Brake Rotors and Pads

[Robyn]

OK Here we go with Rotors and Pads 101.

The 94 Burb came to use from central Cal with 230K on the clock and a jumpy front brake rotor.

The usual jerking and pulsing when you stop that these things have been known for.

Overall it was not terrible so I have put up with it for the last 4 years.
I replace the pads with medium grade or better and usually dont let them get past the squeekers.

Recently I blast off down the boulevard and touch the brakes only to have the bloody thing almost land in the oncoming lane.

I tried warming the brakes up a bit and nothing helped.

Any slippery at all would get the ABS going nuts.

I stopped off at the Auto Zone and bought a set of mid grade pads and a new rotor for the Drivers side. (Yeah I know, ya should do both)

I got out early this morning and ripped the beast apart. I started with the LH side as this was the one locking and pulling.

Off with the tire/wheel and brake caliper.

As soon as I got the pads off I find that the shim behind the outer pad was turned and ripped as well as wadded up.

Hmmmm this was very odd seeing this as the pads are less than a year old.

I have included Pix of these pads.

I checked the brake rotor for runout and there is negligable runout anywhere in the rotor..

I rip the bearing/hub assembly off and swap out the rotor for a fresh one.
I install the new pads and then reinstall the wheel/tire.

Upon removing the RH side I find a similar mess over there with the pads.

I clean things and install the new matching pads here and finish things up.

The rig drives fine and brakes very nice once again.

I was puzzling pver the TORN and wadded up shims on both outer pads.

I may have a cause. During the cold and snow event of a month ago we used the rig a lot and things got very sloppy during that time and the rig would sit in very cold temps at night.

One morning during a 15F start up I went to move the rig and it hesitated for a second as I applied power followed by a very hard BANG and then all was fine.

I am suspect that the brake pads had frozen to the rotors and when I moved the rig the pads shifted and caused the shim to move and tear and then the bang was everything letting loose.

The outside pad is not captured as well as the one that sits on the piston.

I have never seen this happen before but can't help but wonder if others have had it happen.

Possibly the NAPA brand pads are slightly different than factory ones ?????????.

Once the shim had wadded up it caused the pad to cock slightly and probably explains the grabing and pulling to the Left.

The new rotor solved the pulsing issue as I knew it would.

Hope this helps someone else.

OH an old rotor can be used as a nifty helper when installing the lug studs back into the setup.

With the hub unit off the rig and placed flat on a piece of ply wood or suitable area to avoid damaging the bearing flange.

A large punch placed in the middle of the lug studs coaxed with a heafty swat from a 5 pound hammer will soon see the studs out.

Now after cleaning up the mating surfaces and getting the new rotor sitting on the hub the whole assembly can be placed on top of the old one with the flange facing up _!``!_ with the holes aligned the studs can be carefully driven through the new rotor and back into the hub.

This allows the unit to sit flat and square and the setup to be stable while you drive the studs back in.

The 5 pound club and heavy punch work real well. (Don't swat your hand thats holding the punch)

I am suspect that the issue with the pulsing brakes is not so much an out of round issue as it is a variation in the frictional quality of the rotors due in part to poor quality castings that have varying density and hardness in the iron.
Also it could be that the iron hardens unevenly as it get cycled from hot to cold and or splashed with cold water when hot.

Depending on what sort of material they are tossing in the pot at the foundary. Hmmmm

****Just an update as of 2/2/09*****
I took the nasty looking pads back to the NAPA store and they gave me a brand new set with no questions asked. Seems that these had seen failures both in very cold weather and in very hot conditions too.
The new set has a different shim setup as well as a couple other little changes to the design.

Hope this stuff helps some.

Best

Robyn