QUOTE(turnaround89 @ Feb 27 2017, 01:29 PM)
What's the best way to size up a clutch master cylinder for the clutch slave cylinder?
Can you undersize a clutch MC for the slave cylinder?
Yes you can! It is a ratio and pressure thing.
So it can be a bit of a math trick. My slave is 3/4" bore, I am not sure of the travel. My master is also 3/4" bore not sure of the travel there. Best case scenario I am at a 1:1 relation ship.
Now for the fun, the clutch slave pushes the clutch fork, and it is a simple lever. The pedal is also a lever, so the trick is to get it so it feels good, while being at a ration that is soft enough to push.
Simplest thing I can relate this to that you might know is the 914-4 brake pedal and master cylinder. Stock -4 size is 17mm, it will stop the car perfectly, yet the pedal feels soft. So most people will upgrade to a 19mm master. It firms the pedal up, and some like that feeling, as do I. IT is a square of the size of the bore, the and the ratio of the two.
So it can get complicated, and a bit of math, with a few variables I don't know off the top of my head.
Here is a good overview of how it all works.