RX7 Front Two-piece Rotor
This tech tip was created due to OE manufacturing discrepancy between the hub surface and spindle mounting tab. See details here:
http://www.rx7club.com/showpost.php?p=6960449&postcount=453
The stock front rotor has a 22.0mm thickness with 6.0mm plate thickness.
The stock caliper can theoretically accept a 24mm rotor with a groove width of 25.4mm
When we design a two piece rotor, we typically add improvements to overcome some OE one piece rotor deficiencies, rather than just duplicating OE specs and reducing the rotor weight. On this rotor, we increased the rotor to 24.0mm with a 7.5mm plate thickness, which substantially increased the heat capacity for serious tracking, yet still with a weight saving of 2.3 lbs. per rotor. We have included this information of thickness change in our product description.
Be aware that the OE caliper is a mass production model, i.e. the groove was “casted” instead of machined, and has a side (axial) mount (like most Brembo OE calipers) instead of a radial mount. Because of this, it will tend to flex more.
Our two piece rotors are precisely machined and assembled to have the exact offset (from the hub surface to the center of disc) as one piece rotors, but unfortunately not the OE caliper. You can verify on your OE setup (with a 22mm stock rotor) that the caliper is not perfectly aligned with rotor. Since the rotor is only 22mm, you probably will not feel the deviation in alignment or the interference.
When we test mounted the two piece rotors, they fit fine, but when the car was under sharp turning or heavy braking, interference (due to the caliper flexing) might show up. This interference can vary from one vehicle to another; not all customers who installed our two piece rotors have experienced this.
After the rotors are installed, check with a feeler gage to make sure that the clearance between the caliper wall and rotor surface are even. Remove (by filing) or add (by using washers) to the caliper mounting surface as necessary to achieve perfect alignment (centering) for optimal results.