How does a ROTOR go bad?

I was having a discussion with a local parts seller the other day... We were talkinga bout prices of parts for the 12A, and he mentioned that the rear rotor is a rare part because it is the first to go bad.

How exactly does a rotor go bad? The apex seal grooves might wear out, but that should be even with the front... The rotor bearing takes the wear of the eccentric shaft.

The only thing I can think of is the cases where you mulch an apex seal and it trashes the rotor... But it seems that there shouldn't be TOO many cases of that because it's more likely that the seal will trash the aluminium rotor housing before the iron rotor...

Maybe I should start collecting cores from the local scrap yards.

 

i know that the rotors can get too hot and collapse. other than that, all apex seal and side seal is usually even. its hit or miss which rotor goes bad first. perhaps being too lean or rich on one rotor. oil starvation to a rotor.

 

The myth about rear rotors going bad is due to 2nd Gen cars which rev limiter shut down injectors to the rear rotor - this certainly brought the engine revs down, but running it that lean also caused serious pinging which quickly trashed the rear rotor apex and side seals.

Rotors are interchangeable between front and rear, IIRC, so rotors don't really 'go-bad'. There's always a reason, like oil starvation, overrevving, or overheating.

 

12a's do have front and rear rotors. The 'bathtubs' are tapered, they are not symertical like the 13b's.

For some reason, which I haven't figured out yet, it seem that the rear rotor is more likely to throw a seal than the front one, regardless of which engine.