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#1
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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 |
#2
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Grob 103 Twin II Brake Master Cylinder
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 |
#3
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Grob 103 Twin II Brake Master Cylinder
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 |
#4
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Grob 103 Twin II Brake Master Cylinder
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 |
#5
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Grob 103 Twin II Brake Master Cylinder
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 |
#6
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Grob 103 Twin II Brake Master Cylinder
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 |
#7
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Grob 103 Twin II Brake Master Cylinder
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. |
#8
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Grob 103 Twin II Brake Master Cylinder
On Oct 22, 8:22*am, Uncle Fuzzy wrote:
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. 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- Hide quoted text - - Show quoted text - In our club Grob 103, the master cylinder is a Magura motorcycle front brake master cylinder. *Magura makes parts for a bunch of bikes, and for the aftermarket. Motorcycle front brake master cylinders come in a variety of piston diameters. *They are also somewhat weird to bleed. They won't develop pressure unless almost all of the air is bled out of the system. *"Pumping" one endlessly has no effect. *On a bike, one trick is to zip tie the handle so that the lever is halfway to the grip, crack the bleeder on the caliper (with a tube on it to direct the drainage), and walk away for a couple hours and let gravity do some work for you. *Much quicker is to zip tie the lever halfway, and use a small vacuum pump rig to PULL the fluid through. *Once most of the air is gone, you should be able to develop some pressure to complete the bleeding in the normal manner. *YES to DOT 3/4. *NO to Mil Spec 5606 hydraulic oil. *As an experiment, I tossed some motorcycle brake bits in a jar of 5606. *They turned into something other than brake bits pretty quickly.- Hide quoted text - - Show quoted text - Clarification on the quicker way to purge the air out: Zip tie the lever at half travel, use a vacuum pump ON THE CALIPER BLEEDER to pull brake fluid through. Hope this helps |
#9
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Grob 103 Twin II Brake Master Cylinder
How can one tell where to position the lever? Half way through it's total
travel or some other location? MC At 16:33 22 October 2008, Uncle Fuzzy wrote: On Oct 22, 8:22=A0am, Uncle Fuzzy wrote: On Oct 22, 8:01=A0am, "bumper" wrote: Yup, what JJ said. The "red stuff" is Mil Spec 5606 hydraulic oil and i= s compatible with Buna-N O-rings and seals. It's also commonly used in th= e 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 chang= e 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 doe= s 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 d= id fit in place. =A0Unfortunately it did not function properly. =A0It was p= roperly bled and all but it did not work. =A0I don't know what to do next. = =A0There must be at least 100 of these gliders in the US that will need a mas= ter cylinder replacement in the future. =A0I 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 believ= e they cut it down from the original, good luck getting your inspecto= r to sign off on installing it! JJ Mike McCarron wrote: My club has a 1983 Grob 103 Twin II that needs a new master cylin= der. 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- Hide quoted text - - Show quoted text - In our club Grob 103, the master cylinder is a Magura motorcycle front brake master cylinder. =A0Magura makes parts for a bunch of bikes, and for the aftermarket. Motorcycle front brake master cylinders come in a variety of piston diameters. =A0They are also somewhat weird to bleed. They won't develop pressure unless almost all of the air is bled out of the system. =A0"Pumping" one endlessly has no effect. =A0On a bike, on= e trick is to zip tie the handle so that the lever is halfway to the grip, crack the bleeder on the caliper (with a tube on it to direct the drainage), and walk away for a couple hours and let gravity do some work for you. =A0Much quicker is to zip tie the lever halfway, and use a small vacuum pump rig to PULL the fluid through. =A0Once most of the air is gone, you should be able to develop some pressure to complete the bleeding in the normal manner. =A0YES to DOT 3/4. =A0NO to Mil Spec 5606 hydraulic oil. =A0As an experiment, I tossed some motorcycle brake bits in a jar of 5606. =A0They turned into something other than brake bits pretty quickly.- Hide quoted text - - Show quoted text - Clarification on the quicker way to purge the air out: Zip tie the lever at half travel, use a vacuum pump ON THE CALIPER BLEEDER to pull brake fluid through. Hope this helps |
#10
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Grob 103 Twin II Brake Master Cylinder
Hook up vacuum pot to caliper bleed valve, open valve a turn, apply vacuum,
squeeze lever slowly until fluid flows out of bleed valve. Be sure to add fluid to reservoir as level drops. bumper "Mike McCarron" wrote in message ... How can one tell where to position the lever? Half way through it's total travel or some other location? MC At 16:33 22 October 2008, Uncle Fuzzy wrote: On Oct 22, 8:22=A0am, Uncle Fuzzy wrote: On Oct 22, 8:01=A0am, "bumper" wrote: Yup, what JJ said. The "red stuff" is Mil Spec 5606 hydraulic oil and i= s compatible with Buna-N O-rings and seals. It's also commonly used in th= e 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 chang= e 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 doe= s 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 d= id fit in place. =A0Unfortunately it did not function properly. =A0It was p= roperly bled and all but it did not work. =A0I don't know what to do next. = =A0There must be at least 100 of these gliders in the US that will need a mas= ter cylinder replacement in the future. =A0I 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 believ= e they cut it down from the original, good luck getting your inspecto= r to sign off on installing it! JJ Mike McCarron wrote: My club has a 1983 Grob 103 Twin II that needs a new master cylin= der. 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- Hide quoted text - - Show quoted text - In our club Grob 103, the master cylinder is a Magura motorcycle front brake master cylinder. =A0Magura makes parts for a bunch of bikes, and for the aftermarket. Motorcycle front brake master cylinders come in a variety of piston diameters. =A0They are also somewhat weird to bleed. They won't develop pressure unless almost all of the air is bled out of the system. =A0"Pumping" one endlessly has no effect. =A0On a bike, on= e trick is to zip tie the handle so that the lever is halfway to the grip, crack the bleeder on the caliper (with a tube on it to direct the drainage), and walk away for a couple hours and let gravity do some work for you. =A0Much quicker is to zip tie the lever halfway, and use a small vacuum pump rig to PULL the fluid through. =A0Once most of the air is gone, you should be able to develop some pressure to complete the bleeding in the normal manner. =A0YES to DOT 3/4. =A0NO to Mil Spec 5606 hydraulic oil. =A0As an experiment, I tossed some motorcycle brake bits in a jar of 5606. =A0They turned into something other than brake bits pretty quickly.- Hide quoted text - - Show quoted text - Clarification on the quicker way to purge the air out: Zip tie the lever at half travel, use a vacuum pump ON THE CALIPER BLEEDER to pull brake fluid through. Hope this helps |
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