Rear brake almost froze during ride

It's 80 degrees in the Chicago area and I just took the old KZ out for a ride. About two miles from home, I started to hear a high pitched airy sound which I thought was an air leak. Once I got home, I realized that the bike was extremely hard to move. I suspected front brake, but it turned out to be the rear brake. I checked the brake fluid (which was very low) and added the appropriate amount. As it stands, the bike feels like the rear brake is constantly being applied. Any thoughts on what to do here? I was planning on taking my bike to a local KZ specialist for a tune up and once over, but now I can't even get there!

Ah, the joys of owning a 30 plus year old bike!

does the rear brake pedal come all the way free...ie...is the pedal holding the prssure...if not is the rear brake binding.....

i would

1.) ensure that the pedal is not applying constant pressure...even a tad will heat the pads and cause heating of the set up

2.) i would pump and bleed the system a tad and see if fluid is under a lot of pressure...

3.) check and see if the brake levers plunger rod has the nut spun off some as this will let the rod vibrate tighter,check to see if the brake rod can be wiggled a tad and is off and not staying applied

4.) pull the rear wheel and caliper and pull back the brake covers to see if the piston on the caliper has gunk dried/built up ,as this material will keep the piston from going back down into the caliper, ....this is what i bet is happening if the brake is not jammed on the pedal or rod....

all simple things and can be checked in a few minutes imo...

Thanks trianglelaguna. I just checked, and the wheel is spinning much more freely...probably because it's had some time to cool down. I wonder if everything is OK now that brake fluid has been added.

with out pressing the brake ...maybe take a tube and slip it onto the bleeder nipple and just crack the nipple...normally this allows air to get in but i have a feeling that you have pressure somehow..it imo will shoot a bit into the tube...quick close the wrench and see where the pressure is..peddle...rod/plunger...threaded in too much...try wiggling or turning it out a few turns...


note the fluid in the tube is many years old...i just showed this pic to show how a long clear tube can be routed to run a lot of new fluid into the system without a drip can...

These make brake system work easier: www.speedbleeder.com/

It's typical to start off with a brake that doesn't drag and soon find that you can't even push the bike because the pistons won't withdraw. It's also typical to come back to the bike a few hours later and find that you can move it easily.

Older calipers often get some rust/crud between the piston and the internal parts of the caliper. As TL suggested go ahead and pump as much brake fluid through your system as you can, before you go to the effort of rebuilding your back caliper.

It's worked for me.

Bill

sometimes a tiny brass brush or fine emery cloth and a tiny bit of taking stuff apart...can expose the rear brakes driving piston...brake cleaner or a drop or two of brake fluid(careful it strips paint) applied to the toothbrush sized -brass brush, and some patience , and a guy can get the piston clean enough to recede again into it's hole...a couple of cedar shims/plastic milk jug -cut circles/protectors - and a pair of channel lock or big vise grips, and if you can get a bite on the caliper(careful they scratch super easy) outside, and piston face(brake pad side) grip the pliers as you tap the piston side shim in with a finish hammer and the piston will recede....you also need to have the nipple with the bleeder tube cracked to open...it sounds lengthy but really only takes a few minutes...a rebuild as Bill said may be in order but if you can get it working again....in and out..in and out....then you are good to go...i dont believe that letting it cool and adding fluid cured it...i have had this too...

Same thing happened to mine. Change the fluid, take the brake lever off and clean and grease the pivot rod, take off the caliper and clean it. Make sure you take a small wire wheel on a dremmel and clean out the grove that the seal sits in. Put new fluid in and you should be good to go.

Thanks everyone for your advice! Hopefully I'll have a chance to look at it sometime this week.

Sounds lke it needs an overhaul, not just a band-aid... this is your brakes, albiet just the rear, but whats the condition of the front???

Maybe time to do a complete brake system inspection/rebuild.

Grab your manual and pull it all off... :laugh:

Best of luck.

The cure may be a simple brake pushrod gap adjustment to allow proper "cold" clearance.

See image below (from FSM).

The push rod #3 is threaded, whereby it may be adjusted to allow required adequate clearance (gap) between it and the piston while the brake isn't being applied.

After adjustment, tighten the locknut #4 to maintain the correct pushrod gap.

With zero gap, the brake may function seemingly okay a time or two until the fluid heats up and causes the brake to drag. Results in constant friction of pads on disc, with resultant heat, same as if "riding" the brake, until the brake locks up.

When this happens on the road, may release some fluid -- be careful as the disc is very hot -- which should free the brake.
Allow it to cool before completing final adjustment to the push rod gap.

Good Fortune!