jc964rs

You can find drilled rotors for C2 / C4 at FVD. They are Zimmerman rotors

david@st ives

To the guy with the pulsing brakes i had the same problem as you ,
the problem was excessive rust build up on the inside of the rear rotors the outside was smooth ,i could not see it at first because it was mostly near to the hub .
The car had little use before i bought it and not been driven hard ,the caliper plates had gripped the pads like a vice due to plate corrosion and were well and truly clamped in there so the pads were not making contact on the inside of the rotor , so as i drove hard over a period of twelve months the pads were pushed closer to the rotor making the pulsing worse making the car really uncomfo rtable to drive , ie car shaking like hell under hard braking then pulsing as i braked lighter, the rust build up was up to about 5 mm
so before you think rotors are warped check for the rust ,not easy to see even with the pads out
cheers
dave

Bill Gregory

Joe,

What you described are several things: 993 C2 rotors are a different offset than 964 rotors. If you're using them, with 993 calipers, you may have rubbing on the interior wheel well, as they have several mm less offset than 964 rotors.

For 993 calipers mounted on a 964, the 928S4 rotors would be used. However, 928S4 brakes didn't come cross drilled, so, from Porsche, with 993 brakes mounted on a 964, you can use the very pricey (over $325 each) 968 M030 cross drilled rotors. Otherwise, as pointed out in another post, you can get cross drilled rotors from several non-Porsche sources, for around $110 each, as I recall.

Dunasso

Bill, more info on the use of 993 rotors on my 964 please. I know that there are after market companies that sell X-drilled rotors for 964. Unlike Porsche rotors, the aftermarket rotors are not casted with the holes, but are drilled, making the aftermarket rotors more subjectable to cracking. It is also a fear of mine that the aftermarket rotors are made of inferior materials that would allow for premature warping aswell. I may be misinformed here but I only want the best product for my 964 and would rather have 993 rotors. At the same instance, spending a bit more for a part that is known for it's quality is not beyond me.

So, in conclusion, if you know where we may find more information on this rotor swap and what's neccessary for it, I as well as others would be very appreciative.

Duncan

Bill Gregory

If you want cross-drilled rotors on a stock 964, the rears are easy - use Carrera RS rotors.

For clarity, 993 rotors cannot be used on a stock 964 (prior post updated).

993 calipers use wider/larger front rotors than 964's, and even with 993 calipers, the 993 rotors are the wrong offset for use on our 964's. If you want Porsche cross-drilled front rotors with 993 calipers, use the 968 M030 rotors.

Not all non-Porsche-supplied rotors are truly drilled, which I agree should be avoided. I believe Zimmerman's have cast-in holes, however, you should confirm that.

Marc Shaw

What about the cryogenically treated cross drilled rotors? Are they any better?

Marc

Bill Gregory

Marc,

I've found cryogenic processing makes a difference, and others in the 964 racing arena have found benefits, however, there are some who think cryogenic processing is nothing more than fairy dust or who have not realized benefits in their application. When I first went to 993 calipers, my first set of rotors were plain slotted rotors. I developed rotor cracking withing 3-4 tracks days of usage. I replaced them with plain slotted rotors that were cryogenically frozen, and have maybe 10 track days on them, with visible cracks starting to form. Based on my positive experience, I wouldn't, and don't, use cross-drilled rotors without cryogenically processing them.

For reference, the Porsche standard for tossing a cross-drilled rotor is when one of three conditions occurs: cracks exceed 7mm in length, cracks reach the edge of the rotor, or rotor wear exceeds the minimum thickness. A rule of thumb is if cracks connect holes, the rotor is also toast.

Marc Shaw

Other than what the seller says or advertises, any way to tell if they are actually frozen rotors or not? Is there a surface difference visible?

Marc

Bill Gregory

Diversified Cryogenics puts some heat sensitive paint on the rotors, however, beyond that, they look the same.

Marc Shaw

Thanks - I'll keep reading and learning before I buy any -- gotta upgrade the suspension first anyway.

Thanks....Marc

JoeW

Perhaps this is one reason there are spacers on the front.

I'll be taking the car in for some suspension analysis and "tuning" in tne next couple of weeks. I'll try to get some specific information on what is there then and will post it here.

As of now, I have the paperwork and receipts from the PO, and the description of the mechanic -- and it's probably obvious I don't have the technical background to get very specific on my own -- so while the suspension is apart it'll be pretty easy to get some details on the front brakes which for now have only been described to me as "993." You've got me curious.

Joe.

Dunasso

Thanks Bill, for making some sense out of it all, but I still have a few other questions that I'll put into a new thread.

Duncan