GL 1303S project from Romania

[Xellex]

I think that would only be true if the calipers were the same size front/rear, and if the 19mm would push enough fluid to succesfully move the big NA 944 front caliper pistons.
Your thinking makes perfect sense, but imho the total volume of the pistons inside the calipers at full braking (expanded the most / brakes locked) has to be equal or lower to the volume of the piston inside the MC when pedal is released. If it's bigger then there's a big problem.
So yes, the lowest volume MC piston is the best, but there's a lower limit, and there's also a higher limit, to the point where brake effort is too high, and pedal travel is extremely small.
The question is: does the 19mm MC fit somewhere above that lower limit? Ofcourse on the street/track you could get great results, and good braking because the bug is so light.
And the second question is: what does that do to the rear, lower volume calipers? Probably locking them too early.

That's just my late night thinking, and the only fluid dynamics classes I took were in college, so I could be very wrong.

Anyway I'll just do the extra plumbing and mount the MC the normal way.
Thank you for your response, I apreciate it.

[flat]

I've tried to stock 19mm dual circuit MC with 944NA brakes, and it doesn't work well. Not enough volume. You need the 944MC for the NA brakes. With aluminum brembo's, the stock 19mm works extremely well.

Lanner

[evilC]

The original standard m/c for the 944 was a 19/19 unit that was later changed to 23/19 and that is the one that most people refer to as the 944 m/c. Fluid volume is not really the issue with a fully working system with good lines and fresh fluid (well bled). The basics of hydraulic advantage is that the pedal effort is multiplied by the area of caliper pistons (2No.) / area of mc piston. The stand off of the pad from the disc is very small so as minimise pedal travel. The main effects on pedal travel are hose bulge and water/air in the system that then compresses.
On a bug with a larger caliper piston area at the front than on the rear the stepped m/c can be of some advantage as the desireable brake bias is unity i.e. the braking effort front and rear should be about the same. The larger m/c piston is around 45% larger in area than the smaller piston and therefore gives 2/3rds the fluid pressure than the rear line.

evilC

[Wally]

Yeah, that too

[flat]

I've just speaking from my experience. The 19mm stocker didn't feel right with the 944NA brakes, the pedal travel was too deep. Everything on the car was new/rebuilt, with fresh fluid in the system. It would brake, but you felt the need to pump the pedal to get the required volume. Swapped it over for a 23/19 MC and it was amazing. Tall pedal + great clamping = driver confidence. The 19mm MC worked, but the 23/19 worked MUCH better.

So, the question boils down to this: Has anyone used a 19mm stock MC on a 944 NA brake system with good success?

Lanner