[Unber-j]

whats the performance difference between the 28mm and 30mm STM Clutch Slave Cylinder. I'm looking to change my stock one (2001 748s) its leaking pretty bad.

 

[DukeDesmo]

The 30mm will require less force to pull than the 28 but will not separate the plates as much as it will move less distance - the trade-off for less force is more travel.

Either way you will probably need your lever on the largest span setting to be able to find neutral.

 

[Unber-j]

So the 28mm will engage the plates better...ok, Do you think I'll have to move my lever out as far for the 28??

 

[DukeDesmo]

I have an Evoluzione slave cyl which, I believe is 28.5mm and it really needs the 4-way lever setting on #1 (largest span) otherwise neutral can be tricky to find, especially if the clutch pack is slightly thicker.

Although I have since removed 2 springs from the clutch and with the right clutch pack thickness could probably get away with #2 setting but I like #1 as it suits my hand size.

If you go too large with the bore of the slave cyl you can get clutch engagement/disengagement problems which also depends on which master cylinder ratio you have.

Shazzam posted a useful chart showing the effects of different cylinder/ratios that may be of help;

 

[moto]

I had the STM Clutch Slave Cylinder: 30mm on our 1098 project bike.

We replaced it with the OBERON Clutch Slave Cylinder 29mm . It was easier to find neutral with the Oberon slave. Clutch pull was exactly the same.

 

[sunstar557]

Leaking STM slave cylinder

FWIW, after four years of use, approx., 15,000 miles, my STM slave cylinder started to leak. I'm not sure whether to judge this a reasonable expectation of life... maybe. I've put on an Oberon slave cylinder now.

 

[Agro]

I've had both the STM and the Oberon and neutral is difficult to find, compared to stock for me. I dont sweat it a lot as it's a track bike, but still annoying. Trade offs I guess.