Brakes Howl - HELP!

[randy]

Guys,

What causes the front brakes to howl when applied? I'm at my wits end.

I've tried:

-The anti-squeal goop, applied to the pad backs, dried then re-assembled. No relief.

-Rechecked torque on all fasteners - no relief.

- reset clearance on both sides - -no relief.

- removed anti-squeal goop and applied grease instead - no relief.

Here's a clue for you. When I heat 'em up, like apply them hard a few times, the squeal goes away.

But every morning, when it's MOST annoying they howl like a banshee.

I'm pullin' my hair out and I'm running out of hair!

[ratbyk]

Brake Squeal

Randy, couple of tips, suggestions.
1. Chamfer the edge of the pads in a grinder. The leading edge to where the rotor enters as it turns.. Reduces the possibility of the rotor picking up the sharp edge of the pad and starting the chatter.
2. Ensure that you have the anti squeal shims installed between the back of the pad and on the piston and the inside rear edge.

The anti squeal usually works well? Don't understand why it did not or at least changed the frequency of the squeal.
Ken/Sooke

[randy]

Thanks, Ken, but the 79 didn't come with shims, though I could fabricate them. I'm saving that 'project' as a last resort. I'll try the chamfering and let you know.

[Ken Talbot]

I wonder if a PO accidently lost the shims while replacing the brake pads. The '78 fiche shows the shims as part of the caliper assembly, and I know they're there in later models. Also, it would be easy for the shim to be mistaken for part of the pad once it has been on for a while. This might be much like the way the oil filter washer gets lost so often.

[randy]

That's funny (not) my 79 fiche doesn't show a shim!

[randy]

And the '78 does, I just checked with Yamaha.com. So it looks like the howl was in the design!?

[randy]

The 78 fiche only shows an outboard shim. So, Ken, Am I supposed to have one outboard shim on each caliper, or a shim on each pad?

[ratbyk]

Brake Squeal

If you can obtain them, I would place a shim behind all 4 pads. Can't hurt and the one between the piston and the pad is one more barrier to reduce heat transfer back through the piston/brake fluid.
Ken/Sooke

[randy]

That's what I was thinking, too. The only one I can get is the left, but if they're flat I don't see why they wouldn't fit either side??

[ratbyk]

Brake Squeal

Another possibility is to obtain another set of pads made from a softer material. The softer material will be less prone to starting the vibration in the first place. They also provide more initial "bite" as you apply the brakes. Also they are a lot softer on the rotors. The pad wears away faster but rotors will last longer.
The shims if I remember right have a directional arrow stamped in them which could cause problems if not installed as was intended.
Ken/Sooke

[jetmechmarty]

I've known of folks making shims from an aluminum can. It should do the trick.

[Ken Talbot]

Actually, the shims are not flat. I'm trying to find one in my spares and will post a photo. They're designed so there's more meat behind one end of the brake pad than the other. This brings the trailing edge of the pad into contact first, and I believe that's how they lessen the squealing problem. Does that sound about right to you, Ken?

[ratbyk]

Tapered Shims?

A taper in the shim would make sense. I do not know for sure and do not have one to "mike'. That may be why the chamfering of the lead edge of the pad also helps reduce squeal because the rotor picks up the pad a bit further along it's surface to prevent/reduce that chatter/vibration that causes the squeal.
Ken/Sooke

[randy]

Thanks for all the tips, Guys. I whipped up some shims this morning and Oh, Joy, no more howl!

[ratbyk]

Brake Squeal

GOOD! we now know the answer to a solution to the problem.
Ken/Sooke