Prospeed_Motorsport

Ooops. Just read a couple more posts. If the calipers came froma 928 S4 and were stock, they are NOT the big reds/blacks. They are the "S4" caliper and will use the same rotor as the 951s or, if you want factory x-drilled, the 968 M030 front rotors. The dimensions on these rotors FWIW are 302 x 32 mm

JC951

^ does the s4 caliper look like a big black then? because my caliper looks like a big black...i will probably be with my car for a little while today...maybe i will take the wheel off and get some sort of accurate measurement of the size of the rotor. I guess that should help in seeing which rotor to get

Prospeed_Motorsport

Other than the phyiscal size of the calipers, they look identical and they both bolt up to the same M030 spindles or aftermarket caliper adapters. Assuming the rotor is the correct size, it should fill the caliper completely, then measuring the rotor should tell you which caliper you have.

HTH

JC951

outside diameter?

Prospeed_Motorsport

The S4/951S/968 M030 front rotor is 302 x 32 mm (11.889" x 1.259") The 928 GTS/993TT rotor is 322 x 32 mm (12.677" x 1.259")

Nurburger

If you take your wheel off, post the serial numbers on the backside near the center bore - we can work out your offsets.

JC951

i will see what i can find

333pg333

Justin I'm betting you have what we call the 'Medium Blacks' off an S4. Do and Advanced Search for 'Brakes' under user name Olli Snellman and sift through his threads. I'm sure you'll find some pics of all the callipers grouped together on the floor. You can see the difference. I'd look it up if I had time.

Here's a good reference list to. Save it for the future, it comes in handy.

http://www.pelicanparts.com/MotorCity/wmv/brakes.htm


EDIT: Here's a link to a thread with some input / pics from Olli.
https://rennlist.com/forums/944-turb...on-951s-2.html

JC951

the number i pulled off the back of the wheel was 90523-2...at least thats what it looked like to me. Also the calipers are 4 piston and somewhere about 11 inches long from tip to tip. the rotor fills up the whole caliper. I made a nifty little cardboard measuring device...i was bored, the rotor is 322mm. So now that we know that measurment, i'm guessing I need to get 928 GTS rotors for the front and pads as well

edit: thanks pat, i didnt refresh before i posted. on a side note, did the speaker grilles arrive yet?

333pg333

Yes thanks they did Justin.

Prospeed_Motorsport

As the rotor was 322 mm dianeter then you have to have the blacks from a 928 GTS as the S4 caliper will not fit that rotor. So now you ya know.....

FWIW, of the 2 piece (pre-boxster and pre 996) 4 piston calipers there were only 3 sizes for the fronts. There are:

The standard small front as used on the 944T (non-s), 944 S2 (non M030), 968 (non-M030) and 964.The early versions had rasied letters with 38 & 36 mm pistons, used scrapper rings rather than dust boots. In 87 this caliper lost the rasied letters and simple had painted "Porsche" and the piston sizes changed to 40 & 36 mm. This caliper is also an axial mount and fits a rotor of 298 x 28 mm.

The "middle" size (athough prior to 333pg333 reference I had never heard them referred to in that manner) is the S4 caliper. It first arrived on the 928 S4. The earliest ones in 86 (pretty rare) also used scrapper rings but did not have rasied letters. All 87+ have dust boots. The piston sizes are 44 & 36 mm. The S4 caliper was stock on the 928 S4, 951S, 944 S2 M030, 968 M030, 964T and 993. This is a radial mount calipers and fits a rotor of 302 x 32 mm.

Finally there is the Big Red (also available in black, yellow and silver) Although it debuted on the 93 928 GTS most tend to think of them as debuting on the 96 (or was the first year 97? I forget) 993tt. It is also a radial mount caliper, has dust boots, uses 44 & 36 mm pistons and fits a rotor of 322 x 32 mm.

HTH.

Michael

JC951

Now where can I get a decently priced slotted rotor as i'm going to be starting to DE and autocross the car?

samluke

I have used cross drilled ones. Factory. But I also need to know the hat to friction surface to know which ones

333pg333

Justin, this is the question that is appearing on a few threads at the moment. There isn't one made for this size. The easiest would probably be to buy the Vented full face GTS rotors and have someone route a few slots in them. I'm not sure if there is anything wrong with this theory as it seems too easy. I am also finding out from PFC if they do anything for this size too. It will no doubt be a 2 piece setup which has the benefits of being lighter (less unsprung mass is always good). I will confirm when I know. The 965 cross drilled ones are cheap and do perform well. Just that they do crack. Doing DEs shouldn't be too hard on them though so this could be a good stop gap solution. Pad choice will have an effect too. As will cooling the rotor. If you can fit some tube duct it's worth it, otherwise there are the deflector plates from the 968CS (I think).

333pg333

Richard, there is a small lip that is above the friction surface but before the hat itself. It looks part of the hat but I want to know that hat height too. Either including or excluding the lip.