S4 / GT brake confusion - more pics.
10-19-2007, 01:36 PM
#1
Burning Brakes
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S4 / GT brake confusion - SOLVED
Pic shows S4 ('88) and GT ('90) brake calliper that I thought would be interchangeble? Why has the GT got flats milled onto the bottom? Also, S4 large piston is 4mm larger than GT. Thoughts?
Last edited by bfellows; 10-27-2007 at 01:32 PM. Reason: solved
10-19-2007, 01:50 PM
#4
Rennlist Member
That GT caliper must be off of a different car...........the piston and calipers of the S4 and GT are same.
It was with the intro of thr GTS that the rotors and calipers were changed and only on the front.
It was with the intro of thr GTS that the rotors and calipers were changed and only on the front.
10-19-2007, 02:09 PM
#5
Drifting
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The piston sizes changed some in '89, and also again later. I don't know why, you would think larger pistons are better.
The search for correct pad dampers for S4 and later reveals a few different ones.
The search for correct pad dampers for S4 and later reveals a few different ones.
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10-19-2007, 05:11 PM
#9
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Brent............the WSM states the piston sizes pages 46-011 and 46-06 and the front calipers are listed as 44mm and 36mm except the '86 model where they're 42/36mm.
The GTS calipers are physically larger as are the rotors but the pistons remain 44/36mm. I've found no reference to caliper changes in the WSM for GT's but perhaps they're in the spec books...........I'll look there next.
The GTS calipers are physically larger as are the rotors but the pistons remain 44/36mm. I've found no reference to caliper changes in the WSM for GT's but perhaps they're in the spec books...........I'll look there next.
10-19-2007, 05:44 PM
#10
Burning Brakes
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Malcolm, thanks for all your help! I'm hoping this is just a case of mistaken identity so to speak, could be a strange anomaly? I've contacted the vendor and hopefully this will be an easy one to resolve.
10-19-2007, 05:58 PM
#11
Rennlist Member
No worries Bert............I've thought about this much trying to justify the $$$ to upgrade to the GTS brakes. The major difference between the S4 and GTS brakes are the front rotor size, the size of the caliper and the swept brake pad area. The rears are exactly the same.
The front rotors are 322mm GTS and 304mm S4...........the swept brake pad area is 75.5 sq. cm GTS and 65.5 sq. cm. S4.
I researched the Service Info Tech books for the S4, GT and GTS. Again, I can find no change to the brakes between the S4 and GT only with the intro of the GTS.
The front rotors are 322mm GTS and 304mm S4...........the swept brake pad area is 75.5 sq. cm GTS and 65.5 sq. cm. S4.
I researched the Service Info Tech books for the S4, GT and GTS. Again, I can find no change to the brakes between the S4 and GT only with the intro of the GTS.
10-20-2007, 06:42 PM
#14
Nordschleife Master
They are the same, except one caliper is meant to run in the trailing position while one is meant to run in the leading. To use a Big Red in place of a Big Black on say a 928 or 944, you simply need to reverse the position of the fittings.
10-22-2007, 02:54 PM
#15
Burning Brakes
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Sorry for the bump, but i'm still none the wiser on this one. Response on the 944 board seems to confirm that only 44mm pistons were used. Anyone else have a theory before i box it back up for a trip across the atlantic!