Early Dual Calipers/Master Cylinder

Oddjob

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Hi Guys,

I'm in need of some M/C advice...

I'm trying to revive a 73 TX650 that came equipped with dual calipers and a 22mm M/C. The calipers and M/C will most likely need to be replaced. I have read various threads that suggest that the 16mm stock single caliper M/C "might" be a better match for the dual caliper setup. I understand the reasoning behind the smaller bore generating higher line pressures etc., however I am concerned that I might not have enough lever travel with the smaller 16mm M/C to move all 4 caliper pistons. I haven't come across any threads that definitively state that they are running the smaller 16mm M/C on an early dual caliper brake system.

Has anyone run the smaller 16mm M/C on a dual caliper brake system?

Conversely,

Can someone with a 22mm M/C dual brake setup please provide a rough estimate of how much lever travel is required (excluding the free-play) to actuate the brakes, and how much clearance is left to the grip. My thinking is that based on the M/C's respective bore areas, I should be able to calculate the travel required for a 16mm M/C.

Thanks in advance
 
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I suppose you could approach this mathematically.

Force multiplication =
(Sum of the face areas of all caliper pistons) / (face area of master cylinder)

You can simplify by leaving out Pi, and just use the square of the diameters.

Force multiplication = (Sum of squares of caliper pistons) / (square of master cylinder)

Find the current force multiplication factor, then find what master cylinder diameter will get closest to that with your new caliper layout. The lever pull distance should remain the same.

If you alter the ratio (force multiplication factor), then the lever pull distance would change by the ratio of the ratios.

Ex: If only the master cylinder is changed, say from 22mm to 16mm, then the ratio change would be (22 squared) / (16 squared), or (484 / 256) = 1.89. Almost a doubling of the original lever pull...
 
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Hi TwoMany... I got to the 1.89 as you did... what I don't know is how much lever travel (excluding free play) there is on a 22mm M/C, and how much clearance there is to the grip to accompany the 1.89 X (what ever the 22mm travel is)...

:cheers:
 
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