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New guy with rear brake problems

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mrgreg

New Member
New guy here. I have been working on a rear brake dragging problem on a 2008 FatBoy with 20k on it. The disk is getting very hot even on a very short low speed ride, one mile, without using the rear brake. I recently replaced the rear tire, don't know if that's related??? I was very careful about the rear alignment adjustments.
So far I have,
Removed the calipers and cleaned the pistons and lubed the outside with dry lube. They didn't look that bad.
Cleaned and lubed the two slide mounting bolts.
Flushed the system with new fluid using a vacuum pump.
Checked and lubed the brake peddle at the master cylinder. The peddle is not putting any pressure on the cylinder when at rest.
I took the caliper off and pressed on the brake peddle to extend the pistons against the brake pads and was able to retract the pistons by pressing on the pads by hand.
After all that this evening and taking the short ride I mentioned the disk was too hot to hold on to.
After the ride I was able to wiggle the caliper by hand and the pistons retracted enough so they weren't touching the rotor. Is the caliper too loose? Do I need new mounting hardware?

Not sure what to do next????

I have not checked the run out on the disk yet.

Thanks in advance.
 
I would check you Rotor for warpage. You may want to consider rebuilding the master cyl. also. the piston inside mat not be returning all the way.
tourbox
 
This bike gets used regularly, yes?
Recently changed rear tire then the brake started heating up sure sounds like an alignment problem?
Put it back up on the jack. You need to cover everything from tire alignment, rotor inspection, and the caliper.
 
Follow what tourbox said. Get the rear wheel off the ground so you can rotate it, you should be able to see if the disc is warped when rotated by hand.
Also check the caliper pins for wear, I do not believe you should be able to wiggle the caliper if it is torqued properly. The manual states to torque between 80-120 in-lbs and wear on the pin should be no more than 0.015" when measuring the difference of a worn and unworn part of the pin.
 
436450_400x400.jpg

You can rent 1 of these to check run out
Your master cylinder may be holding pressure on the caliper, pump up the brakes 3 times, release the pedal, crack the bleeder loose did fluid spurt out?
 
Well, I found my problem. The rotor was really warped. After I removed it I didn't need a dial micrometer to check the run out. I could of used a yard stick. The only question I have is what would of caused the warp? Is this a common problem? What can I do to prevent this from happening again?
 
building the master cylinder is a good idea, mine was full of a sludge deposit, not helped by the previous owner using the wrong fluid.
I also replaced the stock brake hose with a Goodridge braided hose, I was advised that the old hoses can break down inside and whilst looking ok on the outside, thus restricting the back flow of fluid, my disc got too hot to touch!
 
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