the pistons

[Dynamo_Delboy]

Have you overfilled the reservoirs ? Too much fluid will not give the system enough room for the fluid to retract away from the pistons

 

Both reservoirs are at the max mate. Think i should maybe take a wee bit out?

[fastbob]

If you were able to re fit the rubber diaphragms in both master cylinders without the fluid overflowing then there should be enough room for the fluid to move back and forth. There should be a tiny air vent to the side of the master cylinder covers to allow this to happen. Bear in mind that very little fluid actually moves, its more like a liquid push rod that multiplies the force exerted by your fingers using hydraulic principles. As I said , in my experience, poorly operating brakes is very often down to debris known as mineralization that accumulates behind the caliper seals making them grip the pistons too tightly. Oddly enough, it is the elasticity of the seals themselves and not the action of the master cylinder that retracts the pistons a minute amount away from the disks.

[Stu]

[Dynamo_Delboy]

Thanks for the replies guys

[Guest]

Have you overfilled the reservoirs ? Too much fluid will not give the system enough room for the fluid to retract away from the pistons

 

Both reservoirs are at the max mate. Think i should maybe take a wee bit out?

 

Just loosen the lid on the reservoir, if the problem doesn't stop that's not the problem.

[Guest]

Oddly enough, it is the elasticity of the seals themselves and not the action of the master cylinder that retracts the pistons a minute amount away from the disks.

 

I never knew that, I didn't think the fluid sucked the pistons away, but I just assumed the pads remained in contact with the disc, just with no pressure on them.

[fastbob]

Oddly enough, it is the elasticity of the seals themselves and not the action of the master cylinder that retracts the pistons a minute amount away from the disks.

 

I never knew that, I didn't think the fluid sucked the pistons away, but I just assumed the pads remained in contact with the disc, just with no pressure on them.

I didn't know either until recently , the matter came to light on an earlier post on this very forum entitled Brake Lever Travel. You are right, the pads do seem to remain in contact with the disks, you can hear them when you push the bike. This picture illustrates it quite well.http://i.imgur.com/c9zHdHJ.png