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barryh wrote: ↑Sun Jan 01, 2023 2:49 pm it makes sense in that scenario to move to a 38 mm Brembo what ever else is done.

Thanks for the information. Because your reply didn't include a take on the number of discs, I take it as single disc would still be adequate for two up driving given that the driving habits are not sporty, and that the speed limits are respected.

The original brakes are one more reason to respect an agreement with my wife in that she will ride with me without a sissy bar on a condition that I'll keep the speed under 60 km/h.

Yes it was all referring to a single disc and an improved single disc setup would be a significant improvement.

barryh wrote: ↑Sun Jan 01, 2023 6:40 pm Yes it was all referring to a single disc and an improved single disc setup would be a significant improvement.

I think your figures must relate to a twin disc set up e.g.

Single disc 12mm x 38mm

area of master = 113.1 sq/mm
area of slave (caliper) = 1134.1 sq/mm

Ratio approx 10

Twin disc 12mm x (38mm x 2)

area of master = 113.1 sq/mm
area of each caliper = 1134 .1 - 2 calipers = 2268.2

Ratio approx 20

Of course, the brake effectiveness also has to take into account the leverage ratio of the lever (which can be regarded as a bell crank and, I suppose, in this application might be regarded as almost a constant) and the effect of lever movement on the ability of the human hand to apply pressure. Increasing the master/slave relationship results in greater movement of the lever which, if it becomes too great, effects the ability of the riders hand to apply pressure.

Rob