The didn't know about the clutch wear tool but the thinner gasket won't make the slave push too hard against the release fork.

Self adjusting slave cyl like these have a deep bore with a light spring pushing against the piston to keep it extended. The spring is light enough to keep the slack out of the system ( release bearing in constant contact with the pressure plate fingers ) and allow for the fingers / release fork to move towards the cyl as the disc wears. The difference in new to worn clutch disc release fork height is much more than the difference between the home made gasket and factory shim.

If the flywheel was machined / slightly different clutch used, the measuring tool will be invalid.

Think of this as a disc brake caliper against new pads / worn rotors and new pads against new rotors. There is enough travel in the calipers to take up the difference in rotor thickness.

So you think there is enough space within the slave piston with the spring behind it to take up the discrepancy in body position and lack of a gasket? There could be - I'd have to check on that. But I'm not going to do that! My slave cylinder is fitted and bled and it ain't coming off for toffee!

I guess I'll alter my advice to say make sure the piston in the slave cylinder isn't all the way in the housing when you fit it with a modified gasket / shim / spacer. Distance is important.

__________________
1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!