Bought the bike in early '06 with 30,000 miles. Last summer the rear brake started acting unusual, stopping sometimes, going to the floorboard other times. Dealer diagnosed a warped rotor & installed a new rotor & pads. Stopped fine all of last riding season.

Rear brake was OK at the start of this season, but the pedal gradually goes down over a period of a couple of weeks, until there's no braking at all. Thorough bleeding restores braking, but lasts only about two weeks.

Tech at the dealership said it sounds like either worn master cylinder seals or worn piston seals, and I agree - the leak is so small that there's never a drop underneath the bike. My only concern, other than the seals, is the rear caliper temp. After riding home from work today, 20 miles at 70 to 80 mph, the rear caliper showed a temp of 262f. I understand that the DOT 5 fluid is good to 500f, but thought that 262f is perhaps higher thanit should be. Both front calipers showed 109f. All temps taken with a Fluke 62 infrared thermometer.

 

Sounds like the rear caliper is hanging up and dragging on the rotor. Wonder if they cleaned off the pistons beforepushing them back in to the caliper last year when the new pads were installed. All the dirt that builds up on them can ruin the rubber if not cleaned off first before pushing the piston in to the caliper.

 

Ihad this happen to my 03 deuce when i was in Phoenix. I had to rebuild my rear master cyl with a rebuild kit. The kitsare fairly cheap and very easy to install. One snap ring and the plunger with an o ringand spring in the master cyl can be removed and replaced. Takes less than an hour to remove the master cyl, rebuild and bleed the brakes. When they go bad your brake can go all the way down when you push on it or, and this is what happened to me, the bad cyl will not let enoughfluid back into the master cyl when you release the brake and the fluid in your caliper heats up and expands.The fluidcan'tgo back into the master cyl so itpushes the pads against the rotorheating them up. I rebuilt mine in a motel parking lot and haven't had a problem with it since.

 

I also thought about the possibility of a dragging pad or pads ...

The bike is on the lift table now, a bungee cord applying pressure to the pedal. Maybe a drop of fluid will come out of the caliper or the master cylinder - should know by morning.

Cowboy, we posted at the same time ... surely sounds like what mine is doing.

 

Bought the master cyl rebuild kit, which consists of replacing the master cyl cartridge. An easy job for the home mechanic, as Cowboyglide already said. My install was probably somewhat easier than his, with the bike raised up on the Handy Air Lift, good rock music playing, and a cold beer or two to help the process

Bled the system, raised the rear wheel, checked to see if there was still drag. Less than before, but more than there should have been. Looked closely at the relationship between brake pad & caliper and saw much less space between the inboard pad & caliper than between the outboard pad & caliper.

Pulled the rear axle, removed the right side spacer which measured 0.475" . Figured that the caliper needed to move to the left (toward the wheel) and faced 0.025" off each end of the spacer. That left the spacer at 0.425". Installed the axle, tightened the nut to spec, and looked again at the pad/caliper spacing. Seemed to be look about right.

Rode to work today and checked the the caliper temp ... 141f[&:]

Hard to believe that a new master cyl & a 0.050" caliper relocation dropped the temp over 100... but am happy that it did.

 

After riding with the new master cyl for a couple of days, noticed that the bottom of the caliper was shiny with brake fluid[&:]

Bought the caliper rebuild kit at the dealership, about $65. Four new pistons, eight seals, two O-rings. Read through my service manual a couple of times, looks like this should be home shop doable ... at least my front brakes are strong.

Will post back after that job is done.

 

Hope you get it squared away. Brakes are the last thing you want to worry about riding down the road.

 

Hopefully the last chapter in this story

Put the bike on the lift yesterday morning, removed the right muffler, pulled the rear axle & removed the rear caliper. Followed the instructions in the factory manual & forced out the old pistons. Removed the old seals, cleaned the piston bores with a toothbrush & Simple Green until spotless. Blew everything dry, installed the new seals, installed the new pistons, reassembled the caliper, bled the system& put the bike back together.

Took a five mile test ride on a road that allowed lots of braking. Got the rear brake hot enough that I could smell it ... not a drop of DOT5 anywhere. Went on a 220 mile ride, again not a drop of fluid to be seen or felt.

The rear caliper looked intimidating, but turned out to be an easy home-shop repair (with the factory manual close at hand). With the rebuilt caliper, new master cylinder, and fresh DOT5 fluid, the rear brake finally works as it should. Figured that my dealer would have spent at least 4 hours on what I did, at $68/hour ... well worth the effort.

 

Barry, Glad to hear you got it fixed.

 

This looks exactly the same as I have on my 1992 Heritage softail, exept of leaking oil.

during coming down hills my rear brake heats up, and keeps on more braking along the way, until finaly it fast slows down the whole machine when I cut the throttle. The prake pedal does not have any presure and I can push it to the bottom.
probably the rear caliper is hanging up and dragging on the rotor.

I brought it twice to the mechanic, since I am not very known on those issues.

first he cleaned up the whole brake cirquit, where a lot of particles came out of the tubing.
the second time he changed the brake pump, and now I still got the same problem.

I expect the rear caliper being more than dirty, and maybe the rubbers are ruined.

Since comlpete calipers are more than expensive, I would like to have them revised, I understand there are caliper rebuild kits, would that kit help me to solve the problem?