Grob 103 Twin II Brake Master Cylinder

My club has a 1983 Grob 103 Twin II that needs a new master cylinder. Over
the years the Grob factory has made changes to the system without full
documentation and as a result the US distributor can not be sure of how I
go about purchasing the proper master cylinder for this glider.

If you or anyone you know has replaced the master cylinder on a vintage
Grob 103 Twin II recently I would appreciate your input on where I might
purchase the correct system.

Thank you,

Mike

If memory serves me, its a motorcycle master cylinder BMW? I believe
they cut it down from the original, good luck getting your inspector
to sign off on installing it!
JJ

Mike McCarron wrote:
My club has a 1983 Grob 103 Twin II that needs a new master cylinder. Over
the years the Grob factory has made changes to the system without full
documentation and as a result the US distributor can not be sure of how I
go about purchasing the proper master cylinder for this glider.

If you or anyone you know has replaced the master cylinder on a vintage
Grob 103 Twin II recently I would appreciate your input on where I might
purchase the correct system.

Thank you,

Mike

JJ,

I did purchase a master cylinder from a BMW motorcycle dealer that did fit
in place. Unfortunately it did not function properly. It was properly
bled and all but it did not work. I don't know what to do next. There
must be at least 100 of these gliders in the US that will need a master
cylinder replacement in the future. I don't see how we can junk a $30K
glider for lack of a functioning master cylinder.

Thanks for your comment,

MC

At 13:41 22 October 2008, JJ Sinclair wrote:
If memory serves me, its a motorcycle master cylinder BMW? I believe
they cut it down from the original, good luck getting your inspector
to sign off on installing it!
JJ

Mike McCarron wrote:
My club has a 1983 Grob 103 Twin II that needs a new master cylinder.
Over
the years the Grob factory has made changes to the system without full
documentation and as a result the US distributor can not be sure of
how
I
go about purchasing the proper master cylinder for this glider.

If you or anyone you know has replaced the master cylinder on a
vintage
Grob 103 Twin II recently I would appreciate your input on where I
might
purchase the correct system.

Thank you,

Mike

Why didn't it work, Mike? Hydraulics are hydraulics, the Clevland
brake slave cylinder doesn't know (or care) where that pressure is
coming from? Make sure you have compatible seals. What type fluid does
BMW use? Can't mix the red stuff with the clear stuff.
JJ

Mike McCarron wrote:
JJ,

I did purchase a master cylinder from a BMW motorcycle dealer that did fit
in place. Unfortunately it did not function properly. It was properly
bled and all but it did not work. I don't know what to do next. There
must be at least 100 of these gliders in the US that will need a master
cylinder replacement in the future. I don't see how we can junk a $30K
glider for lack of a functioning master cylinder.

Thanks for your comment,

MC

At 13:41 22 October 2008, JJ Sinclair wrote:
If memory serves me, its a motorcycle master cylinder BMW? I believe
they cut it down from the original, good luck getting your inspector
to sign off on installing it!
JJ

Mike McCarron wrote:
My club has a 1983 Grob 103 Twin II that needs a new master cylinder.
Over
the years the Grob factory has made changes to the system without full
documentation and as a result the US distributor can not be sure of
how
I
go about purchasing the proper master cylinder for this glider.

If you or anyone you know has replaced the master cylinder on a
vintage
Grob 103 Twin II recently I would appreciate your input on where I
might
purchase the correct system.

Thank you,

Mike

JJ,

I used Dot 3 fluid with compatible O ring on the slave cylinder. The cap
on the BMW master cylinder said to use DOT 3/4 brake fluid only.

MC

At 14:22 22 October 2008, JJ Sinclair wrote:
Why didn't it work, Mike? Hydraulics are hydraulics, the Clevland
brake slave cylinder doesn't know (or care) where that pressure is
coming from? Make sure you have compatible seals. What type fluid does
BMW use? Can't mix the red stuff with the clear stuff.
JJ

Mike McCarron wrote:
JJ,

I did purchase a master cylinder from a BMW motorcycle dealer that did
fit
in place. Unfortunately it did not function properly. It was
properly
bled and all but it did not work. I don't know what to do next.
There
must be at least 100 of these gliders in the US that will need a
master
cylinder replacement in the future. I don't see how we can junk a
$30K
glider for lack of a functioning master cylinder.

Thanks for your comment,

MC

At 13:41 22 October 2008, JJ Sinclair wrote:
If memory serves me, its a motorcycle master cylinder BMW? I believe
they cut it down from the original, good luck getting your inspector
to sign off on installing it!
JJ

Mike McCarron wrote:
My club has a 1983 Grob 103 Twin II that needs a new master
cylinder.
Over
the years the Grob factory has made changes to the system without
full
documentation and as a result the US distributor can not be sure of
how
I
go about purchasing the proper master cylinder for this glider.

If you or anyone you know has replaced the master cylinder on a
vintage
Grob 103 Twin II recently I would appreciate your input on where I
might
purchase the correct system.

Thank you,

Mike

The only way I ever got a Grob brake to bleed properly was to use a
pressure bleeder where fluid is forced up through the system from the
slave cylinder. Not too expensive from Spruce & Specialty.
JJ

Mike McCarron wrote:
JJ,

I used Dot 3 fluid with compatible O ring on the slave cylinder. The cap
on the BMW master cylinder said to use DOT 3/4 brake fluid only.

MC

At 14:22 22 October 2008, JJ Sinclair wrote:
Why didn't it work, Mike? Hydraulics are hydraulics, the Clevland
brake slave cylinder doesn't know (or care) where that pressure is
coming from? Make sure you have compatible seals. What type fluid does
BMW use? Can't mix the red stuff with the clear stuff.
JJ

Mike McCarron wrote:
JJ,

I did purchase a master cylinder from a BMW motorcycle dealer that did
fit
in place. Unfortunately it did not function properly. It was
properly
bled and all but it did not work. I don't know what to do next.
There
must be at least 100 of these gliders in the US that will need a
master
cylinder replacement in the future. I don't see how we can junk a
$30K
glider for lack of a functioning master cylinder.

Thanks for your comment,

MC

At 13:41 22 October 2008, JJ Sinclair wrote:
If memory serves me, its a motorcycle master cylinder BMW? I believe
they cut it down from the original, good luck getting your inspector
to sign off on installing it!
JJ

Mike McCarron wrote:
My club has a 1983 Grob 103 Twin II that needs a new master
cylinder.
Over
the years the Grob factory has made changes to the system without
full
documentation and as a result the US distributor can not be sure of
how
I
go about purchasing the proper master cylinder for this glider.

If you or anyone you know has replaced the master cylinder on a
vintage
Grob 103 Twin II recently I would appreciate your input on where I
might
purchase the correct system.

Thank you,

Mike

Yup, what JJ said. The "red stuff" is Mil Spec 5606 hydraulic oil and is
compatible with Buna-N O-rings and seals. It's also commonly used in the USA
for most small GA aircraft.

DOT automotive brake fluid, the "clear stuff", most often glycol-ether
based, and is compatible with EPDM rubber seals.

If you are switching parts from one fluid to the other, you gotta change the
rubber stuff.

bumper


"JJ Sinclair" wrote in message
...
Why didn't it work, Mike? Hydraulics are hydraulics, the Clevland
brake slave cylinder doesn't know (or care) where that pressure is
coming from? Make sure you have compatible seals. What type fluid does
BMW use? Can't mix the red stuff with the clear stuff.
JJ

Mike McCarron wrote:
JJ,

I did purchase a master cylinder from a BMW motorcycle dealer that did
fit
in place. Unfortunately it did not function properly. It was properly
bled and all but it did not work. I don't know what to do next. There
must be at least 100 of these gliders in the US that will need a master
cylinder replacement in the future. I don't see how we can junk a $30K
glider for lack of a functioning master cylinder.

Thanks for your comment,

MC

At 13:41 22 October 2008, JJ Sinclair wrote:
If memory serves me, its a motorcycle master cylinder BMW? I believe
they cut it down from the original, good luck getting your inspector
to sign off on installing it!
JJ

Mike McCarron wrote:
My club has a 1983 Grob 103 Twin II that needs a new master cylinder.
Over
the years the Grob factory has made changes to the system without full
documentation and as a result the US distributor can not be sure of
how
I
go about purchasing the proper master cylinder for this glider.

If you or anyone you know has replaced the master cylinder on a
vintage
Grob 103 Twin II recently I would appreciate your input on where I
might
purchase the correct system.

Thank you,

Mike

On Oct 22, 8:01*am, "bumper" wrote:
Yup, what JJ said. The "red stuff" is Mil Spec 5606 hydraulic oil and is
compatible with Buna-N O-rings and seals. It's also commonly used in the USA
for most small GA aircraft.

DOT automotive brake fluid, the "clear stuff", most often glycol-ether
based, and is compatible with EPDM rubber seals.

If you are switching parts from one fluid to the other, you gotta change the
rubber stuff.

bumper

"JJ Sinclair" wrote in message

...



Why didn't it work, Mike? Hydraulics are hydraulics, the Clevland
brake slave cylinder doesn't know (or care) where that pressure is
coming from? Make sure you have compatible seals. What type fluid does
BMW use? Can't mix the red stuff with the clear stuff.
JJ

Mike McCarron wrote:
JJ,

I did purchase a master cylinder from a BMW motorcycle dealer that did
fit
in place. *Unfortunately it did not function properly. *It was properly
bled and all but it did not work. *I don't know what to do next. *There
must be at least 100 of these gliders in the US that will need a master
cylinder replacement in the future. *I don't see how we can junk a $30K
glider for lack of a functioning master cylinder.

Thanks for your comment,

MC

At 13:41 22 October 2008, JJ Sinclair wrote:
If memory serves me, its a motorcycle master cylinder BMW? I believe
they cut it down from the original, good luck getting your inspector
to sign off on installing it!
JJ

Mike McCarron wrote:
My club has a 1983 Grob 103 Twin II that needs a new master cylinder.