Increasing clutch m/cyl size

[wazrs257]

I've been gathering a few bits together for my GSXR7/11 project, and wanted to replace the standard 1100 clutch master-cylinder (with integral reservoir) for a remote reservoir type to match the brake side. I remembered reading somewhere that a YZF750 one would fit the bill, so purchased one from ebay. It arrived today, but it is 5/8" (15.875mm) compared to the GSXR11s 14mm. It's been alot of years since I studied hydraulics at college, but I seem to remember that increasing the master-cylinder piston size will displace more fluid for a given amount of lever travel and therefore the clutch should 'clear' ok, but at the expense of requiring more force for the same amount of travel.

Do I remember correctly, or do I need to go back to skool?

[porter_jamie]

you are correct.

smaller master cylinder gives less effort at lever, but less travel at the slave cylinder for the same lever movement

(or more travel at the lever for the same travel at the slave cylinder, iyswim)

for info, 15.875 and 19.05 clutch m/cyl is fairly universal in most current cars, they use the same hydraulic ratios on all of the different variants and tune the overcentre spring in the pedal box to tune the pedal efforts.

lots of people who should know don't know why it's 19.05 and not 19.0, which suprises me.

[wazrs257]

Thanks, at least something sunk in!

lots of people who should know don't know why it's 19.05 and not 19.0, which suprises me.

Am assuming something to do with them being imperial sizes?

[porter_jamie]

exactly so. i was actually talking to someone who works for a company that make literally millions of them a year recently, they didn't really know. i like to think that having to make something to imperial sizes actually winds them up a bit, being all european and efficient, if you know what i mean. i expect the michelin hate having to make tyres in metric widths but imperial diameters, given they probably think they invented metric.