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Master cyl size
Topic Started: Sep 7 2015, 03:47 PM (636 Views)
fredcc
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Dj3a new wheel cyl and shoes drums like new wheel cyl 1 inch front
and 3/4 rear what is the correct size master cyl. Thanks for any
help with this Fred
1965 DJ3 CONVERTIBLE In work
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SteveK
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Hey Fred, I'm no expert but in my research for my 62, all I've seen indicated for the Dj Master cylinder size is one inch. The wheel cylinders do seem to have two different set possibilities. Yours, and mine, are 1" and 3/4", but specs often shown say 13/16" rear cylinders and 1-1/8" fronts. Which is 'better' is a burning question I would love to see some conversation on from the group, and opinions and reasoning choosing either set would be great for consideration for all of us. Good Luck.
SteveK
62 Dispatcher
South Florida
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fredcc
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SteveK,Sep 7 2015
10:11 PM
Hey Fred,  I'm no expert but in my research for my 62, all I've seen indicated for the Dj Master cylinder size is one inch.  The wheel cylinders do seem to have two different set possibilities.  Yours, and mine,  are 1" and 3/4", but specs often shown say 13/16" rear cylinders and 1-1/8" fronts.  Which is 'better' is a burning question I would love to see some conversation on from the group, and opinions and reasoning choosing either set would be great for consideration for all of us.  Good Luck.

Steve, My thoughts on this would be if your running the small wheel cyl
you need a smaller master cy' to keep the pedal pressure down..
I remember when I was very young my father showing me a master cyl
with piston in a piston the outer one taking up the free play and the inner
applying the pressure. This may spark some comments. Fred
1965 DJ3 CONVERTIBLE In work
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SteveK
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Hey Fred, Thanks for sharing that experience. I had never heard of something like that. To take care of that "free play", I used a check valve on the front of the master cylinder. I say 'front', because I also modified my Brake Flow to straight out the front, with the Stop switch off the side of the Banjo fitting. The 10# check valve holds that minimal pressure against the return springs of the brakes taking out the lag response. 10# is not enough to apply the brakes or drag them (per Wildwood Brake Company). With the switch behind the check valve, initial pedal pressure application will ignite the 4-7# switch before exceeding the 10# pressure to help wake up tailgaiters without braking. I also removed two hard bends on the supply line allowing maximum flow with minimal resistance to push those brakes as hard as possible when needed. Before too much longer, I hope to put my project on the road and see how it all works, and hopefully never in an emergency situation.
SteveK
62 Dispatcher
South Florida
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oldtime
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Quote:
 
Dj3a new wheel cyl and shoes drums like new wheel cyl 1 inch front
and 3/4 rear what is the correct size master cyl.


Early DJ's all have 9" brakes but they are wider than the 9" CJ brakes which increases the effective area.
For that reason the DJ cylinder bores were increased.
DJ front wheel cylinders should be 1-1/8" and rear should be 13/16".
CJ's with 9" brakes have 1" front wheel cylinders with 3/4" rear wheel cylinders.

All 1942-1966 CJ and DJ master cylinders have a single bore @ 1" bore diameter.
(excepting post 1967-1/2 and later with split bore master cylinders)
Dual safety master cylinders were Federally mandated in mid year 1967
Currently building my final F-134 powered 3B .
Rock Crawler using factory parts from the Willys Motors era (1953-1963)

http://s4.zetaboards.com/CJ3B_Bulletin_Board/topic/30228766/1/#new
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fredcc
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Old time, Thanks for the info on the wheel cylinder size I will start
iooking for a set of cylinders. Thanks again Fred
1965 DJ3 CONVERTIBLE In work
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oldtime
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806042 = Right front cylinder @ 1-1/8"

806041 = Left front cylinder @ 1-1/8"

803641 = Both rear cylinder @ 13/16"

909583 = Master cylinder
Currently building my final F-134 powered 3B .
Rock Crawler using factory parts from the Willys Motors era (1953-1963)

http://s4.zetaboards.com/CJ3B_Bulletin_Board/topic/30228766/1/#new
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SteveK
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As seen with Fred's 65 and my 62, the factory seems to have varied later from the original early sizing to 1" and 3/4". I know mine is original, as I know it's history. Anybody else out there with 1" and 3/4" cylinders and with what year? Charles, I know you have a 56 and a 63. Have you compared the cylinder sizes yet?

FYI...I have a Willys spec sheet showing the smaller combo up to 11" brake systems, and that was on an early year spec sheet along with the Dj 9X2 brakes. Maybe the factory knows something? So, my question still stands...

Quote:
 
I'm no expert but in my research for my 62, all I've seen indicated for the Dj Master cylinder size is one inch. The wheel cylinders do seem to have two different set possibilities. Yours, and mine, are 1" and 3/4", but specs often shown say 13/16" rear cylinders and 1-1/8" fronts. Which is 'better' is a burning question I would love to see some conversation on from the group, and opinions and reasoning choosing either set would be great for consideration for all of us.


I'm thinking mathematically, the same size MC valve (1") and same 'foot pressure' at the MC with smaller cylinders, it should yield more 'pressure' available at the cylinders. Larger cylinders will yield more 'volume' but with 'less pressure'. I'm wondering if anybody has experimented with the sizing and what results you found? Thanks!
SteveK
62 Dispatcher
South Florida
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PapaC
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Quote:
 
SteveK:  Charles, I know you have a 56 and a 63. Have you compared the cylinder sizes yet?



Steve, my plate has been beyond full for the past month or so because of the sickness and passing of my dad and I haven't touched a jeep part in weeks. Also my daughter is having a another baby in less than two weeks and me and Debra are spending a lot of time with my mom (they were married for 63 years)



I will also say that oddly enough I am truly at peace with every single decision and action I've taken under the circumstances. I live my live knowing that my dad is watching over me.

I'm intrigued by your question about the cylinders and when I get a chance I'll snatch a couple of hubs off and see what's under there.

Charles
Charles Tate....North Mississippi

1956 WILLYS DJ3A Convertible
Doing ground up nuts and bolt restoration by almost entirely reconditioning original used or a few NOS DJ3A parts.

1962 WILLYS DJ3A Convertible. (For research and parts only)
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fredcc
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Has anyone tried one of these two stage master cylinders ?

https://onedrive.live.com/redir?resid=6ABA3...hint=file%2cpdf

Info for two stage master cylinder is on page 16
1965 DJ3 CONVERTIBLE In work
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