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Anyone have any experience of what size of handlebar MC to use on the earlier 38mm brake calipers?
Thanks. Charles

Here is a handy m/cyl to caliper ratio chart that may help.
http://www.vintagebrake.com/mastercylinder.htm

I have never determined for sure if I have the 38 or the 40 slave, but I have a 13 mm Master that works fine. I suspect it would work fine for either as there were folks posting that they had even gone to duel disks with the 13 and not run out of lever.

All 40 mm caliers I have seen have "40" stamped into them. FWIW

Native /5 wrote:All 40 mm caliers I have seen have "40" stamped into them. FWIW

The local mechanic (Roger Albert) here tells me that the 40 was stamped on them only in the year they changed and that having the stamp tells you it is a 40, not having the stamp doesn't tell you much. Heresay only. I have not seen that written down anywhere, but Roger is pretty good.

Having learned that there was two sizes out there - I still have not even looked for the stamp. Its a memory thing - now where are those keys.....

Use the smallest you can find - a 12 mm gives a good solid feel and a good bit power, a 11 mm is better if you can find one. Guzzis used them with twin 48 mm Brembos with no problems.

Remember that the undertank MC had a lever with about a 2 1/2 to 1 advantage, so even with a 11 mm MC you will still have less pull at the lever.

Had an 11mm on a race bike, it worked very well!! but yes they are hard to find,mine was a magura. Find some ferodo platinum pads....these are the best!!!
http://www.vintagebrake.com/pads.htm