Author Topic: Rear Brake Caliper 86 FLHT  (Read 240 times)

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Offline popelli

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Rear Brake Caliper 86 FLHT
« on: December 27, 2017, 10:02:05 PM »
Rear caliper on this bike has been problematic for years

It gets hot and binds on all by itself

Have rebuild caliper / replaced caliper / rebuilt replacement caliper

Have replaced master cylinder

Have replaced brake lines

And still this caliper continues to bind on

In short even though every part of the brake system has been replaced the brake is not performing as it should

Have had a few Harleys over the years and the only ones where the rear brake didn't give grief were iron head sporties   80xls and 77xlcr

Have a spare rear caliper and caliper brake to suit a sporty, and quickly looking at it if this was flipped over to fit on the rhs of the bike this should work as disc diameters are the same

Issues identified are
- bleed nipple in wrong place however the caliper can be bleeed then repositioned in place to get around this
- custom brake hose will need to be made up
- swingarm slot needs to be machined out 1/8"
- axle spacers may need to be made up

However I do have a lather so basic machining is not a problem

Has any body done  this and are there any other issues I need to contend with

And before any body suggests buying aftermarket, I have an extremely limited budget so this is not an option


Offline thumper 823

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Re: Rear Brake Caliper 86 FLHT
« Reply #1 on: December 27, 2017, 11:16:29 PM »
Have you any free play at all between MC and foot pedal?
D Troop 3/5, - C/16 ,162AHC, Mekong delta.
Amateur engineering with bad math.

Offline FSG

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Re: Rear Brake Caliper 86 FLHT
« Reply #2 on: December 27, 2017, 11:21:36 PM »
was thinking the same thing, especially are all the parts at the pedal/pushrod end all there and in the correct position

Offline thumper 823

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Re: Rear Brake Caliper 86 FLHT
« Reply #3 on: December 27, 2017, 11:28:28 PM »
I will have to guess
After free play ,  comes a wore out spring in the MC.
Something HAS to be applying pressure to the fluid.
Its not magic.
It is hydraulic.
Wore out  / seized caliper and old seals that do not pull
 back the piston a little after release comes to mind also.
D Troop 3/5, - C/16 ,162AHC, Mekong delta.
Amateur engineering with bad math.

Online Hossamania

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Re: Rear Brake Caliper 86 FLHT
« Reply #4 on: December 28, 2017, 05:04:28 AM »
You could try putting a bungey cord on the brake pedal to pull it back, eliminating that as part of the issue.
Double check your rear wheel alignment to make sure it is not binding the caliper. Check the swingarm to make sure it is not bent slightly.
Make sure the pads are not binding on the caliper, that the slide pins have a slight lube on them.
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Offline mr. pitts

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Re: Rear Brake Caliper 86 FLHT
« Reply #5 on: December 28, 2017, 06:11:01 AM »
If you've been having this problem for years, then the rotor may well be warped. You could also check that the pads are free to move in the caliper. I put new pads in my Electra & had to file a hair of the steel backing plates so they could move freely. HTH.

Offline popelli

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Re: Rear Brake Caliper 86 FLHT
« Reply #6 on: December 28, 2017, 10:02:06 AM »
yes there is freeplay

several different calipers

new master cylder

new rear disc  now on my third have had this bike 20 odd years and last 15 this caliper (calipers) has been problematic

also know other people who have had issues with these calipers


Offline thumper 823

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Re: Rear Brake Caliper 86 FLHT
« Reply #7 on: December 28, 2017, 10:07:56 AM »
Put two springs in the MC
D Troop 3/5, - C/16 ,162AHC, Mekong delta.
Amateur engineering with bad math.

Offline Thermodyne

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Re: Rear Brake Caliper 86 FLHT
« Reply #8 on: December 28, 2017, 10:38:31 AM »
I had that same issue on a 84 FXR.  Rear brake would drag and then lock up on it's own.  Tried every thing.  Rebuilt the caliper, replaced the hose, rebuilt the master cylinder.  Even replaced the master cylinder with one from J&P.   

In the end, on the advice of an old MoCo tech, I bit the bullet and bought a NOS Harley master cylinder, problem fixed. 

Offline popelli

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Re: Rear Brake Caliper 86 FLHT
« Reply #9 on: December 28, 2017, 12:10:30 PM »
"In the end, on the advice of an old MoCo tech, I bit the bullet and bought a NOS Harley master cylinder, problem fixed.  "

Tried that  no difference

Offline Grayrider

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Re: Rear Brake Caliper 86 FLHT
« Reply #10 on: December 28, 2017, 04:55:55 PM »
Sometimes the hose is weak and will collapse when fluid tries to move back after braking. It cannot get back up and holds the pads hard against the rotor.
Replace that hose.
You also did not mention replacing the rotor which may be warped and high spot hits the pads.
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Re: Rear Brake Caliper 86 FLHT
« Reply #11 on: December 28, 2017, 05:35:05 PM »
Sometimes the hose is weak and will collapse when fluid tries to move back after braking. It cannot get back up and holds the pads hard against the rotor.
Replace that hose.
You also did not mention replacing the rotor which may be warped and high spot hits the pads.

He did mention replacing the hose, the switch, and being on the third rotor.
No shirt, no shoes, but I still get service.
Why? Girl, look at this body!

Offline bagga

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Re: Rear Brake Caliper 86 FLHT
« Reply #12 on: December 29, 2017, 03:16:29 PM »
i have an 85 so i think it's probably the same caliper. mine was acting as you described so i took it apart and replaced the pistons with new ones. before i replaced the pistons i felt around inside the caliper bore and it was kind of rough in there. i took some 2000  grit sand paper and got it as smooth as i could. worked fine after that.
1985 flhtc
1976 fxe

Offline kd

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Re: Rear Brake Caliper 86 FLHT
« Reply #13 on: December 29, 2017, 03:25:25 PM »
Easy suggestion first. Is there any way there still may be some air in the caliper that is causing a little pressure increase on expansion. The second suggestion is kinda holding hands with the first one. If the M/C is not returning far enough or is not allowing the residual pressure off when you release the brake the same sort of "barely held on" situation can occur. Is there free play in the actuator rod from the pedal to the master cylinder? Is the piston returning full on release?  It sounds like the full charge is not be bleeding back to the reservoir after releasing the pedal keeping the pad to close to the rotor. On the up side, your rotor would have to be very true for this to occur.

Or, it may just be the piston hanging up.  :wink:
KD