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Porsche boxster 4 piston brakes (NQSBBK) fitted on MK7 GTi.

spelk3

Ready to race!
Location
Mountain View, CA
Car(s)
‘17 BMW xDrive35i
Sorry to bring up and old thread...

I'm thinking about doing this caliper swap. Does anyone know how much more the Boxster calipers stick out toward the wheel spokes compared to non-PP calipers? I have 17x8 et45 wheels and I would like to know if I will need spacers.
 

spelk3

Ready to race!
Location
Mountain View, CA
Car(s)
‘17 BMW xDrive35i
Progressive piston setup, 36mm and 40mm, the ratios are very close to stock and perfect for the master cylinder.

Stock brakes Golf/GTI - Ate FN3 54 mm caliper : 2290 mm²

Boxster: 40 mm + 36 mm : 1257 mm² + 1018 mm² = 2275 mm²

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The front calipers on the mk7 GTI use 57mm pistons, so the area is 2552 mm².

The difference between the Boxster caliper and the GTI is 277 mm², about 10% smaller for the Boxster. Is that enough of a difference to cause any problems?
 

WhiteTDI

Passed Driver's Ed
Very nice!!! Yes, I forgot to mention that the crossover tube need to be switched from one caliper to the other.

May I suggest you get a black Porsche decal on those yellow brakes?!?

I love the look man, koodos, and yes I know they feel great!!! :)


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sorry to bump an old thread, but i'm in the process of doing the 996 calipers w/ B5S4 rotors. regarding the crossover tube, are you saying just interchange the tubes from the driver to passenger side, and vice versa? or crossover tube from the VW caliper to the Porsche caliper?

TX_TDI, can you elaborate on the custom crossover tubes you had made... got any more pics?
 
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DAS_STIG

Banned
Location
Chicago
sorry to bump an old thread, but i'm in the process of doing the 996 calipers w/ B5S4 rotors. regarding the crossover tube, are you saying just interchange the tubes from the driver to passenger side, and vice versa? or crossover tube from the VW caliper to the Porsche caliper?

TX_TDI, can you elaborate on the custom crossover tubes you had made... got any more pics?

I believe it's the driver side <-> passenger side, since you're moving which piston should "brake" first by switching the mounting position of the caliper.
 

Reggie Enchilada

Autocross Newbie
Location
nowhere
Car(s)
yes
You don't need to switch the crossover tubes. The left caliper goes on the driver's side of the car and the right caliper goes on the passenger side of the car. The crossover tube orientation doesn't change from donor car to your car.

The only difference between how they sit on the donor vs. your car is that they sit on the read side of the rotor on the donor car and on the front side of the rotor on your car. Effectively, it's like they are rotated 180 degrees around the hub.

Install them this way and hook up the crossover tubes the same way that they were on the donor car. The smaller piston will bite first, then the larger one as the brake pedal is pressed more.
 

DAS_STIG

Banned
Location
Chicago
You don't need to switch the crossover tubes. The left caliper goes on the driver's side of the car and the right caliper goes on the passenger side of the car. The crossover tube orientation doesn't change from donor car to your car.

The only difference between how they sit on the donor vs. your car is that they sit on the read side of the rotor on the donor car and on the front side of the rotor on your car. Effectively, it's like they are rotated 180 degrees around the hub.

Install them this way and hook up the crossover tubes the same way that they were on the donor car. The smaller piston will bite first, then the larger one as the brake pedal is pressed more.

So will the folks that did switch the position of the crossover have issues?
 

Reggie Enchilada

Autocross Newbie
Location
nowhere
Car(s)
yes
The 986 Boxster calipers have 36mm and 40mm pistons. The crossover tubes go on the side with the 36mm pistons. They come from the factory that way. There's even a notch in the end of the caliper that they sit in. Here's a picture of a 986 S caliper. It's a little bigger, but set up the same way. I've also included some quickly drawn diagrams of how the caliper should be oriented on a MK7 and how it is oriented on a 986 Boxster.
 

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Reggie Enchilada

Autocross Newbie
Location
nowhere
Car(s)
yes
You want the bleeders on the top, so given your drawing you would want to swap the crossover tubes.

The bleeders go on the ends with the 40mm pistons. The crossover tubes go on the ends with the 36mm pistons. It's made to fit that way and it's how they come from the factory.
 
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spelk3

Ready to race!
Location
Mountain View, CA
Car(s)
‘17 BMW xDrive35i
Shouldn't a power bleeder or manually bleeding them resolve that issue? I can definitely see that being a problem if you try to gravity bleed them though.

For the VW application you want the crossover tubes on the end of the caliper with the 40mm piston and the bleeders on the 36mm end. You really don’t want the bleeders on the bottom end of the caliper.
 
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