Front brake troubles...

[Deviant1]

Trying to get Dolores ready for Barber and I've been having ongoing problems with my front brake. I have rebuilt the master cylinder added braided steel lines and replaced the o-ring inside of the caliper. When I got it all back together it functioned perfectly for about 200 miles. Then the brake started squeaking all of the time. Then it started grabbing a little after I released the lever. I hadn't replaced the brake pad on the caliper due cost, so I assumed that the pad was somehow binding. I replaced the pad and again the brake functioned well for a few hundred miles and has started squeaking and grabbing again. What is causing this problem? The piston inside the caliper looked almost perfect. There were two miniscule nicks, but they were so small that I thought the piston would work. I have a spare caliper that I could remove the piston from and see if it is in better shape. Or do I need to just buy a new piston?

 

[Deviant1]

*bump*
Anyone? Anything?

 

[mustang319]

I'm not sure if this applies but is sounds like the caliper itself is dragging or the indicator may have gotten bent.. Are the slides for the pins lubed up so they move? Just like on a car the caliper has to slide on the mounting bolts. If you have slide pins which would look like a bolt clean them up with steal wool and put some high temp grease on them. Compress your piston and mount them up. Do they slide back and forth? Pump up the lever and bleed them out. See what happens.

Did you pick up a stone and thats what you heard. Happened to me.

Is you rotor grooved,warped?

I'm just pitching ideas.

 

[beatnic]

Checking / polishing the sliding pin is a good suggestion. Maybe try checking the rotor for a deep groove or score in it.

 

[teazer]

Sounds like stiff seal in the caliper not working the way it's supposed to. It deforms when the brakes are applied and that deformation helps the piston to retract. May also be corrosion inside the caliper. Try to get a new seal and the strip and rebuild the caliper.

 

[bikeboy]

Or do I need to just buy a new piston?

A couple of things I've found that prevent the caliper from releasing.
1. corrosion in the groove the piston seal rubber sits in. Causes extra pressure on the piston. Did you clean the groove when you replaced the rubber?

2. Blocked master cylinder return hole. This is a *very* small hole that allows some fluid to return and release the pressure on the pads. Not too familiar with your model, but it will be there somewhere. This is my rear master:

hope this helps
ian

 

[Maritime]

A couple of things I've found that prevent the caliper from releasing.
1. corrosion in the groove the piston seal rubber sits in. Causes extra pressure on the piston. Did you clean the groove when you replaced the rubber?

2. Blocked master cylinder return hole. This is a *very* small hole that allows some fluid to return and release the pressure on the pads. Not too familiar with your model, but it will be there somewhere. This is my rear master:

hope this helps
ian

+1 on this one, my GL1000 were dragging all the time and the calipers were great, I had flushed the fluid once until it was clean they worked for a few days then started acting up agian. I re-flushed and as I was doing it a bunch of crud came out of the return hole, I got that out of the master and flushed some more to make sure the return was clean and they have been fine since, find that hole and make sure it is clean. Should be inside the master cyclinder next to the main fluid hole like in the pic above ony in the front brale cup.

Cheers,