Roamer

I have been reading the discussions and tech articles on installing 930 rotors on a narrow bodied car. However, most say to purchase an aftermarket remake of the 78-80 930 floating rotor.
My question is what is the exact difference with the 80-89 front 930 rotors? I know that they have additional spacing, but if this is a cast-in feature and I plan on using new wheels where I can compensate for the extra 25mm in spacing, why not just use the stock late-930 front rotors?

Just for clarification, I am planning on installing 993 front calipers and 965 rears to haul down a supercharged 911 Carrera.

Thanks as always for any insight.

Bill Gregory

From the VCI (www.vehiclecraft.com) website:

Why can't I go buy the complete used brakes off a 930 and bolt them to my 911?

Two problems. One, the front rotors available for the 81-up 930's are based on a "offset" hub design. If you were to bolt this rotor to your 911 hub, it would be off in alignment to the caliper by 22mm.

OK, why not just use the 930 hub then?

Because the hub is offset by 22mm to the outside, which would push your wheel out by 22mm (almost 1 inch) and, hence, fender clearance prevents that. Of couse if you've built a car with flared fenders you could do this, but the majority of you have stock fenders.....

And the second problem?

While the front calipers will bolt directly to a big-brake (3.5" mounting) front strut, and then work with our rotor set, the 911/914 rear trailing arm does not. The 930 rear caliper has the same 3.5" rear mounting as the front, but these trailing arms are made for 3.0" mounting. Some clever machining has to be done to the caliper to make it bolt directly up to the trailing arms. We then use a stock german 930 rear rotor, which fits the hub fine and the e-brake is retained (914 looses e-brake, however).

Roamer

Thank Bill,

However, as I stated originally, if I were to use 930 hubs and rotors with a new wheel having a ~50 mm offset, I "should" be ok, right?

Bill Gregory

The concern I would have is if the 81+ 930 turbo rotor bolts up to the hub and, due to the 22mm offset referenced above, puts the rotor 22mm off center of the caliper, that can't be rectified by wheel offset.

Roamer

So what you are saying is that the hub combined with the rotor will not rectify the offset concern and would leave the rotor ~22mm to far offset from the caliper?

Bill Gregory

Yes. You might want to call Doug at VCI and discuss it with him, or send him an email at doug914@optonline.net.

Roamer

Thanks again Bill. I may just go with the stock floating rotors from the 78-80. I was just trying to keep cost down.