Rear breaks keep locking up.....

[joetaco87]

Well the title says it.  After about an hour or so of riding i notice i get less and less play with the rear break pedal and eventually they lock up completely.  I have to loosen the bleeder screw to relieve the pressure.  My first thought was there was too much break fluid  in the resivoir but I wont know till I ride it again.  Im just looking for anyones input or if anyone else has experienced this kind of problem before.

[Hillclimb#42]

Did you just put new pads on?

[joetaco87]

Yea, they had about 2 or 3 rides before this problem first came about.  I also drowned the bike completely underwater but they worked on the next ride.

[BDI]

Have you tried changing the fluid out.

[joetaco87]

I did when i got back from the last ride. It was new fluid but like i said the bike was completly underwater at one point after i did the breaks.  Im going riding tommorrow so ill let every1 know if it was the fluid or not.

[Motorrad]

Take the caliper appart... its stuck/sticky/rusty.   rebuild it if its salvageable.

[joetaco87]

Well, went for about a 6hour ride saturday and the breaks just started to lock up once. I had brought a 10mm wrench along just incase so I bled them out on the trails and it didn't do it again.  Could there have been to much fluid in them so that it couldn't return to the resivoir?

[Danger4u2]

Take the caliper appart... its stuck/sticky/rusty.   rebuild it if its salvageable.

Sounds like the problem.

[kaw rider]

Sounds like maybe you still have some water in the system and it's expanding.

[BDI]

Sounds like maybe you still have some water in the system and it's expanding.

Thats what I'm thinking. If it was stuck do to rust cracking the bleader open wouldn't do any thing for it. I would take the whole rear brake system apart and inspect everything and clean it all out with brake parts cleaner and compressed air to insure there is no water left. the water will go to the lowest part of the system and bleading the brakes might not get it out. The new fluid may just keep going over the top of the water and never push it out.

[KX500freak]

Well the title says it.  After about an hour or so of riding i notice i get less and less play with the rear break pedal and eventually they lock up completely.  I have to loosen the bleeder screw to relieve the pressure.  My first thought was there was too much break fluid  in the resivoir but I wont know till I ride it again.  Im just looking for anyones input or if anyone else has experienced this kind of problem before.

i had an 91 k2,5

it had exactly your issues,
what i found out on my former ride ,was that the calipermounts were worn ,
also the mounting to the bike was worn,
that way it allowed the caliper to move sideways and back and forth a bit .

when you have that issue ,the pads get contact with the disk even while brake is not applied ,
due to this contact they heat up firmly ,the disc gets glowing hot ,and the oil gets to a boiling point
which cause even more pressure and further lockup

also i had my brakepedal adjusted tooo tight  wich caused even a quicker lock up 


all in all   i got a good caliper and gave the pedal more freeplay ,
never had the issue again

succes

[joetaco87]

kx500 - i have that exact problem where the caliper mount is really worn and has a lot of up and down play.  Not the last ride but the one before there was no way to push it out of the woods so i rode it and i had glowing hot embers flying from the caliper.  I looked at the caliper mount and its like 85$ so I figured I'd just wait till i had extra $$ to replace it.  I havn't yet taken apart the caliper to clean it, I havn't had the time.  Once i do ill let you all know how it goes.

[KX500freak]

glad to hear you can use the info ,i was pretty sure cuss i had that same issue too