Custom Brakes: a hodgepodge of parts

I'm working on a custom solution because rear brakes for the FC rx7 because as of now they are NLA OEM & aftermarket. the autozone/rockauto special were getting bad lately anyways as tool life was coming to an end for these castings so I finally made some headway on using another cars caliper on my car but the question I have is, how much of "non contact" patch is okay?

there is about 1/8" of pad material that doesn't touch the rotor, eventually as the pad wears these unworn sections will eventually make contact with eachother and then wear themselves equally, so problem solved... right?

or am I enjoying the 4/20 holiday too much?

Setup: stock FC hubs, stock (or whatever aftermarket turbo brake rotor) FC rotor, Z32 calipers/pads, custom lines --> the bracket moves the caliper to the rear side of the knuckle:

Once the pads contact one another, they stop clamping. The un-rotor-contacted portion will not self clearance, as rhey dont move relative to a wear surface. Onlyin compression. 

The pads won't wear when they touch they will stop clamping.  That said it's doubtful 1/8" of pad would resist that compression without cracking and breaking off.   

I wouldn't worry about that much bad hang off.  Just plan to remove the pads and knock that material off as the pads wear.   

nocones said:

The pads won't wear when they touch they will stop clamping.  That said it's doubtful 1/8" of pad would resist that compression without cracking and breaking off.   

I wouldn't worry about that much bad hang off.  Just plan to remove the pads and knock that material off as the pads wear.   

 

that was my other idea, simple power abrasion and be done. 

Dusterbd13-michael said:

Once the pads contact one another, they stop clamping. The un-rotor-contacted portion will not self clearance, as rhey dont move relative to a wear surface. Onlyin compression. 

oh dur, good point. Maybe I am still a touch foggy haha

Why would the pads make contact? Is it a crazy thin rotor? Rockauto says 20mm discard thickness so I'd be surprised if they touched before you went backing plate to rotor face.

In reply to ian sane :

just overthinking things as usual. 

ian sane said:

Why would the pads make contact? Is it a crazy thin rotor? Rockauto says 20mm discard thickness so I'd be surprised if they touched before you went backing plate to rotor face.

Depends on both the pad and rotor thickness, the pads hitting each other before the pad is severely worn against the disc would be a pretty common scenario for a non-vented rotor, but a ventilated rotor may be thick enough to get away with it.

fidelity101 said:

In reply to ian sane :

just overthinking things as usual. 

Not necessarily a bad thing when it comes to brake modifications.

I have been told that you actually do want the pads to overhang the rotors, prevents a lip from developing on the rotor so you can't easily slide the pads out/calipers off.

In theory the pads may contact when worn a lot.  Or you could take the pads off when they are half worn or so and buzz the lip off.  Brake pad material cuts very easily with a file, too, would probably take 20 seconds a pad if you have the skills of a file.

Realistically, are you ever going to wear out rear pads?

I had a 944 turbo that an idiot put the wrong front rotors on and the pads had big time overhang. It looked like they could have been capable of getting to the point of the pads touching. Luckily the rotor was also too thin and the wrong offset so the inner side piston calipers over extended and jammed themselves up before that could happen.

Personally I'd want to find better fitting pads or modify those pads to not overhand. But realistically as long as you keep an eye on it it'll probably be fine.

In reply to dps214 :

When I worked at Audi we had a guy do his own brakes and did the same thing. Yikes. I just don't understand how you do this and not think something is amiss?

In reply to ian sane :

I had a customer with an A3 chassis Jetta TDI who had another shop do his brakes.  10.1 calipers/pads with solid 9.4 rotors.  When I first saw it the pads were touching.  Told him he needed brakes like now, and they were the wrong ones.  Guy took it back to the guy, saw it again 3 months later, solid 9.4 rotors again.

I can imagine the conversation going like:

"I need rotors for a 1998 Jetta."

"Is it an 8 valve?"

"(looks) Yep!"

I was racing an early TVR and it used calipers out of one of the early Austin Healeys, for which decent race pads were not available.  I converted to another caliper that had availability of competition pads (MGB) and had the issue of the pad extending a bit past the rotor (solid, not vented).  I had to bevel the top edge of the pads before use so that they could never meet at the tops as we are discussing (done carefully with mask in open air - this was back in the old asbestos days).