ilko

I got my hands on a pair of 928 S4/944 Turbo S front calipers.

From what I understand they are the same size as the 993 front calipers and use the same size 304x32mm rotor. Can I use the 993 rotor on my 964?

On the other hand, these calipers are not the "Big Black" 928 calipers that I can use with the 965 rotors, so I'm not sure if I will get a noticeable upgrade from my stock brakes.

My car is set up for DE/Street and I'd like to know if I should use them, or sell them...

All opinions are welcome

Jamie Summers

You can't use the 993 disc, the offset is wrong. You need the 928 S4 disc (solid) or 968 MO030 disc (drilled). The 968 disc is REALLY expensive for some reason, so I went for Zimmerman drilled aftermarket discs and sprayed the hubs grey to stop the rust. NB you still need the adaptor bracket to change from axial to radial (or the other way - can't remember !)

Personally I think it's a worthwhile updgrade. If you also do the rears (with 993 calipers) go for the RS or Turbo proportioning valve, decent pads,fluid and hoses, you will never suffer from brake fade ever again, no matter how hard you abuse them.

Jamie

ilko

Thanks Jamie! I have the axial to radial adapter, I'm just not sure whether I should stick with the 928 S4 brakes or go with the Big Blacks and 965 rotors. The 928 S4 rotor is slightly larger than the stock 964 rotor (304x32 vs 298x28 -> only 6mm difference). The 965 rotor or on the other hand is 322x32 which is almost an inch bigger in diameter...

cobalt

Pros and cons to both, Bill Vandenberg knows this stuff better than anyone but the Medium S4's should be an improvement for several reasons. The pad size is increased from 44mm x 98mm to 48mm x 132mm. This is just 10mm narrower than the big red/blacks. Piston sizes also increase from 40/36 to 44/36 (same size as the big reds) and your increasing your rotor size from 298x 28mm to 304x 32mm.

So yes it should help on the track. One positive side is the components weigh less than the big red/blacks. So you are gaining clamping force, larger pad and rotor for better heat dissipation with less unsprung weight.

i have the big red upgrade and it is very nice but I find it overkill in a 964. Both my wife and I drive the car on the track and I have yet to have any fade or need to bleed my brakes between several events. That is with 8 runs a day for 3 days in a row. So you should do fine with these.

ilko

Thank you Anthony, I didn't take the size of the pad into account and the fact that this set up is actually lighter than the big blacks. Thanks again

Ruairidh

[QUOTE=cobalt;4631399] So you are gaining clamping force, larger pad and rotor for better heat dissipation with less unsprung weight.

[QUOTE]
Which is also exactly why I went the S4 route with my recent brake job.

Also bought Zimmermans and also recommend spraying the hats....

Bill Verburg

Who's that?

Excluding some very rare and funky early 928S4 calipers, the most common 928S4 front caliper is essentilly the same as a base 993 front caliper when the bleeds and feeds are swapped. Both use the medium/large size 132x48mm pad, 36/44mm pistons, radial mount caliper for 32mm wide and 304-322mm rotors.

a base 993 rotor won't work unless you swap in the 993 uprights too.
For use w/ the common axial to radial caliper adaptors use either a 965 3.6T rotor or 928S4 rotor depending on the adaptor. The 928S4 rotor is a 1 piece 304x32 design, the 965 is 322x32 , obviously the 322mm rotors need a taller adapter than the 304mm rotors. For most people w/ a stock 964 the 304x32 rotors are enough the RS did use the 322s and that is wwhat I would try to emulate if it was my car. The 322s are more than enough rotor for almost any purpose.

the 968 M030 disk usually referenced in this context is the x-drilled rear rotors. They are the same size as stock 964 or 993 rears just x-drilled.

ilko

Thanks Bill! Any idea where I can get the taller adapter?

Bill Verburg

If you want to use the 322mm rotors w/ 993/928S4 calipers you can probably get adapters from VCI. Their usual adaptor is for mounting Big Reds, that won't work w/ the shorter 993/928S4 caliper. You'll need to explain what you want to do.

ilko

I spoke w. Doug at VCI and he suggested that I go with the 928 S4 rotors. He said the 965 rotors don't fit under the 928 calipers. They are just too big. If I were to use a longer adapter it will work but I won't get the pads to bite the entire surface of the rotor and that defies the purpose of going with bigger rotors.

So I'll just go with the 928 S4 rotors.

Thanks for your help guys

Bill Verburg

That's not true at all the 964RS, 964 America roadster and the 964 t/l all used that size caliper w/ the 322x32mm rotors. There were at one time 3 different caliper adapters available to use the 322's. 3 different versions were needed because the 964RS & 965 3.3 caliper has the extra spacer built into the mounting bosses. The 993/928S4 caliper needs the extra tall adapter and the big red caliper itself is ~10mm taller so needs a shorter adapter.

Never the less the 993/S4 on the 928 rotors is still a very good choice. You should also use small 993 30/34 rear caliper to replace your small 28/30(unless you have a C4t/l in which case you already haave them).

Bill Verburg

one more thing, you can also update the front end to 993 spec, no adapters needed.

ilko

Thanks Bill! Do you know the exact parts I would need to replace to get it to 993 spec?

Bill Verburg

uprights, tierods for sure

ask Geoffrey about struts, though most people that are doing this upgrade will want struts any way

Bill Verburg

Further discussion here