Rear disc is HOT...!!

[guido4198]

I'm running an '85 FXR. Brake systems are totally bone stock. Single rear disc, dual fronts. After riding in normal traffic my rear disc gets too hot to touch ( for very long...), While my dual front discs are not even warm. What's causing such a difference.

[Trip]

Drag ....caused by rear belt(wheel) out of alighnment probably...or, the piston isnt returning far enough cuz its stuck half way open with crud...

[Ricinflorida]

I would tend to agree the pistons in the brake caliper are not withdrawing causing the pads to remain in contact with the rotor. I would remove the caliper, pump the brake with it removed extending the pistons and give them a good wash down with Non-chlorinated brake cleaner. This should remove the dirt, brake dust ect, and allow the pistons to retract fully into the caliper. Which should cure your brake rub. Once the pistons have been cleaned you will of course have to get the pistons back into the caliper in order to get it back on the rotor. Sometimes it can been done with pad spreaders and removing the cap on your master cylinder. In more difficult cases you may need to crack the brake line open in order to get the pistons back where they belong. If that becomes necessary you will need to bleed the brake.
I have got into a habit anytime I pull a caliper for any reason I give the pistons a shot of brake clean just to help avoid this somewhat common problem.

Ric

[Trip]

If he just cracks the bleeder and uses a big C clamp in the piston...he wont need to re-bleed...Speed-Bleeders work real well for this..if the fluid is gray/cloudy..nows a good time to purge the whole line and master..

[FLTRI]

Is this the first time you noticed the heat?
Do you frequently use the rear brake to stop?
I have noticed much more heat from the rear brakes if used at all than the fronts, maybe because there 2 calipers for the front or not as much air getting to the rear for cooling.
Other than that the rear caliper's piston may simply be sticking it the bore, in which case take it appart and rebuild it with the kit available from HD.

[04glide]

I have had the same problem. I just gave the pistons a good cleaning as they were sticking due to crud. It doesn't take much crud to make them stick.

[Mark222]

A failing Master Cyl will also prohibit the caliper (pads) from fully retracting.  Lost a day on a long trip when it happened n a buddy's FLHTCU.  It was older and they had to get the rebuild kit from another dealer.  A "hanging" brake light will tell you if the MC is not releasing pressure.

Mark

[Memnar]

Don't know if this is related, but a guy at work also had this problem and one day the rear brake "locked up" while he was riding.

After much talk we figured he slightly bent the disc one day with his disc lock. He had forgotten it was there and took off, and I guess it was enough to bend it. It locked up a couple of weeks later but he had noticed it was hot after riding to work during those few weeks.

It was on a 2000 soft tail.

[Trip]

Damn right they,ll lock up.....even worse on the old rear juice brakes....bad JuJu!

[guido4198]

Thanks for the thoughts folks. I'll pull the caliper today and do as much cleaning as possible to see if that frees up the piston. If problem persists, I'll move on to the repair kit...If problem still persists...I'll get into the alignment question....Hope I don't have to go there,  but I'll take whatever suggestions you can offer on the subject..!!

[Trip]

First thing you wanna do after you get her off the ground..take a 3/8s and open the bleed valve...if the wheel frees up...you,re gonna be looking at the Master Cylinder , among the rest..