Re: [Amc-list] rear wheel lock up problem still

["Swygert, Francis G MSgt 436 CES/CECM" <Francis.Swygert3@xxxxxxxxxxxx>]

Right. Pedal pressure is the inverse of fluid pressure. 
Larger bore master cylinder = lower fluid pressure, higher pedal
pressure, the driver is doing more work. 
Smaller bore master cylinder = higher fluid pressure, lower pedal
pressure, fluid pressure is doing a bit more. 

You don't get something for nothing! I've never seen enough difference
in bores across the board to be unsafe, not in 50s-70s American cars
anyway. Smallest I've seen is a 7/8", largest 1-1/4" A change form one
extreme to the other might cause a problem, but that's why I recommended
1/16" increments. Everything has to be considered and balanced for an
effective and safe braking system. 

I agree as far as Dave's problem goes -- a change in master cylinder
won't help. That would only help if both front and rear were locking up.
I started to answer Dave in my first brake post today, but it snow
balled into an overall brake post! 

---------------
Date: Tuesday, February 13, 2007 12:03 PM
From: Tom Jennings <tomj@xxxxxxx>

On master cylinder bore size: this has no effect on front:rear
balance, only pedal pressure and travel.

If the master cylinder bore is larger than factory-design,
pedal pressure will be higher and stroke will be shorter.
I have this setup in my 63 Classic. It makes for HEAVY pedal
but is otherwise totally fine and safe.

If the master cylinder bore is smaller than factory design,
pedal pressure will be lower and pedal travel will be longer.
If the pedal travel is too much then there won't be enough
fluid in each stroke for safe braking and that could be fatal.
I doubt you could really achieve that bad state though with
mix'n'match brake parts that AMC used; I've never seen more
than 1/8" difference big to small masters and slaves.

In AMC dual piston masters, the Front and Rear bores are
always the same -- hence the master to front and master to rear
ratios will always be the same and balance front to rear will
not change.


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