Recently pulled the pads of our '80 280zx. The car is a Lemons race car and we've done one race on these pads (PBR Metal Masters.) When I pulled the rear pads I noticed that they are wearing at a strange angle, as though the pads are not being pressed perfectly parallel to the rotor. The "bottom" edge of the pad is significantly more worn than the upper edge, perhaps by as much as an 1/8" difference in pad thickness. Given that there is just the single large piston I have a hard time understanding how this is possible. Has anybody seen this before?

We are also trying to deal with a pretty large amount of pedal travel before the brakes seem to engage. I understand there is an adjuster on the back side of the MC which I'll play with. Does this just raise the brake pedal higher and lower off the floor, or does the pedal stay in the same place but the engagement point of the brake pedal changes? Don't think we have a bad MC, but that will be the next test if this adjustment doesn't do the trick.

 

Do the e-brake levers work on the calipers?

And yes, you can adjust the MC plunger.

 

Yes, the e brake works fine.

 

I've asked around a couple of other knowledgeable Z folks and it sounds like this isn't that uncommon but I need to double check that nothing is binding the piston. I'll do this.

Another thing I was suggested to check (in relation to a brake pedal which gets spongy even after thorough bleeding) is the gap between the piston of the brake booster and the "cup" of the master cylinder. How do I test this gap? And how do I set it to the correct size (not sure where this spec is)?

 

I'm seeing angled brake pad wear as well, as you can see in the photo.
This is off a 1983 280ZX NA, after running 2-3 races in the 24 Hours of Lemons.
Near as I can tell, this is caused by wear on the caliper slide pins and/or bores that the slide pins run through.
With enough wear, the two halves of the caliper can move enough to form an angle between them.