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Craig, what rotor are you using? is it a brembo or copy, or something custom.
Is the hat hub centric? how is it centered.
since the hat is everything for the right offset for the 928, whether GTS, stock S4 or something larger like a 330/355mm rotor, do you have the larger rotors as well for this hat set up?
Craig's photo of the big blacks with the Girodisc rotor is from my car and that's a 993TT rotor. It's on my '79 with the special caliper mounting adapter from 928MS and was installed, inspected, and tested by Carl during the mechanical upgrade portion of my 928 Spyder build.
How I came to configure this setup is that Carl offered a kit to take my OEM '79 brakes up to those of an S4. In doing further research I learned that the caliper offset and mounting Bolt spacing and size of the S4 was exactly the same as for the larger big blacks on the GTS. Looking at rotor diameters and hat offsets that would then work with those led me to the specs of the 993TT rotor and to the 2-piece slotted Girodisc setup as the best one I could find.
So, what I can tell you is that because of the 928MS caliper mounting adapter, this setup goes together and works perfectly - rotor is properly centered in the caliper and rotor area swept by the pad is perfect (as you can see in the photo). What I can't tell you is whether this rotor with the offset of the hat for the 993TT works with a stock GTS as a straight rotor replacement. When it comes to stuff like this, Kibort is always right based on all his racing experience, so unless the 993TT rotor and hat dimensions are the same as those of the 964T, this may not work if not part of an upgrade to an older 928.
Understood. Hat section has a different offset than our GD 993tt rotor sets. Rotor itself the same. These are floaters. PM or e-mail for RL delivered pricing
Sorry Craig. In my post I hadn't read the info in this one carefully enough. So it now looks like you have a new product offering with a different hat for the 928GTS in addition to the 993TT setup I'm running. Nice work - now you should have both the upgrade fitment and the direct fitment options covered.
It's been said before, but it is very important to point out, even if it seems obvious:
1) Early 928s are Axial mount Calipers - therefore the adaptor has specific dimensions. This would require a specific offset for the rotor (custom hat, etc)
2) Late 928s have Radial mount Calipers. When you move from an S4 caliper to a "GTS/BigBlack/BigRed" caliper, you use a larger rotor.
When you use this "larger" Rotor - you need a specific offset. You can buy a 993TT rotor - BUT - you need a different offset than the hat that comes with the 993 TT rotor.
Good thread! Can any of you smart folks identify what I have here? I need rebuild kits for the Calipers, and a few hard service items for the rear right caliper, and front rotors.
Rear rotors are 993 rotors
I just blasted the entire unit to clean it up all at once as I hate working on dirty stuff.
Is there no one here that can identify my parts and assess why this happened? I certainly do not think a 2 piece rotor is a good design from the complete failure herein? I certainly thought there would be more astute and hands-on people here in Rennlist which offered assistance - even opinions!
09-03-2015, 02:08 PM
