On Wed, 6 Jul 2005, ravensval wrote:
> I have a quick question to anyone patient enough. I've got 6,900 on
> my A19 and the rear brake is now squeeking when I use it and it never
> has before. I put the bike up on a stand and spun the rear wheel to
Kawasaki uses sintered metal brake pads. They tend to be a bit noisy. That
said, check the pads and make sure they are not worn out. Kawasaki has
specs on minum pad thickness. You can get a caliper from Sears to measure
thickness and use that to see, or if it seems to be getting thin, just
replace the pads.
> investigate. The brake pads sure seem to be gripping the wheel the
> entire way round... I know it wasn't doing that before. This is
By "gripping", what do you mean? Do you mean they make noise as the disk
hits them? Or that they seem to be actually dragging all the way around?
> probably something really simple to adjust... I just don't know how or
Okay, here's the theory. Brake disk pads have no springs to pull them
back. Instead, they rely on the fact that all brake disks are slightly
warped. The high point on the warp will push the brake pads out a bit. So
they should rub at a high point on either side (will not be same point on
either side) because that's what shoves them out.
Now, there is a complication here. The wheel cylinder is full of brake
fluid. If the brake pads are to retract, that brake fluid has to go
somewhere. The "somewhere" is back to the reservoir. But there is a master
cylinder inbetween the wheel cylinder and the reservoir. This master
cylinder has a little hole in it on one end (the end closest to the
bottom, where the plunger goes in fron the brake pedal) to let fluid flow
to or from the reservoir. When you start pushing down on the brake pedal,
the plunger pushes upward, over this hole, and starts shoving the fluid
in the master cylinder up into the wheel cylinder, where it then pushes
the outside brake pad inwards, which also pulls the inside brake pad
inwards since they are on a sliding carrier. As you continue pushing on
the brake pad, the plunger continues trying to go upwards, exerting more
force upon the brake pads. When you release the brake pedal, the plunger
then drops back, and uncovers that hole, and the normal warpedness of the
rotor pushes any excess fluid out the hole back into the reservoir.
> what to look for. Please don't spare any details if you will, I have
> no mechanical background to fall on. Thanks -Valerie
The question is whether the pads are being allowed to retract. Check that
one first. Remove the rear brake caliper (it is held to the big aluminum
bracket with two hex head screws), and make sure it works properly. I.e.,
that the carrier can move back and forth with ease on its bracket.
Lubricate the bracket with brake lube if that is not true, this will cause
the inner brake pad to be a bit 'sticky'. Examine the pads for thickness.
Try to push the outer brake pad towards the wheel cylinder to push the
wheel cylinder back. Half a wooden clothes pin is good here, it will not
break the brake pads and you can pry from both sides with the two halves.
If you can make more room between the two brake pads, there's no problem
with retraction. Put the brake back on (make sure the pads on on either
side of the disc!), bolt it down, spin the wheel. It should spin fine.
Press the rear brake pedal a few times. There should be some drag. If this
is all okay, then your rear brake pads are just being noisy, it's normal,
and don't worry about it.
If you couldn't seem to pry more space between the two brake pads (note
that it won't be a *lot* of space), first try the "if first don't succeed,
use a bigger hammer" approach. That's a big C-clamp. If that's not doing
it, there's two main possibilities here. The first is that the master
cylinder's plunger isn't retracting all the way, thus not allowing that
hole to be uncovered. Check to make sure there's not a mechanical problem
keeping the plunger from retracting all the way, such as a loose bushing
or junk caught in the brake lever keeping it from returning to its normal
starting position. Try pulling the brake pedal up and see if it comes up,
if so then try lubing the brake pedal shaft (see the repair manual) and
see if the spring is present and pushing on th ebrake pedal. Try pulling
the plunger down manually and see what happens. The second is that the
hole itself is gunked up somehow. That is a harder one, but if there was
gunk in the hole, your big C clamp should have made it come loose.
So using your new theoretical knowledge of how the brake system works, and
the cut-aways that you can find on Kawasaki's site, plus the contents of
your Clymer manual, you should have a good start on figuring out what's
the problem. Let us know what you find!
-E
Thanks for the description! --Valerie