Anyone have one laying around that can mic the thickness of the top hat that sits between the hub and the wheel?

 

In the MIL's garage- if you can wait till tonight/tomorrow, if no one chimes in first, I'll get a measurement for you.

 

Thanks Rob, also the rotor pad sweep depth if you can. Would be a big help.

 

Here's a start for comparison, and as accurate as I can get with the rotors on the car.

I measure the pad swept area depth at 60.0 mm = 2.372" starting approx 1.5mm from the outer edge. Total available rotor swept depth is 64.5mm = 2.539".

I measure the hat thickness at the threaded holes for pushing the rotor off at 6.0 mm = 0.237" , but I'm getting a variation from hole to hole of about 0.1mm = a gnats nut ... a bit hard to get it more accurate than that without the rotor being off the car.

 

I have a couple of new front GTS rotors in stock. The thickness of the top hat is measured to 5,95mm, nominal value is 6,0mm so this is within tolerances. The rotor pad sweep depth is 64mm. The brake pad width (Textar) is 59,5mm.

Åke

 

Thank you Dave and Ake. To confirm the total height, are they 77.0 or 77.3mm tall. I've seen tech drawings with a couple different dims......At any rate, this is good news as I need to use a taller rotor to get a thicker/stronger adapter done.

 

I measured one of the GTS rotors and the total height is 77,06mm. The nominal height is 77,0mm, this is within tolerances.

Åke

 

GTS rotor hat thickness is between 6.2 and 6.3 mm, or .2495". But these are pre-loved ZImmermans, not factory GTS rotors.



I think the swept height is about 55.5 mm. Somewhere here I have a set of new factory GTS brake pads, will try to get dimensions on them.

 

Thanks again guys, this is interesting as it looks like Porsche just increased the diameter of an M030 rotor to get the GTS rotor.

 

Here's a pic of the pad swept dimension measurement on my left genuine GTS rotor .. as already noted, full swept dimension is 64.5mm.

I've also measured the total rotor height from the OD of the hat and I get a little under 76mm on both sides.

 

Thanks also Dave. What are the GTS Big Blacks piston Sizes?

 

Big black pistons are 36 and 44 mm, same as S4 fronts.

 

Except early '87 USA, Canada and Saudi Arabia S4 which still used '86½ S3 calipers and thus got 36 and 42mm.

 

Thanks Erkka, amending my notes appropriately.

Found those GTS front and S4+ rear pads today.

Some pics:




Front GTS (Textar T4045 FF):










Rear S4+ (Textar T428 FF):

 

Ok keep posting these specs. I don't have a GTS Big Black caliper on hand although I have made adapters for them before. I acquired "Bigger Black" caliper last week that looks like those pads would fit. It has an Audi stamp on them with no other identifiers, 40 x 44 mm pistons, and looks like the annulus accepts a 350mm rotor.

If you have the big black GTS caliper handy, could you post the bolt-thru center to rotor center measurement? Thanks again, I'm just weighing my options on which one-off kit Ill build.