Reply interspersed below...hope this helps rather than hinders;)
Brian
>Chris
>
>What it sounds like you are saying is that with all else being equal, the 3/4
>would require a longer stroke than the 7/8 to apply the same pressure.
Not quite right. The 3/4" requires a longer stroke to move the equivalent
amount of fluid to get the same caliper piston movement. Hence a longer
pedal. But it has greater leverage over the piston, so you get a lighter
pedal push to get the same braking effect. The rule is smaller MC, longer
pedal movement and lower pedal pressure. Larger MC, shorter pedal movement
and higher pedal pressure.
Is this
>is true, does anyone know the bore on the dual line master cylinders?
3/4" inch for stock disc brakes.
Would
>there be any reason to switch to the dual line other then the dual lines?
Dual lines are safer. They give poorer feel than single line. They are far
more complicated internally. They're a true pain to rebuild, to the point
where I refuse to use rebuilt stock dual master cylinders - Girling or
otherwise. They're very expensive (that's why I've used Datsun to replace
the dual MC in my race cars). But they are safer!
Does
>anyone know the reason the original switch was made from 7/8 to 3/4?
The original single MC had to work all the various drum brake slave
cylinders, front and back, and so had to move more fluid. That's the basic
reason for a larger MC size - the amount of fluid that has to be moved based
on the ratio of MC area VS sum of all slave cylinder areas and the distance
that all the slave cylinders have to move in operation. Then, you calculate
the pressures required in the various slave cylinders to do the work that
you need done, and you then get the pedal ratio and force, and see if it all
works out.
Was it
>because disks required less pressure than the drums to provide the same
>stopping power?, Or did it have something to do with the bore size difference
>between the calipers and the old wheel cylinders?
>
>Larry
>
>
Cheers, Brian Evans (who thought about this ALOT when redesigning the
braking system for his race Mini and Midget)
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