Help, Rear Brake Noise After Pad Change
 

Changed my brake lines to stainless, fluid to DOT4, and pads to Porterfield R4's. Bled the entire system (clutch too). Brakes feel good, a little spongier than OEM initially but very firm as you push more into it, also no squeks at all yet? Didn't expect that. Haven't given them an honest workout however, no bed in process etc... Problem is a noise from the rears every time I touch the brakes going a new direction.

What I mean by this is when I tap my brakes rolling backwards down my driveway I get a bit of a bonk from the rear calipers. Again the first time I touch them after moving forward, but then it's gone until I change direction again. So its like a slop thing, something moving from side to side loosely.

I did not put the backing plates on the new pads. Very thin plates wrapped around the OEM pads. Could this be the issue? The brake pads have a little slop without this shim and slide fore/aft when torqued? Any suggestions or relevant experiences would be helpful

Turned out to be a torque wrench I left in the trunk rolling around. Can't believe I missed this...

Talking to thin air here, but removed everything from the trunk and the noise is indeed coming from the brake pads/calipers.

Well I'm not brake expert but I'd have a reputable shop take a look at your handy work and help troubleshot the problem. Sounds like you forgot a clip or something....

Either pads are walking in the caliper, or caliper is walking in the knuckle. Something there is loose, or pads aren't fitting tightly to the caliper. There should be no slop there. Go fish.

I have the exact same issues with one of my vehicles. The problem with my car is a very old caliper hanger/caliper. Excessive wear allowing it to go up and down. Look for up and down movement in your calipers/brakes. I don't think the lack of shim would cause this.

Thanks guys for the input. I called Porterfield today and they patched me straight through to a knowledgeable mech, they were very helpful, I really like the vibe I get from them. Anyway, he said there was supposed to be a backing plate or shim thing included w the rear pads (I'm positive they weren't included however). Anyways he said to just re-use the ones from the OEM pads which is easy enough to do. He said recently these rear shim things have started wrapping around the pad and add to overall size/dimension of them, meaning if you leave them off you get some slop. He said it wasn't dangerous to drive as is carefully until next weekend when I can get the car back up on the lift. Will update with results likely on Saturday night.

Update:

Got the car up on a lift and pulled the rear pads out. Compared to stock, they are indeed slightly different sizes, similar thickness and similar height but the length is off by about 1/8" or so. This means when the pads contact the rotor they "tilt" slightly before being stopped by the caliper. Placed the OEM rear shims on the Porterfields but that does nothing to change this dimension, so therefore no change. Spoke with Porterfield one last time who said perhaps my specific pads were cut from a different size to fulfill the order or something but other than that had no idea how this happened, the rears should have been a standard part number with no "hand cutting" necessary.

In any event I just decided to go for it as-is for my HPDE weekend. Put the Porterfields back in and bedded them in. Felt great after a few hard stops (barely worked at first as is to be expected) and really have the right front/rear balance that I want. Firm stop from 140mph to about 30mph can be done with your hands off the wheel, no vibration, no pull to one side, works great.

Completed 8 20 minute track sessions this weekend with all 4 Porterfield R-4 pads in place. I can't offer a quality review as my only other experience is with the OEM pads at autocross. I can say that they never once faded, not in the slightest. The first stop when cold is a little weak but they are plenty warm after one good stop for the rest of the session. Not a terrible amount of brake dust. Rotors don't look excessively worn. Pad "feel" I would describe as "flat", there is not nearly as much modulation as the OEM pads offer and they just don't respond to subtle adjustments in pressure. You get used to it after a few laps making it easy to hit the same brake pressure over and over again, so that's a positive but it is difficult to finely adjust braking force if you are that kind of driver. Pad release is instantaneous (probably because they are a little loose...) and overall similar to OEM.

Overall they are a great value, pretty happy with em. Let me know if anyone has any questions and I'll do my best to respond.