On earlier bugs they all had single circuit brakes with a 19mm master cylinder; then in 65 VW went to a 17mm cylinder.

What would be the benefit of changing to a smaller cylinder??? I think that earlier 911's had 17mm cylinders

Cheers

Shaun

Basic hydraulic maths. Smaller input piston and larger output piston means greater pressure on the output piston but more effort required on the input piston. Also, the larger the output then the less it travels in relation to the inputs movement.

A smaller bore master cylinder would produce a higher line pressure with reduced with pedal effort, all being equal, if you left the standard wheel cylinders it would require more pedal travel to get the brakes to work but would produce a greater braking force, i do not know if the models that had the 17MM master cylinder had a change of wheel cylinder size to allow for the reduction in master cylinder diameter, If your car has a 19mm master cylinder you might end up with excessive pedal travel.

Later models used 17mm on the rears but believe stayed at 19m on the front 40mm dual piston calipers.

I'm also pretty sure that my brand new ATE dual MC is 19m bore and not 17 and that all new MC's are this way.

Talking about a single circut master cylinder on the earlier cars.

Didn't know they change the singles bore size