Rear disc brake problem

[grassman92]

very interesting thoughts

[Ackattack]

Originally Posted by Frizzle Fry

Ok guys, you ready for some outside-the-box-thinking? This is a pieced together conversion. The MC compatibility is not the problem. I know since I have driven the same setup. Though mine did seem to drag a bit, they certainly provided plenty of braking force. Sounds like the system is well-bled and kink-free.

Here's my question: What is the thickness of your rotors and pads? Did you install pads...? (just kidding ) Assuming impala/caprice rotors, right?

New impala rotors; drilled/slotted rotors from summit...don't now the thickness.

New Hawk HPS pads.


I'll start some trouble shooting tonight and let you guys know what I come up with.

[Ackattack]

So last night I did a little playing around and checking.

I pulled off the electrical connector out of the proportioning valve. I tried pushing the hour glass thing forward. It didn't really move, but it's little, so it may have moved a little.

I fired up the engine. I was able to get the tires to stop a little bit better. But still not that great.

I looked at all the lines again, and found one connection that had a very very small leak, tightened that up (nothing different).

I found the bracket that holds the parking break cable to the parking brake pedal (using a 72 setup) and got that all cleaned up and will install that.

One thing I noted is if you look at the brake rotors, the outside portion (diameter wise) shows that the pads are making contact on both sides of the rotor, but the inside is not (there is/was a thin layer of surface rust on the rotors from the frame sitting outside for 6 months at the paint shop).

Oh yeah....don't know if this is related, but my tranny was a little low on fluid, so I added some fluid (~1/2 qt). I didn't know if this would affect the torque converter locking up....just a thought.

[OhOneWS6]

Those are floating calipers. If it sat out in the weather you may need to remove the calipers and lubricate the pins the calipers ride on. This could cause what you are seeing with contact only on one side of the rotor. Seems unlikely since the contact is occurring on the outside and the piston is on the inside, but worth a shot.

Still seems like a lack of fluid (Could be volume or pressure) to me. Did you replace the line from the frame to the center of the rear end? Did you ever say which MC you are using?

That slider in the proportioning valve should move fairly easily. If it is not centered that could be your problem. Did you check it as was mentioned earlier with a meter or light? The way that thing works is the slider moves when there is a problem and shorts the sender to ground thus lighting the idiot light. When it is in the normal position the sender does not touch the slider.

[Frizzle Fry]

Originally Posted by Ackattack

One thing I noted is if you look at the brake rotors, the outside portion shows that the pads are making contact, but the inside is not (there is/was a thin layer of surface rust on the rotors from the frame sitting outside for 6 months at the paint shop).

By outside portion do you mean the outer edges of the rotor radius, both inner and outer sides, or the outboard/wheel sides of the rotors?

[Ackattack]

Originally Posted by Frizzle Fry

By outside portion do you mean the outer edges of the rotor radius, both inner and outer sides, or the outboard/wheel sides of the rotors?

diameter wise. I went back an clarified my last post.

[Ackattack]

I was doing a little reading and came across this picture posted by Hart_Rob



I'm wondering if not having a spacer in there is causeing the caliper to move when I step on the brake, and therefore load unevenly.....and that is why I have uneven pad contact across the rotor (especially on the back side).....hmmmmm

[Ackattack]

Well I finally got them to work.

After seeing the above picture, I pulled off the wheel. And based on the way the pad was rubbing on the rotor this little offset seemed like it might be the problem. While I was under there I also checked that the pins slid freely and they did. So I added a 7/16 washer between the axle bracket and the caliper "hat" bracket.

Started it up and did some testing. It seemed to stop a little better. So then I bled the brakes again (absolutely no air bubbles). So I tried it again, and it stopped better. It seemed the more and more I pushed on the brakes the better they got.

So then I went ahead and un-jacked the rearend, aired up the front end , started it up and pulled it out of the garage. Seemed to stop just fine.

So I think the "problem" may have been the slight mis-alignment that was fixed with the washers, and then the pads not being broken in like what would be ideal (since I can't exactly drive it down the road to really get them broken in.

Thank goodness this "problem" is behind me, cause it slowed me down for quite awhile.

Time to move on!