I got burned again today by stepping on the brake and hearing the dreaded metal-on-metal rotor grinding noise. I never heard any noise from the squealer tab (and I do listen for it). I'm in New England (Connecticut) and CT uses the corrosive salt brine in the winter, so I have had the tabs corrode away in the past before they could do their job. Does it matter which way the tabs go - either before or after the pad in the direction of rotation, or it doesn't matter?

 

Looking at pictures from a service manual. The Squeelers are on the inside (Piston side) Brake hose side.
I don't think it should matter much as the wheel rolls both ways but the piston side remains closer to the rotor on the sliding caliper design IIRC.

 

Pads usually seem to wear more on the leading edge, because of the natural way that things get pushed... that edge will wear down first... I usually put them facing that way.

 

That was exactly my thinking also, which is why I positioned the squealer tab that way. But the inner pad was worn down within a hair of the backing plate and the tab wore down also. Now that I think about it, within the last week, I did hear a noise only when backing up. I never heard a thing going forward.
So I tore it apart last night and found that the squealer tab was making the grinding noise. As soon as I heard it, I stayed off the brakes and downshifted when coming to a stop. Luckily I was able to save the rotor with a little sanding. The outer pad still had 3/16" left. I bought myself some time by putting the thickest used pads I had on for now. I think I might have a dragging caliper. The rotor was worn more on the inside than the outside too. Could air in the brake line cause this? I have speed bleeders installed, so I can bleed the brakes easily - if need be.
And in the future, I will be positioning the squealer tab AFTER the pad.

 

Note that the wear sensor is on the leading edge of the pad, which is to the rear of the vehicle. I usually find that they chirp when lightly on the brakes.

Need to lube the sliders for the calipers. The two metal sleeves on the caliper retaining bolts that slide on the rubber o-rings that are in the caliper. Plus the end of the retaining bolts and o-rings (#1, 2, 3, 4 in diagram). I use dielectric grease for this.

And don't forget to squeeze the two retaining tabs on the outer pads, #5 is pointing to one of them.



RBob.

 

Hearing loss at high frequencies? Happens to all of us sooner or later.

You really should visually inspect the brake pads periodically.

 

 

Thanks for those diagrams. And I agree for all the reasons stated about the leading edge.
It's just weird that I never heard anything in the forward direction - only reverse.
But that happens so quickly that it's easy to dismiss. How much time is spent in reverse compared to forward?

So the dragging caliper question - could air in the brake line cause this?

 

Dragging calipers are usually due to mechanical binding (rust on the pins etc.), or restrictions in the rubber lines from rust inside them. Never heard of air in the system causing that. Can't see how it could but what do I know.

 

I ordered brand new calipers and hoses. Before I install them, I will coat them and the brackets with caliper paint for a little extra protection from the winter salt brine used on the roads.