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  #1  
Old March 24th 2024, 17:36
Tomas Tomas is offline
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Brakes advise

I'm converting my 1303 to electric using a Tesla Small driveunit and therefore have to upgrade my brakes. Have got Porsche 944na spindles in front and rear arms from the same 944na. Can I use the rear 4-pot calipers from a 2003 Boxster at the front of my 1303 or is there better options? I also got the rear 944 brakes
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  #2  
Old March 25th 2024, 00:02
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You have to look at the piston sizes, and do some calculations to figure out if you can use the 2003 Boxster rears upfront.

For my German Look, I'm running Boxster calipers on all four corners, fronts on the front. Rear calipers on the rear. The fronts use 944 hubs modified to my beetle spindles, and 1976 911 rotors. This mates up perfectly with the front calipers (with custom caliper mounts). On the rear I'm using 944 bearing retainers (which have the caliper mount built in), 944 turbo rotors, and the Boxster calipers. No mounts or adapters needed.

The piston sizes come into play with the Rally Bug. Currently it runs the 2-piston Ghia calipers (solid rotors) on all four corners. I have a set of 951 rear calipers coming off an Audi that I thought would make a great front brake update for the Rally Bug. BUT the combined piston area of the four piston Porsche rear caliper is smaller than the combined piston area of a 2-piston Ghia caliper. Thus, the car would end up rear biased. Can't use em.

So, for your rear boxster calipers on the front question, you need to do some piston math and compare them with your rear calipers. I use https://brakepower.com/piston-area-calculator.htm

-Dave
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  #3  
Old March 25th 2024, 00:12
Tomas Tomas is offline
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Thank you owdlvr for your reply! Yes I might source front calipers also.
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  #4  
Old March 25th 2024, 11:42
Tomas Tomas is offline
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Still find it difficult to get the right parts, can someone please help me out what the options are? Boxster S calipers seems easier to get hold of. But which discs should I use if I go Boxster or Boxster S calipers? Using 944 spindles and 944 rear arms
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  #5  
Old March 26th 2024, 01:09
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Boxster vs Boxster S rotors:

Non'S':
F Disc 298mm, Pistons in Calipers 2x40,2x36 mm , pad area 216 cm^2
R Disc 292mm, Pistons in Calipers 2x30,2x28 mm , pad area 196 cm^2
Thickness (new): 24mm front and 20mm rear

"S":
F Disc 319mm, Pistons in Calipers 2x40,2x36 mm, pad area 254 cm^2
R Disc 299mm, Pistons in Calipers 2x30,2x28 mm, pad area 196 cm^2
Thickness (new): 28mm front and 24mm rear

S rotors are thicker AND larger diameter.
S pads are larger
S calipers bolt in place of non S ones

Boxster S brakes are identical to Porsche 996 brakes.

But I don't know a front rotor that's going to work off hand for the S. For the regular boxster, it's easy. For the S I'd have to start going through them part for part.

-Dave
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  #6  
Old March 26th 2024, 08:48
Tomas Tomas is offline
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Which mastercylinder do you use with the Boxster calipers?
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  #7  
Old March 27th 2024, 00:47
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Presuming factory pedal setup. Empi Big-Bore master cylinder for disc brakes.

Yes. Seriously.

Pedal feel is spot on.
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  #8  
Old March 29th 2024, 09:13
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Quote:
Originally Posted by Tomas View Post
I'm converting my 1303 to electric using a Tesla Small driveunit and therefore have to upgrade my brakes. Have got Porsche 944na spindles in front and rear arms from the same 944na. Can I use the rear 4-pot calipers from a 2003 Boxster at the front of my 1303 or is there better options? I also got the rear 944 brakes
I hope you have also planned space for the Tesla on-board tools.

https://www.instagram.com/p/CwOqcvYIUxY/
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  #9  
Old March 29th 2024, 22:33
Tomas Tomas is offline
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Quote:
Originally Posted by 412STi View Post
I hope you have also planned space for the Tesla on-board tools.

https://www.instagram.com/p/CwOqcvYIUxY/
Well I'm switching controlboard in the motor so there's not much Tesla electronic left. Batteries are from BMW i3.
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  #10  
Old April 10th 2024, 23:40
flat flat is offline
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I'm running BoxsterS on my 1302, stock master cylinder. I've done tons of Boxster setups on beetles too, using stock master (19mm) or the 20.6mm mentioned above. The 19mm engages about halfway down, but requires less pedal effort than the 20.6mm. You can also use a mk2 golf mc with adapter.

Boxster non S is preferred IMO, less unsprung weight. And for a bug you don't need the increased thermal mass/capacity of the S setup.

Here is the rotor and caliper info, all non-S model. The non-S calipers come in black from factory.

Calipers front:
Boxster 2.5/2.7 97-08
Cayman 2.7 07-08
986 351 421 03 left
986 351 422 03 right

Calipers rear
Boxster 2.5/2.7 97-16
Cayman 2.7 07-14
986 352 423 01 left
986 352 424 01 right

Rotor front (298*24mm)
Boxster 2.7 05-08
Cayman 2.7 07-08
987 351 401 01 left
987 351 402 01 right

Rotor rear (299*20mm)
Boxster 2.7 05-16
Cayman 2.7 07-16
987 352 401 01
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