why upgrade master cylinders

[moparrr07]

from what i have seen the stock cast master cylinder has a bore of 1 inch and all of the 80s aluminum ones everyone upgrades to has the 1 1/8 bore

now from what i know about hydrolics, the smaller the master cylinder is, the easier it is to push and more pressure it exerts, but it take a longer stroke to push it,

now i can do a hard stop without pushing my pedal down more than a inch,

why would i want to go to the bigger bore master, besides weight savings and it might take heat a little better? manual brakes arnt bad but i wouldnt want to have to push much harder than i already do

am i missing something here?

[BBLM23]

weight.

[mopowers]

now from what i know about hydrolics, the smaller the master cylinder is, the easier it is to push and more pressure it exerts, but it take a longer stroke to push it,

I'm curious how a smaller diameter master cylinder bore would cause more pressure in the brake line.  It seems to me if you exerted the same amount of pressure on a small and larger diameter master at the same time.  The small one would travel further than the larger one.  But the pressure in the line going to the brake would be equal.  Is this wrong?  Someone fill me in.

[67notchback]

just because you put the smaller bore master cylinder doesnt mean more pressure. it just makes for less fluid capacity. its not as if your going to squeeze the same amouth of fluid into the system and raise the hydrolic pressure. the smaller has a longer stroke so your going to have more pedal higher but the difference isnt noticable enough to make it a huge deal. the extral weight taken off always helps 

[73swinger]

Actually, a larger bore cylinder will ALWAYs make more PSI than a small one with same effort applied but the smaller one will move faster

[baumtruck]

pressure=force/surface area.  Thus the smaller bore would move a lower volume of fluid at a higher pressure with the same force applied.

[bOb shingler]

the real reason to change over is the iron are crap.

[farmington]

Plus the fact that in 10 years will you be able to find a iron replacement when yours goes bad?  Probably not.

[moparrr07]

chances are i will find one because they have remans available 35 years after the made the originals

mines a reman and cost $17 and i LOVE it, extremely easy to push, tons of braking pressure, i am just wondering if upgrading to an aluminum one will make it worse, then it wouldn't be worth the 2 lbs in weight savings

its just $17 for a higher pressure, or $80 plus an adapter for less pressure and harder to push, its not like pedel travel is a problem

[JD]

They have two different bore sizes.  I assume for power/non power applications.

Link to Mancini Racing's site
http://chucker54.stores.yahoo.net/mascyl.html

[375InStroke]

The input force is multiplied by the ratio of output area divided by input area.  If there is 10 square inches of piston area on the brake cylinders and calipers, and 1 square inch on the master cylinder, and you have 10 lbs. of force on the master, then you have 10 square inches divided by 1 square inch, giving you 10.  Then you multiply that 10 by the 10 lbs. of input force, and that gives you 100 lbs. of force.  The total movement of the brake pistons would be 1/10 the distance that the master cylinder moved, though.  If the master was larger, you would have a lower ratio, and less force multiplication as a result.  I think that the power masters are larger that the manual masters.  Aluminum would transfer heat more effectively to the fluid, which I'm sure is not good, and the weight savings is about the same as cutting out that Big Gulp before getting into the drivers seat.  I'd stick with the stock master.

[nd2stopfastr]

the master has a larger bore with non power for 73-up. also, if adding a heavier motor, a lighter m/c can help with weight distribution    aluminium is also not affected by DOT3 fluid whereas cast iron is. plus they were used well into the 80's as OEM pieces.

[loiq]

chances are i will find one because they have remans available 35 years after the made the originals

mines a reman and cost $17 and i LOVE it, extremely easy to push, tons of braking pressure, i am just wondering if upgrading to an aluminum one will make it worse, then it wouldn't be worth the 2 lbs in weight savings

its just $17 for a higher pressure, or $80 plus an adapter for less pressure and harder to push, its not like pedel travel is a problem

Sp you've driven them both and tested the pressure in both? Do you have any pressure numbers to share?

[75Dart440]

I have the aluminum MP master cylinder P5249271 on a stock-body Dart Sport with 440/auto and stops very well.  This master is for > 2800lb car weight.