noise first time brakes are applied in fwd/reverse

[Andrew Sasak]

I replaced my front pads and rotors on my 93 Cutlass Supreme a couple weeks
ago. (I used some stuff on the back of the pads to make them stick to the
calipers and cut down on noise.) Since then, the FIRST time I applied the
brakes in forward (after previously applying brakes in reverse), or vice
versa, there is sort of a clunking noise coming from the passenger side (or
even the center, its certainly to my right though). It also doesn't occur
unless the car is actually moving and a large enough force is applied to the
brakes. In other words if I'm just coasting < 5 mph and apply brakes, I
don't believe it occurs, nor does it happen if I apply slight braking at
high speeds, only if I apply a sufficient force to the brakes. Based on the
above information, I imagine the sound is the pad sliding slightly in the
caliper. Can anybody confirm this, or suggest another reason for the sound,
or anything I should do. I've checked to make sure the caliper mounting
bolts haven't loosened. And have even had the wheel off once quickly (to
retighten caliper mounting bolts) and didn't notice anything obviously
wrong. Thanks for any help you guys can give me.

[Rex B]

On Thu, 21 Aug 2003 15:04:44 -0400, "Andrew Sasak" <sasa...@champs.msu.edu>
wrote:

Sounds like what you get when you have the rotors turned and they skip the last
step - applying a non-direction finish to get rid of the minute grooves. Those
grooves are a fine sprial "thread" that kick the pad against the caliper bracket
when the pads bite into them. A mild application doesn't bit the threads so no
noise.

Rex in Fort Worth

[Mike Romain]

Well, something is loose or worn out.

The pads don't shift in the calipers at all, if they can, they are not
in right.

I would be looking close at other front end parts or shock bushings or
control arm bushings or maybe even just a worn out anti sway bar bushing
if you have an anti sway bar. Even a bad engine or tranny mount can
make a clunk.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's

[Andrew Sasak]

"Mike Romain" <rom...@sympatico.ca> wrote in message
news:3F455038...@sympatico.ca...

> Well, something is loose or worn out.
>
> The pads don't shift in the calipers at all, if they can, they are not
> in right.
>

Could be, I know they can slide in the caliper some before the caliper is
put in the bracket, maybe they weren't in the caliper exactly right. I'll
have to check.

> I would be looking close at other front end parts or shock bushings or
> control arm bushings or maybe even just a worn out anti sway bar bushing
> if you have an anti sway bar. Even a bad engine or tranny mount can
> make a clunk.

I sure hope not... I'm not considering that, since it started immediately
after replacing pads and rotors.

[Mike Romain]

The pads can slide side to side in the caliper, that is how they fit on
and move as they wear, but no way they move end to end.

An end to end movement would be needed for a clunk when hitting the
brakes.

If you have end to end play, you have the wrong pads.

I suspect the new brakes are grabbing hard as they wear in like normally
happens and are 'showing' you worn parts that you didn't know were worn.

I also will say if that is the case, then after a few miles the clunk
will mellow out or go away.

Then the new stress from the grab, could also be 'the straw that broke
the camel's back' on a bushing or other part causing it to up and fail
or in the case of a bushing split.

That is not an unusual thing to happen after a repair on a 10 year old
vehicle. New parts can push old ones over the edge. A sharper
deceleration angle on the vehicle can blow out or crack a dried out
shock bushing, etc....

Mike