6 Piston GT2/GT3 calipers are here!!
04-16-2011, 02:15 PM
#61
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I just don't understand why you guys keep writing we do not need them. You are so right ! I don't need either a 3.0 liter turbo engine iam currnetly building. For me and also for my friend Pete these cars are just a hobby. We would like to modify them to the direction we would like them to be. 951's are not so rare, so they should leave factory original. If so, i just can quit car hobby and start to collect stamps insteadt of it.
Awesome. Porsches are meant to be improved tastefully to the limit.
amazing when people sometimes forget that. sorry, but a 1988 Ruf Yellowbird is better than a 1988 911 Turbo, and so on. big brakes stuffed inside a beautiful set of 18" Speedlines? a 944 that can go 170 mph +? yes !
04-21-2011, 12:44 AM
#62
Three Wheelin'
Just going to throw this question out there, but if you're going to build adapters, why not look into C5 Corvette rotors/calipers? Super cheaper, ~250 for 2 NEW calipers, less used. Rotors are $50 a piece at any AutoParts store in America. They're 2 pot floating calipers, not fancy 4/6 pots, but that's the only "downside" I can see.
Might run into the same issue you did with the Q7 rotors though, the hats aren't very deep, but perhaps the difference in caliper design will give you some extra room?
Might run into the same issue you did with the Q7 rotors though, the hats aren't very deep, but perhaps the difference in caliper design will give you some extra room?
04-21-2011, 12:46 AM
#63
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Just going to throw this question out there, but if you're going to build adapters, why not look into C5 Corvette rotors/calipers? Super cheaper, ~250 for 2 NEW calipers, less used. Rotors are $50 a piece at any AutoParts store in America. They're 2 pot floating calipers, not fancy 4/6 pots, but that's the only "downside" I can see.
Might run into the same issue you did with the Q7 rotors though, the hats aren't very deep, but perhaps the difference in caliper design will give you some extra room?
Might run into the same issue you did with the Q7 rotors though, the hats aren't very deep, but perhaps the difference in caliper design will give you some extra room?
Some of us want to drive Porsches. if we wanted a Corvette, we'd buy Corvettes.
04-21-2011, 12:51 AM
#64
Three Wheelin'
Not trying to start a Corvette vs Porsche war, just stating that if someone wanted to try it, then it's an option. I'm sure track junkies would love $50 rotors and a pad selection that rivals the woman's aisle at the supermarket.
04-21-2011, 02:34 AM
#65
Marc,
Cayenne rotor is not the same as GT3 one what comes to the dimensions.Cayenne rotors are either 330mm or 350mm but rotor ET is different compared to GT3 ones.
If they were the same, a lot of GT3 owners would use Cayenne rotors because they cost about 1/4 price compared to GT3 ones. I suppose you have two alternatives:
1. Buy GT3 rotors
2. have a custom made hubs to accept Cayenne rotor with your caliper/adapter combo
The latter alternative is far more expensive for the start, but will be cheaper in the long run
Cayenne rotor is not the same as GT3 one what comes to the dimensions.Cayenne rotors are either 330mm or 350mm but rotor ET is different compared to GT3 ones.
If they were the same, a lot of GT3 owners would use Cayenne rotors because they cost about 1/4 price compared to GT3 ones. I suppose you have two alternatives:
1. Buy GT3 rotors
2. have a custom made hubs to accept Cayenne rotor with your caliper/adapter combo
The latter alternative is far more expensive for the start, but will be cheaper in the long run
04-21-2011, 11:08 PM
#66
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Hey Olli,
The GT3 guys ARE using the Cayenne/Q7 rotors. In fact I spoke with 3 guys today at the track that are using them. The secret is out.
Your second idea made me think about shaving 5mm from the hub face. I have asked Doug for his thoughts on this work around.
Scott, you are absolutely right on the vette rotors. There are several instructors that I run with quite a bit that have C5s and they can't stop their cars with the oe calipers, but they always tell me how cheap the rotors are!!
Marc
_____________________
'00 Audi TT
'99 996 (Wife's ride)
'86 951 LS1 (C-2)
'77 911 3.2 (C-1) Gone but not forgotten.
3.2 Conversion and 915 Rebuild Home Page
The 958 Conversion
958 Track Video
PCA National Registry of Instructors
The GT3 guys ARE using the Cayenne/Q7 rotors. In fact I spoke with 3 guys today at the track that are using them. The secret is out.
Your second idea made me think about shaving 5mm from the hub face. I have asked Doug for his thoughts on this work around.
Scott, you are absolutely right on the vette rotors. There are several instructors that I run with quite a bit that have C5s and they can't stop their cars with the oe calipers, but they always tell me how cheap the rotors are!!
Marc
_____________________
'00 Audi TT
'99 996 (Wife's ride)
'86 951 LS1 (C-2)
'77 911 3.2 (C-1) Gone but not forgotten.
3.2 Conversion and 915 Rebuild Home Page
The 958 Conversion
958 Track Video
PCA National Registry of Instructors
04-26-2011, 12:06 PM
#67
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"Here are the piston area numbers and why the OE 951 M/C works with the GT3 front and rear calipers.
Non S piston size: 36/38 front, 28/30 rear. Front/Rear ratio 62/38. Total piston area: 13898.44 sq/mm
GT3 size: 28/32/38 front, 28/30 rear. Front/Rear ratio 66/34. Total piston area:15506.92 sq/mm.
S calipers: 36/44, 28/30, 66/34, 15444.12"
Actually only the early 951's had the 36/38 mm fronts. When Porsche changed the caliper design to that of the dust boots (I believe this was with the 944 S2 but could have been earlier) the piston sizes increased to 36/40. Taking this new size into consideration the total piston area is 15041.26 sq/mm.
Several years ago I calulated the differences in clamping force and f/r brake bias (with stock 951 M/C) for the various conversions. If I can find the spreadsheet I will post. Bottomline is there really isn't much difference between the 6 pistons calipers and the small 4 piston calipers. And I will be the first to admit the big 6 pistons look astounding (IMHO) behind a set of 5 spoke, open wheels. That said, what folks seem to often forget is the objective is to use the SMALLEST caliper possible and vent the thing like crazy so you keep the unsprung weight to a minimum.
Non S piston size: 36/38 front, 28/30 rear. Front/Rear ratio 62/38. Total piston area: 13898.44 sq/mm
GT3 size: 28/32/38 front, 28/30 rear. Front/Rear ratio 66/34. Total piston area:15506.92 sq/mm.
S calipers: 36/44, 28/30, 66/34, 15444.12"
Actually only the early 951's had the 36/38 mm fronts. When Porsche changed the caliper design to that of the dust boots (I believe this was with the 944 S2 but could have been earlier) the piston sizes increased to 36/40. Taking this new size into consideration the total piston area is 15041.26 sq/mm.
Several years ago I calulated the differences in clamping force and f/r brake bias (with stock 951 M/C) for the various conversions. If I can find the spreadsheet I will post. Bottomline is there really isn't much difference between the 6 pistons calipers and the small 4 piston calipers. And I will be the first to admit the big 6 pistons look astounding (IMHO) behind a set of 5 spoke, open wheels. That said, what folks seem to often forget is the objective is to use the SMALLEST caliper possible and vent the thing like crazy so you keep the unsprung weight to a minimum.
04-26-2011, 01:48 PM
#68
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You are absolutely right on the clamping force and using the smallest caliper, etc. In my situation, the '86 front rotor/caliper set up was not designed to stop my car at the speeds that I achieve at the track. I have full ducting and huge Wilwood four piston calipers and I am eating rotors at the rate of 3 sets per season. In addition, I am using 93 or 83 compound PF pads which do stop the car as well as can be expected given the pad size, but add to rotor wear and brake fluid heating.
I have run out of '86 spindles and the used market is slim and often in poor shape so I'm going to the late offset. The options are to go with Big Reds, or the GT3 calipers. The Big Red pads are much smaller than the GT3 pads and the rotors are smaller and 3x the cost of the Cayenne rotors. The weight difference is slight. I can tell you from chasing a bunch of GT3s that they can stop like there is no tomorrow and they can do it over and over again . . . I'm just trying to even the playing field
Marc
_____________________
'00 Audi TT
'99 996 (Wife's ride)
'86 951 LS1 (C-2)
'77 911 3.2 (C-1) Gone but not forgotten.
3.2 Conversion and 915 Rebuild Home Page
The 958 Conversion
958 Track Video
PCA National Registry of Instructors
I have run out of '86 spindles and the used market is slim and often in poor shape so I'm going to the late offset. The options are to go with Big Reds, or the GT3 calipers. The Big Red pads are much smaller than the GT3 pads and the rotors are smaller and 3x the cost of the Cayenne rotors. The weight difference is slight. I can tell you from chasing a bunch of GT3s that they can stop like there is no tomorrow and they can do it over and over again . . . I'm just trying to even the playing field
Marc
_____________________
'00 Audi TT
'99 996 (Wife's ride)
'86 951 LS1 (C-2)
'77 911 3.2 (C-1) Gone but not forgotten.
3.2 Conversion and 915 Rebuild Home Page
The 958 Conversion
958 Track Video
PCA National Registry of Instructors
05-14-2011, 11:16 PM
#70
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Update . . . everything worked out after all. We had to go through one mock up to get the adapter right, but the corrected version is on it's way. The conversion will use the Cayenne/Q7/996 GT3 rotors and the 996 six piston calipers. Wheel studs need to replaced with the longer version if the car is used on the track.
Marc
_____________________
'00 Audi TT
'99 996 (Wife's ride)
'86 951 LS1 (C-2)
'77 911 3.2 (C-1) Gone but not forgotten.
3.2 Conversion and 915 Rebuild Home Page
The 958 Conversion
958 Track Video
PCA National Registry of Instructors
Marc
_____________________
'00 Audi TT
'99 996 (Wife's ride)
'86 951 LS1 (C-2)
'77 911 3.2 (C-1) Gone but not forgotten.
3.2 Conversion and 915 Rebuild Home Page
The 958 Conversion
958 Track Video
PCA National Registry of Instructors
05-14-2011, 11:40 PM
#71
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