ShopTalk Forums | Aircooled VW Tech & Restoration Help

I've been reading, and reading and again reading, and yet I can not get to a conclusion. I installed 924S/944 disk brakes front and rear. As I have been documenting, I decided to plumb the brake lines in diagonal. Yet I think this is not a good solution for my car. Everywhere I can find info on front engine/front drive cars (to which the diagonal brakes are recommended) and on front engine/rear drive cars (to which front and rear circuits are recommended). Nothing on rear engine/rear drive cars. I tend to think it would be better to have separate front and rear circuits arrangement.
One more thing that bothers me: these Porsche brakes have larger diameter pistons on the front and smaller diameter pistons in the back. But these were designed for a front engine/rear drive car. Of course, they are far better than the old drums that I had, but could this be a problem? Maybe the light front end of the beetle leads to the front wheels to lock (according to Pascal's law, there will be a higher force on the front pistons, with the larger diameter, than on the rear pistons).
The last thing that I want to understand: how the brake master cylinder works: which circuit is pressurized first and which last? Maybe the connection of the front/rear to the circuits on the pump one way or the other can overcome the problems mentioned before.
Which configuration should I use (diagonal or front and rear)? and in case front and rear arrangement, to which circuits on the pump should each be connected?

Don't do this diagonal setup you're referring to. Very bad idea, especially if your car has an issue. I think what you mean is something like LF-RR on one circuit and RF-LR on the other?

I have 924T brakes on my '73 and they're great. I used a CNC drop-down pedal cluster with a balance bar, but understandably a lot of people won't do something this extensive. A lot of people use a limiting valve to the rear circuit, but I didn't like the idea of this as you're just limiting the amount of pressure going to the rears and I was planning on doing a hydraulic clutch anyway. A balance bar shifts everything to the front or rear MCs. You 'can' use the stock MC or a 944 one, a lot people do.

The idea that the fronts need more pressure than the rears is true for most cars...most cars not including a rear-engined VW. I must have adjusted my balance bar at least 10 times until I found the right setting (where the fronts wouldn't lock up anymore). The weight does shift from front to rear in a hard stop, but a lot of weight on a bug is already in the rear and just shifts then to the back seat area. I started with an 80% front, 20% rear setting but ultimately wound up with something near 50-50. A lot of other bugs have similar settings. Even so you still would not want to do a diagonal layout.

Another setup also in the tight footwell area:

http://www.germanlook.net/forums/showthread.php?t=10369

Thank you for your answer. I will change back to front/rear arrangement. I am now using beetle master cylinder, because the porsche unit failed. It has a longer stroke, but it feels softer, and the brakes react as they should.
Where should I connect the circuits to the pump? I have read that the front circuit should be connected at the mounting flange end (near the "firewall") and the rear circuit should go to the other end (to the front of the car). Is this correct? Does it make any difference?

Thank you one more time! This is the way I will connect the pipes.