944T brembo brakes on vw - which master cylinder size?

[evilC]

The 19/19mm dual master cylinder as standard in the bug should be up to the job. You will find that the minimal clearance between pad and disc of about 0.014" will give a result for the amount of pedal movement. There is a lot of nonsense/B******t talked about 'upgrading' m/cs, the only upgrade I know of for an m/c is the quality of construction not the size.
The 20.6mm m/c will give the following:
17 1/2% less pedal travel than a standard bug m/c
17 1/2% greater pedal effort than a bug m/c
(all due to its 17 1/2% bigger piston area)
You can easily calculate the expected pedal travel knowing the clearance and the total piston size in the calipers and m/c. Allow 5mm travel for a properly set up clearance on the piston rod. The calc will only give you the amount of movement until the pad touches the disc thereafter it is subject to whatever pads you use and the temperature of that pad (amount of squish). Very hot pads near to their working limit can compress dramatically.

Clive