Question about Medium S4 brakes???
02-16-2007, 11:35 AM
#16
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Now were getting someplace. Great info guys thanks.
Actually the rear piston sizes for the 993TT big reds are 28/28mm vs. the 94 turbo 3.6 little reds are 34/30 vs the front 44/36 for both. I had been told that the reason for the smaller rear pistons is to adjust the clamping force to compensate for the larger 48 x 132mm pads and larger 322 x 24mm rotor vs the 44 x 98 mm pad and 299 x 28mm rotor used on the 94 turbo. Technically the rear 993TT rears are medium S4 calipers using smaller pistons and the same sized pad as the medium S4 fronts but slightly smaller pads than the big red fronts 58 x 132mm pads. This upped the pad area from 474 cm squared to 552 cm squared.
Originally Posted by atb
Something else to note.
I have the "big red" rear brakes (993TT), which use the S4 size calipers but... the piston sizes are way smaller. They are even smaller than the stock S4 rear pistons. So, you get a bigger caliper than stock, a bigger pad than stock, but smaller pistons. I don't understand why the big red rear brakes don't use the S4 pistons, any ideas?
I have the "big red" rear brakes (993TT), which use the S4 size calipers but... the piston sizes are way smaller. They are even smaller than the stock S4 rear pistons. So, you get a bigger caliper than stock, a bigger pad than stock, but smaller pistons. I don't understand why the big red rear brakes don't use the S4 pistons, any ideas?
02-16-2007, 11:58 AM
#17
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Correct on the 993TT rear calipers: They are not the same size as S4 or 951S calipers rear calipers. 951S front calipers ('88S & '89) = 928S4 calipers.
My '91 turbo came with big blacks (no raised lettering). As your picture (Anthony's 1st post, pictures 2 & 5 are both Big-blacks) suggests. I changed them out for Big reds just because my car is red (a garage with two red on black Porsches).
Erkka's 1st picture, 2nd caliper is not a front S4 caliper. It's a rear: look at how the metal shapes around the end of the word "Porsche". The metal shapes to almost a 45d angle.
Now look at my S4 caliper photos (both): Rear caliper shot (Anthony's first post, 4th picture) shows the same shaping, but my front caliper shot (Picture 3) shows barely any tapering towards the end of the caliper.
My '91 turbo came with big blacks (no raised lettering). As your picture (Anthony's 1st post, pictures 2 & 5 are both Big-blacks) suggests. I changed them out for Big reds just because my car is red (a garage with two red on black Porsches).
Erkka's 1st picture, 2nd caliper is not a front S4 caliper. It's a rear: look at how the metal shapes around the end of the word "Porsche". The metal shapes to almost a 45d angle.
Now look at my S4 caliper photos (both): Rear caliper shot (Anthony's first post, 4th picture) shows the same shaping, but my front caliper shot (Picture 3) shows barely any tapering towards the end of the caliper.
02-16-2007, 12:10 PM
#18
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Originally Posted by MarkRobinson
My '91 turbo came with big blacks (no raised lettering). As your picture (Anthony's 1st post, pictures 2 & 5 are both Big-blacks) suggests. I changed them out for Big reds just because my car is red (a garage with two red on black Porsches).
Mark,
Actually the 91-92 turbos used the medium S4 calipers with the slightly smaller 48 x 132mm pad and the same sized pistons and larger 322 x 28mm rotor the big reds/blacks were not offered until the 94 turbo 3.6 using a slightly different rotor same piston size and slightly larger 58 x 132mm pad. That was why I was confused by your pictures because I knew the 91-92 and 951 S calipers were all considered medium S4's and looked more like t he big red/blacks than the calipers you had pictured. Apparently there was a design change later on making all the calipers look like smaller big red/blacks. The (92) 93 GTS is still the first Porsche to use the big black calipers.
02-16-2007, 12:25 PM
#19
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big blacks
I'm 100% sure 91-92's came with big blacks. '91-92 rotors are interchangable with '94 rotors: '94 rotors are a different internal vein casting, but offsets/diameters are identical.
I sold my big blacks off my '91 turbo in '99 for good money as track calipers. All my brake resourrces for the last 8 years have told me the same thing. 94 3.6 had a much better ABS, big reds (in lieu of blacks), pad change, & differently veined rotors. Rear calipers/rotors are the same. I'll see if I can find some info to back up my claim.
Mark.
I sold my big blacks off my '91 turbo in '99 for good money as track calipers. All my brake resourrces for the last 8 years have told me the same thing. 94 3.6 had a much better ABS, big reds (in lieu of blacks), pad change, & differently veined rotors. Rear calipers/rotors are the same. I'll see if I can find some info to back up my claim.
Mark.
02-16-2007, 12:38 PM
#20
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Originally Posted by MarkRobinson
Erkka's 1st picture, 2nd caliper is not a front S4 caliper. It's a rear: look at how the metal shapes around the end of the word "Porsche". The metal shapes to almost a 45d angle.
GTS big blacks were first as they presented in late summer '91 even though first actual production cars were maybe made some months later. AFAIK they are last large Porsche brakes which are not monoblock design. Having these side by side with S4 fronts shows that difference is enormous. Same kind of jump in size as between 220 and 250 hp 951 have. Do have pic somewhere, just need to find it.
I also believe 3.3L 964 Turbo had S4 size brakes and not big blacks. Could be wrong though.
02-16-2007, 12:40 PM
#21
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Originally Posted by MarkRobinson
I'm 100% sure 91-92's came with big blacks. '91-92 rotors are interchangable with '94 rotors: '94 rotors are a different internal vein casting, but offsets/diameters are identical.
I sold my big blacks off my '91 turbo in '99 for good money as track calipers. All my brake resourrces for the last 8 years have told me the same thing. 94 3.6 had a much better ABS, big reds (in lieu of blacks), pad change, & differently veined rotors. Rear calipers/rotors are the same. I'll see if I can find some info to back up my claim.
Mark.
I sold my big blacks off my '91 turbo in '99 for good money as track calipers. All my brake resourrces for the last 8 years have told me the same thing. 94 3.6 had a much better ABS, big reds (in lieu of blacks), pad change, & differently veined rotors. Rear calipers/rotors are the same. I'll see if I can find some info to back up my claim.
Mark.
Sorry Mark but this I can prove 100 different ways that you are wrong. The 94 turbo was the first 911 to come with the big reds or blacks. The 91-92's used the 48 x 132 mm pad the 94's used the 58 x 132mm pads. I have worked on numerous 91-92 turbo brakes and have pads for both and they are different. The Porsche PET and Technik manuals for these cars will show the same. The 91-92 turbo came with part number 965.351.423(424).01 44/36 mm pistons using 965.351.043(044).00 322 x32mm rotor. The 94 came with part number 993.351.425(426).10 44/36mm pistons and 965.351.045(046).00 322 x32mm rotors.
This has been discussed in depth on the 964 turbo forum and is listed in every book from Paul Frere to Adrian Streather's 964 companion guide not to mention all the factory workshop manuals and technik information.
It is possible that your 91-92 turbo had been modified prior to your purchase but the brakes from the factory are medium S4's on the 91-92 turbos.
02-16-2007, 01:09 PM
#22
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brarkes
sure it's possible: it was my first big brake venture & I have not tinkered with early 965 brakes since then.
I knew pad sizes & such were slightly different, but if memory serves, I've seen many pad mfgr's list pads as the same for '91-94 911 turbos.
Oh well, at least I helped with the S4 caliper clarification. At least we know the mounting points on the 965 spindles are the same from '91-94.
I knew pad sizes & such were slightly different, but if memory serves, I've seen many pad mfgr's list pads as the same for '91-94 911 turbos.
Oh well, at least I helped with the S4 caliper clarification. At least we know the mounting points on the 965 spindles are the same from '91-94.
02-16-2007, 01:40 PM
#23
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Erkka wrote:
I still find it odd that the smallest piston on a stock rear S4 caliper (small 4 pot) would still be larger than the biggest piston on the a stock rear 993TT caliper(same size as front S4 size caliper and pad). Is the rear engine configuration of the TT factor perhaps?
It could be balance thing between front and rear brakes. There has to be some difference in force what comes out from piston at given pressure since there are large and small piston in each caliper. Reason given for this is that this will allow even pad wear. If it works within one caliper it should work between calipers also. Don't know how exactly Porsche wants to change front/rear brake ratio with that change though.
02-16-2007, 02:00 PM
#24
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Thread Starter
Originally Posted by MarkRobinson
Oh well, at least I helped with the S4 caliper clarification. At least we know the mounting points on the 965 spindles are the same from '91-94.
I started looking into different brakes used and all the different configurations depending on models and there is a ton of info. Mostly the info falls in model designation with little cross references between 911/944 or 928. Very confusing and hard for anyone to keep track of. Even after I thought I had done all the research needed you showed me there is even more out there that is not well documented. The differences between brakes can be subtle and to be honest for street applications a medium S4 or Big red/black will do the same thing and is overkill unless you race. Most of this comes down to cosmetics and the down side is added unsprung weight.
02-16-2007, 03:06 PM
#25
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Originally Posted by atb
Is the rear engine configuration of the TT factor perhaps?
02-16-2007, 03:16 PM
#26
Race Car
86 5-SPEED
My brakes are fine but have a little rotor shudder. I was thinking about putting some new pads on The $45.00 Mintex and grinding the rotors. For about $450.00 I can purchase a set of new rotors cross drilled. My ? is should I look into upgrading the calipers if so what type will provide a direct replacment with out all the mods. If I do go for new rotors will I get a good bang for my buck or simply change the pads will be about the same result. I don't plan to race this but want as much stopping power for the money spent. Any feed back?
02-17-2007, 01:00 PM
#27
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I haven't much more to contribute that hasn't already been said.
I have a couple pics of the Medium S4 brakes used on MY '86.5-87. The front shows the 42mm piston (bore) which was changed to 44mm in '88.
Regards,
Jim Doerr
'84 EuroS2, 5sp
"Chewy"
I have a couple pics of the Medium S4 brakes used on MY '86.5-87. The front shows the 42mm piston (bore) which was changed to 44mm in '88.
Regards,
Jim Doerr
'84 EuroS2, 5sp
"Chewy"
04-18-2007, 09:44 PM
#28
Originally Posted by Vilhuer
Reason why its difficult to mount 996 GT2 or GT3 calipers into 928 which use medium or big black calipers.
But this also proves the ability to put GT calipers on the spindles of 78-86 928s, because of the axial-to-radial mount adapter. Cool.
11-12-2016, 10:40 PM
#29
After some helpful clarification from Mark regarding the S4 brakes he has for sale I find there are contradictions in many articles and info I have regarding the Medium S4 brakes used on the 928 S4 and other models.
I have seen 90 GT's and some S4's with brakes that look almost Identical to the big blacks used on the GTS. The differences are smaller rotors and slightly smaller size of the caliper. I believe the length was the same but the width is different. These calipers used the 48 x 132mm pad vs the 58 x 132mm pad of the big black/reds. The medium S4 calipers are also noted as the same calipers used on the 91-92 turbo and the 993.
According to the article on Brakes written by Bob Gagnon and Bill Gregory there were 3 versions of brakes supplied by Brembo in the mid 80's:
"Brembo provided four piston calipers, with different sized piston sizes through 1998: The smaller of the calipers, introduced on the 1985 944 Turbo, the medium S4 caliper introduced on the 1986 Porsche 928S4 and the large "Big Black" calipers introduced on the 1992 928 GTS (also used in red color for 911 Turbo applications) The calipers use two sizes of pistons in each caliper half, which reduces taper, or uneven brake pad wear, that can occur when equal pistons are used.
.....The Carrera RS and Turbo 3.3 used Medium S4 calipers in front and small calipers in rear, while the turbo 3.6 carries Big Reds in front and medium S4's in back. Note the medium S4 black calipers used on the front of the 993C2 and Carrera RS/Turbo 3.3 are different castings, to work with respective 304mm and 322mm discs."
So now the confusion. There appears to be a conflict with this info whcih has been corroborated by many experts. The pictures I have show the medium S4's used on a 951 S which is the same Medium S4 used on the 91-92 turbo yet the pictures Mark has differers.
Can people corroborate and post pictures showing that the Medium S4 used on the 928 is a different casting than those used on the other models and if that is the case can anyone measure the pads used to see if they measure 48 x 132mm.
I am posting 5 pictures the first is of the small 944 turbo brembo caliper the second is of the medium S4 caliper used on the 944 turbo S then followed by the medium S4 calipers as seen on Marks S4 and the last are the big blacks.
Any clarification would be appreciated.
Thanks
I have seen 90 GT's and some S4's with brakes that look almost Identical to the big blacks used on the GTS. The differences are smaller rotors and slightly smaller size of the caliper. I believe the length was the same but the width is different. These calipers used the 48 x 132mm pad vs the 58 x 132mm pad of the big black/reds. The medium S4 calipers are also noted as the same calipers used on the 91-92 turbo and the 993.
According to the article on Brakes written by Bob Gagnon and Bill Gregory there were 3 versions of brakes supplied by Brembo in the mid 80's:
"Brembo provided four piston calipers, with different sized piston sizes through 1998: The smaller of the calipers, introduced on the 1985 944 Turbo, the medium S4 caliper introduced on the 1986 Porsche 928S4 and the large "Big Black" calipers introduced on the 1992 928 GTS (also used in red color for 911 Turbo applications) The calipers use two sizes of pistons in each caliper half, which reduces taper, or uneven brake pad wear, that can occur when equal pistons are used.
.....The Carrera RS and Turbo 3.3 used Medium S4 calipers in front and small calipers in rear, while the turbo 3.6 carries Big Reds in front and medium S4's in back. Note the medium S4 black calipers used on the front of the 993C2 and Carrera RS/Turbo 3.3 are different castings, to work with respective 304mm and 322mm discs."
So now the confusion. There appears to be a conflict with this info whcih has been corroborated by many experts. The pictures I have show the medium S4's used on a 951 S which is the same Medium S4 used on the 91-92 turbo yet the pictures Mark has differers.
Can people corroborate and post pictures showing that the Medium S4 used on the 928 is a different casting than those used on the other models and if that is the case can anyone measure the pads used to see if they measure 48 x 132mm.
I am posting 5 pictures the first is of the small 944 turbo brembo caliper the second is of the medium S4 caliper used on the 944 turbo S then followed by the medium S4 calipers as seen on Marks S4 and the last are the big blacks.
Any clarification would be appreciated.
Thanks
thanks
11-12-2016, 11:58 PM
#30
Rennlist Member
You could just buy a set of 993 calipers and use them. That's what I did with my 81 as S4 brakes were more expensive at the time.
The bolt holes are the same so the bolt right in, just keep in mind the pistons in the rear are 20% bigger so you could change your brake bias valve to the 33 bar one and get some greatly improved braking power.
The bolt holes are the same so the bolt right in, just keep in mind the pistons in the rear are 20% bigger so you could change your brake bias valve to the 33 bar one and get some greatly improved braking power.