928 S4 brake question

[Jeff Alton]

I have done lots of searching in the archives but still have a brake question. Lets say I have a pair of 928s4 front calipers and I want to put them on my 84 carrera. I also want to keep 16 inch wheels. Fronts are 16x7 911 part numbers (not the 951 with more clearance). What rear caliper would I use? What rotors would work front and rear and where do I get the rotors and lines? Do I need the 23 mm (or is it 23.3) master cylinder? Is this more trouble than it is worth or should I just buy a complete kit from VCI and sell these calipers?

Thanks, Jeff

[H20911]

sell and get a kit.

[lin7310948]

i have a 71 coupe...rs clone...with S4 front brakes and 930 turbo rear brakes.... s4 fit with 951 front wheels with no problem with clearance. you will need to reconfigure your front rotors for proper offset as well as proper thickness for the front caliphers. the 930 turbo rear caliphers will need to be modified to fit your trailing arms 930 rear rotors fit fine. i used a 23mm master cylinder...brake lines were easy to
rework....i am very pleased with my brakes as a system but if i were you i believe that i would just buy a proper kit and not hunt up, match up, and machine up a system.
i tend to agree with watercooled911!

[jester911]

You should talk to Bill Verberg on this board. He is the porsche brake guru. He will probably chime in but if he doesn't you should email him. I sure he can put you on the best path.

[Jeff Alton]

Thanks, just sold a set of 930 rears!! Ooops. Sounds like a kit is probably the best way to go.

Jeff

[ChrisBennet]

The S4 upgrade is expensive and it still won't fit in "911" Fuchs. The killer is the front brake rotors which easily cost more than the calipers - if you can find them. Then there are the hub adapters....
I had this setup and it worked with 7x16 944 Turbo Fuchs in front but just barely.
It does work pretty great though...
-Chris

[Jeff Alton]

Hmm, I am kinda interested in the idea of putting the 4 piston 964 calipers front and rear on with the 28mm thick front rotor. VCI makes this setup work and it seems like a reasonable upgrade.

jeff

[Bill Verburg]

I am kinda interested in the idea of putting the 4 piston 964 calipers front and rear on with the 28mm thick front rotor. VCI makes this setup work and it seems like a reasonable upgrade.

It's kind of expensive for what you get, the S4/930rotor front and 965/930 rotor rear is a nice package, 993rear can be subbed for 965 caliper rear w/ some additional effort.
You will need a ~7mm spacer front w/ 911 7x16s

All in all a kit is the best way to go, A few are buying the Brembo GTP or light kit and I am sure will report shortly.

I also recently saw someone advertising 4 wheel Stoptechs for early 911s.

[Jeff Alton]

Thanks Bill, I will go the kit route probably for sure. What are your thoughts on the 964 caliper front and rear with the front 28mm rotor that VCI sells? cars weighs about 2400 and sees a dozen DE's a year.

Jeff

[JeremyD]

I am Very Very happy with my S4 (993 stock) brakes calipers front, 993 stock brakes rear. my fronts are custom hats wilwood 309x32mm.



rears are 993 calipers with the throats enlarged for 930 stock rotors.

I think the kits are pretty exclusive - I just didn't want to part with all that green (and still use 16" fuchs!)

The good news is that I just bought some 16" bbs wheels and they fit nicely over my brakes too!

Have you looked at the 951 (944 turbo) VCI kit? I was going that route at first but didn't want to use a spacer. The 944 turbo rotors are much cheaper than the custom ones.

[Jeff Alton]

Jeremy, that is the kit I am referring to at VCI, uses 964/944turbo calipers. The spacer is for the wheel bearing and apparently there is some minor "issue" with the rear pads, but I am not sure excactly what that is. They are a little slow to respond to emails.

Jeff

[JeremyD]

You have to cut down the rear pad a liitle for clearance. Chris Streit is using the 944t/VCI version with good results. You might shoot him a PM - he was very generous answering a few questions that I had. 205/50 front tires should have no issues - 225 you start running into some clearance issues with either set up when you start spacing out the fronts to clear calipers...

[Jeff Alton]

Thanks

[Bill Verburg]

Jeremy, that is the kit I am referring to at VCI, uses 964/944turbo calipers

No it is not! Jeremy has 993f/r calipers on 304x32 and 309x28 930 sisized rotors. They are a big step up from the 964 setup you referrred to.

You might want to read this

[JeremyD]

Originally posted by Jeremy964

Have you looked at the 951 (944 turbo) VCI kit? I was going that route at first but didn't want to use a spacer. The 944 turbo rotors are much cheaper than the custom ones.

I think he was referring to this part Bill... To me the VCI kit seemed like to many compromises - rear stock rotor so have to monitor wear - cutting the pads - front was marginally bigger. I think the lighter cars (like Chris Streit) can get away with this - not sure about some of the heavier - bigger brake requirement cars...

[Jeff Alton]

I was refferring to the VCI kit. Hmmm, so what am I left with? The full 930 package? If I go the route Jeremy went, do I need the 951 front 16x7? Jeremy, is the package you got still available from your source?

Thanks, Jeff

[JeremyD]

The guy that I got my kit from told me he tested it on several different 16" fuchs and they all fit - not sure the sizes he tried though.

[Rufblackbird]

would 928 S4 rear calipers work on the rear, or would it have to be only the 993 or 965 rear calipers?

After reading this thread I'm definitely thinking about selling my frt & rear S4 calipers...

[JeremyD]

the 965 works the best because you don't have to open up the throats. They are much more rare and tend to be expensive. The 993's are pretty plentiful. The 993 rears are almost as good but require a little more work. The good thing with the 930 stock rear rotor is you maintain the stock emergeny brake.

Quoted direct from Bill Verburg's website = 993/S4 44/36 calipers w/ ~132x48mm pads for ~125cm2/caliper pad area can by used with the 304x32 mm rotors described above, these calipers work best with properly matching 30/34 w/ ~98x44mm pads for ~86cm2/caliper pad area rear calipers though they can be used with the 30/28 rears which use the same 98x44mm pads, either on the 930 309x28mm rotors. Care should be taken as this later setup is a bit front biased, again this is a personal issue but many road racers prefer it. The 2 sources of the 30/34 rear calipers are 965 rear which has the correct wide throat for the 28mm rotors or 993 rear which unfortunately has a narrow throat and will need modification to fit on a 28mm rotor. A 930 23.81mm boosted mc or the 23 mm non-boosted m/c are required for this setup.

There are several different versions of the 993/S4 caliper the correct ones for front use are the radial mount versions from the front of a 993. These will have the desired 44/36 mm pistons, all they require for mounting on a 911 is the proper transverse to radial mount adaptor available from various vendors. The true S4 front caliper while also radial mount is designed for a trailing mount position i.e. behind the axle centerline rather than the leading mount position as used on all 911 models. This means that the bleeder and transfer tubes must also be changed to implement front mount positions.

There are also transverse mount versions of the 993/S4 caliper, these were used on the rear of 993RS and 993S cars. These calipers can be used most effectively on the rear of a 911 with the previously described 993/S4 front calipers or with the Big Reds described in the next section.

IMO the best setup for most of us is the 993/S4 front calipers on 304x32 floating rotors used w/ 965 rear calipers on 309x28mm rotors. These provide a sweet spot where weight , thermal/mechanical reserve, bias, and size are all balanced w/ each other to provide more than adequate stopping power.

[Bill Verburg]

This is the VCI 964/944 kit w/ the smaller 28mm and 24mm rotors

Here are VCIs 993 on 930 size rotor upgrades

The guy Jeremy bought his from seems quite credible goes by the name DinFtown here is his site

The new Brembo GTP light kits sem like a good solution for lighter cars under say~3k#