Need Help Identifying Floating Rotors

[RSnider]

Short explanation: I bought a Group 2 BMW E21 320i touring car several years ago. The car was built in the 70's to race in the ETCC. The origin of the brake rotors has always been somewhat of a mystery to me until I stumbled across some photos of the floaters from the Porsche 930. I haven't compared exact dimensions yet, but it looks nearly identical to the floating rotors used on the Porsche 930, except with a different (offset) hat, which got me wondering if my rotors were OEM Porsche. Just like the 930 front floating rotors, my rear rotors have 12 "dog slots"; however, my front rotors have 10 slots. Initially, I thought the rotors with 10 slots were possibly from the 993, until I realized the 993 floating rotors don't have open slots, just holes.

So my question is, did Porsche ever produce a floating rotor with 10 "dog slots"? Or was that simply a common design of that era? Are there any manufacturers that still produce that design?


For reference:

930 floating rotor - 12 slots:


993 floating rotor - 10 holes, no slots:

[Bill Verburg]

Originally Posted by RSnider

Short explanation: I bought a Group 2 BMW E21 320i touring car several years ago. The car was built in the 70's to race in the ETCC. The origin of the brake rotors has always been somewhat of a mystery to me until I stumbled across some photos of the floaters from the Porsche 930. I haven't compared exact dimensions yet, but it looks nearly identical to the floating rotors used on the Porsche 930, except with a different (offset) hat, which got me wondering if my rotors were OEM Porsche. Just like the 930 front floating rotors, my rear rotors have 12 "dog slots"; however, my front rotors have 10 slots. Initially, I thought the rotors with 10 slots were possibly from the 993, until I realized the 993 floating rotors don't have open slots, just holes.

So my question is, did Porsche ever produce a floating rotor with 10 "dog slots"? Or was that simply a common design of that era? Are there any manufacturers that still produce that design?


For reference:

930 floating rotor - 12 slots:


993 floating rotor - 10 holes, no slots:

The 993 rotor is not really a floating design

but yes, 930 from '78-80 used a 304x32mm floating annulus

here is a pic of one

[RSnider]

That's the same photo I posted in my OP (I snagged it from another thread on the forums).

[Bill Verburg]

Originally Posted by RSnider

That's the same photo I posted in my OP (I snagged it from another thread on the forums).

and it is an oe 930 floating rotor

[RSnider]

That much I already knew (I just included the photo as a reference for the number of slots). I still need to compare critical dimensions with my rotors are the OE porsche rotors to determine if they are, in fact, Porsche OE. Or at least the rotors with 12 slots.

Still no word if Porsche ever made a similar rotor with only 10 slots.

[safe]

Found these in an add, so I can't verify the information. Looks like 10 slots.


"380 mm floating 993 GT2 EVO rotors. The centers are Porsche Motorsport."

[Bill Verburg]

Originally Posted by safe

Found these in an add, so I can't verify the information. Looks like 10 slots.


"380 mm floating 993 GT2 EVO rotors. The centers are Porsche Motorsport."

This is the complete 380mm GT2 EVo front brake set up