y rear brake jam up on wr4?

4 replies to this topic
  • dkwok

Posted March 18, 2006 - 02:45 PM


hi guys,
while riding home after a trail ride,
my son wr4 had the rear brake jam up on him,
i had to release some brake fluid thru the nipple b4 the wheel could turn & we could return home,,
i cleaned&serviced the rear caliper & while on the way to the riding area,
the rear brake jam up on him again,
the rear brake disc is not warp,
wat can be the reasons for the lock up???
thanks, :thumbsup:

  • old man dan

Posted March 18, 2006 - 03:00 PM


He may be riding the brake pedal a little and overheating the brake or you may have the master cyl misadjusted (no free play) causing the same thing. The fluid could also be contaminated with water which is boiling under use and expanding and locking the brake. Check and clean the master cylinder.

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  • odonnks

Posted March 18, 2006 - 04:19 PM


Old man has good suggestions.

Think of it this way..if you had to bleed brake fluid to release the caliper that meant the hyd. pressure of the brake system was up as if the peddal was pushed. Like OM said, if the fluid is boiled from the brake pads dragging OR of the fluid is contaminated with something that boils lower than the proper fluid pressure will build and it'll be just like the pedal is pushed.
I'd drain and flush the system with new fluid too.

  • AUS_WR450

Posted March 18, 2006 - 05:54 PM


Further to the other sound advice from my fellow members, make sure that the brake pedal height is adjusted properly. It should be set so that it is pretty much level with the footpeg. The height is adjusted by the screw at the base of the master cylinder.

If it is set too high, your son could be inadvertantly actuating the rear brake in normal riding conditions.


  • dkwok

Posted March 19, 2006 - 04:43 AM


thanks guys,
tink i will service the rear master pump as well
& adjust the pedal height,
will test it next weekend ride,


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