924Board.org

[safe]

Trying on some calipers...
Just need to fabricate the adapters in metal instead of 3d printed plastic....


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/Magnus, Stockholm Sweden
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Porsche 924 -79 NA, EFI and Turbo.
Porsche 931 -79
Porsche 911 -77, 3.2 Targa
Porsche 911 -69, 3.6, Coupe

[safe]

Drums turned down to hubs, left first attempt, right the second and final.


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/Magnus, Stockholm Sweden
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Porsche 924 -79 NA, EFI and Turbo.
Porsche 931 -79
Porsche 911 -77, 3.2 Targa
Porsche 911 -69, 3.6, Coupe

[Beartooth]

That looks like a pretty nice setup, safe! You've got me thinking about some possibilities on mine, and I've got some ideas... I don't think I'm going to find Peugeot parts, but some late 80s and early 90s Audis (looks like the 80 is the best bet) have the same 4x108 bolt pattern, a high offset rear rotor, and the same diameter front rotor as the 24 solid disk. Two-piston calipers might even be an option out of the S4 or V8...

Since you mentioned the Ford parts, I looked into that, and it might just be an option - maybe even for the hydraulics. Not many Audis in the wrecking yards around here, so it might be worth getting a set of rotors and calipers from a Focus and/or Contour (US version of the Mondeo) to play around with.

One thing I'm wondering is if there's any rough guideline to follow that'll keep the front-rear brake bias where it should be. I notice the Audis I mention have 54mm front pistons, and 38mm rears. The Fords are 54/34 for the Focus, and 60/36 for the Contour. I suspect those would have more front bias to account for the weight, so I wonder if mixing and matching to get 54mm front pistons and 36mm rears would be a good idea. I don't know if they have a diagonal split like the 24, or how that plays in, but it seems the master cylinder is pretty similar (on the Focus anyway - 23mm bore, no step).

Anyway, I think I have a good starting point if I go down this road. I might try and dig up a pair of drums and rotors to machine and start mocking and fabbing around - that way if I get in a bind I can just put the old stuff back on until I figure it out.
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1980 931 diamond in the rough

[safe]

[Cedric]

[safe]

I've just done a "final" fitment of the rear calipers with the finished adapters. Working on the hand brake cable set up, I need some form of holder/adjuster.
_________________
/Magnus, Stockholm Sweden
=======================
Porsche 924 -79 NA, EFI and Turbo.
Porsche 931 -79
Porsche 911 -77, 3.2 Targa
Porsche 911 -69, 3.6, Coupe

[safe]

Yes, regarding brake lines etc, I rerouted them to be front/rear and changed the master cylinder from the 924 NA to the 931 23 mm with equal sized front/rear. The 931 master was "reasonably priced" at about $200-250.
I first looked at a early 944 master (19,05 / 23,81mm) and that was $900!!!
Then a later 944 (23,81 / 20,64mm) at $300.

After that $200 felt like a steal
_________________
/Magnus, Stockholm Sweden
=======================
Porsche 924 -79 NA, EFI and Turbo.
Porsche 931 -79
Porsche 911 -77, 3.2 Targa
Porsche 911 -69, 3.6, Coupe

[Beartooth]

Yup, that master cylinder is pricey for what it is, but it could be worse. Of course I had to replace most of my brake and clutch hydros, although the clutch slave cylinder still works, and I was able to rebuild the calipers.

Anyway, I was surprised too that Audis had four-lug wheels so far along. Mercedes has been five-lug forever, and most American stuff outside of compacts are too.The B3 and B4 Audi 80s are the ones you'd most want to look for, but I'd look under any mid-80s to mid-90s with four lugs. Unfortunately, those were very thin years for Audi in the US - I can't even find one on Copart (which is corrently showing three 924s...) If you find a wrecked 20V, you've got the ingredients to turn a basic 24 into a wolf in sheep's clothing...

Thanks for the number on the 931 (I presume that's the five-lug brake setup). On the brake bias and proportioning discussion, my thought would be to avoid any modifications you can - I'd want a setup that only needs to be hooked up to the existing lines. It looks like using the Focus calipers (54mm) in the front and Contour calipers in the rear (36mm) would give me 69.3F/30.7R distribution. I'm guessing that's still front-biased to some degree on a 24; you could shift that to 67/33 by going to a 38mm rear caliper, but I don't suppose it's worth the risks on a street car.

Ultimately, I'm hoping to find a set of readily-available parts that'll allow you to match or at least get close to the M471 brakes for cheaper and without having to find a donor car or pay shipping for a pile of parts. If you hit on the right setup, it would be a no-brainer except for the machine work to turn the rotors/drums into hubs. On the front at least, it looks like once you get the rotor machined to a hub (and I bet you could machine the face to make a centering ring for the rotors), the rest could be all bolt-on stuff (using Passat calipers). Too bad the rears are more complex, since that's where you get most of the benefit outside of sheer fade-resistance. Anyway, since I'm going to be rebuilding my engine this spring anyway, maybe I will just start cutting.
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1980 931 diamond in the rough

[Cedric]

[Raize]

You could also just mess around with your pad compounds to balance the braking force if you need to.