Squeeling Brakes

[Seangie]

For those who follow along with us...

We recently had our rear wheel bearing seals changed out when up in Montana over the summer.  One of the 2 seals was leaking and the brakes were covered in oil.  We made the decision to change out the brake pads and all the parts and pieces that go along with that.
We only changed the pads on that one leaky side though as the brakes on the other side were slightly worn and looked to be in good shape and not covered in oil.
The issue we are having now is that when we get down to under 15 MPH and apply the brakes at full to bring the bus to a stop the wheel with the new brake pads squeals very loudly.  Its pretty loud and squeal might not even be the correct term to describe the noise. 

I'm assuming that because  new brake pad is slightly thicker than the old pad on the other side that when I apply the brakes the new side is applying more pressure thus causing the noise.

I'm also assuming that I could loosen the slack adjusters to compensate

Is this the correct train of thought or should I be pulling the wheel apart to check something else?

Thanks guys.

-Sean

Wandering the country in a 1984 Eagle 10S. 
www.herdofturtles.org

[Scott Crosby]

Don't loosen a slack adjuster.  If that was she problem it would be rubbing when not applied.   Size didn't matter on the pad more likely it's the material that the friction surface is made of or something is in there like a mount screw came out.  I would take it off to inspect if it was mine.

[oltrunt]

If the drum wasn't resurfaced when the new shoes were installed you may simply have glazed linings from uneven heating of the new lining.  The noise this will produce ranges from a squeal to a ratcheting sound of quite some volume.  Like Scott said, if it was mine i'd take it apart for a look see.  Sometimes you can solve the problem by sanding the glazed areas with 80 grit sandpaper while other times you will have to turn the drum as well.  Good luck!

[Seangie]

We didn't resurface the drum.  In hindsight we probably should have.  Never thought about it till now

Wandering the country in a 1984 Eagle 10S. 
www.herdofturtles.org

[brmax]

No not on this, the application pressure should be the same and a 1/2-3/4" on the slack adjuster rod arm movement under the application is the norm and should be the same side to side.
I understand the noise ( you wonder WHAT THE H IS THAT) kinda like a train locking them up.  The material make up in the pad is the main issue, In my opinion.  The task of getting the drum cleaned is a job (that's what apprentice do, btdt) or myself when there is no one else.  A long time ago I had a shop that would turn a drum cheap, but its been 15 years and the cost is now cheaper to replace the drum if they were wore bad under 150. some under 100. This is on standard dumps and haul, when I first started replacing the replacement cost was like 75.
I have read very little on this but do recall something about pad make up for busses being way different than haul or dump trucks, seems the pad always has its certs printed on the edge where you can see them if inspecting thickness but reading after awhile would be tough.
Im sure some of the bus pros on here have replaced a many rubbin blocks and can chime in much better.
good day there

[HB of CJ]

Did you replace or tank the oil soaked drums?  If not, did you turn your used drums?  Were the shoes arced or matched to the drums?  Once covered in oil, it is difficult to remove any residual oil from lots of stuff, including iron brake drums.  The squeaking is caused by vibrations. 

What is causing the vibration is the question.  Could be several reasons.  Some shoes just squeak when cold.  Others only squeak when very hot.  Some not at all.  You are likely very safe, but the noise is a concern. A complete fix might be somewhat expensive.   HB of CJ (old coot)

[Lin]

Semi metallic pads tend to squeal. Is that what you used?

[bevans6]

Adjusting the slack adjusters has essentially nothing at all to do with the power of the brake application, the speed with which the brakes apply or the relative efficiency of the brakes side to side.  All they do is adjust for the wear of the brakes shoes in the drums such that the push rod extension is within the working range of the brake cannister.  When the brakes are applied the first couple of pounds of air pressure shoots the pushrod out and brings all of the slack out of the mechanism and brings the brake shoes into full contact with the drums - additional pressure creates the friction that slows the wheel.  Adjusting the slacks tighter or looser doesn't affect that in the least, until you set them so loose the cannister bottoms out before the brakes apply.

Brian

[akroyaleagle]

It's probably the material the blocks are made of. If they were relined with longer wearing material they will squeal.

There are materials available that are used on city buses that do not squeal. I think it's softer stuff. we'd not wear them out as soon as city buses.

Here's a little info.

http://www.marathonbrake.com/products/transit/

[eagle19952]

Joe and a few others have it...
Mismatched liner material....there are 7-8 different compositions..
Drums are no longer reasonable to turn, if they meet the thickness DOT spec their good, if not their scrap...
Adjusting (loosening one) is a bad idea..
a shoe an 1/8" off the drum is the same no matter the remaining shoe/lining
are they bonded or bolted on ?
rocks and bolts will squeal....
take'r down the pass and ride the brakes...any residual oil will dissipate or it won't....I would.
then, if my brake performance wasn't what it was, or livable...then I'd think about pulling a wheel..

[TomC]

I know with big rig trucks, a new 16.5 x 7 brake drum is only $85.00. The complete lining and spring kit is around $85.00 also. With those kind of prices, I would replace both sides of the axle with new drums and linings. Do not use metallic or semi-metallic linings as they need to be heated up to work-mainly for in city use. Just use the standard gray block or one that works well when cold. Don't skrimp on your brakes-especially the drive axle that do the biggest part of braking. Good Luck, TomC

[Tony LEE]

Have you tried doing a succession of hard stops (on a deserted road) from say 50mph to 25mph. Supposed to deglaze the friction surfaces.

[oltrunt]

  The "i" spelling and the "e" spelling aside, enquiring minds want to know.  What have you decided to do with the squeal and how have you fixed it?

[HB of CJ]

You have drum brakes?  I confuse easily between pads which I think are for disk brakes and shoes which I believe are for drum brakes.  If you have an older Bus Conversion, your brake drums might be kinda rare and thus expensive to find a replacement for.

We have found that once slobbered in gear oil, various iron/steel parts do not do clean up very well and it is almost impossible to remove all the aforementioned oil.  Hot tanking might work.  How used is the drum and can it withstand being turned again?  Dunno.

Brakes are nothing to mess around with, or to try to save money with.   Like already said before me better, it might be safer and somewhat more expensive to install new drums on both ends of the axle.  Your existing drums may or may not have been already turned too many times.

But ... the big question is how rare are those drums?  How expensive will replacements be?  I dunno.  If everything is working properly, one would expect brakes to work every time and not squeak at all, unless they are trying to tell us something important. Hope this helps kinda.  HB of CJ (old coot)

PS;  Would a cracked drum squeal all the time or only some of the time?  Dunno that either.

[luvrbus]

I would not worry to much about it high humidity will make new brake shoes squeal on a Eagle