Author Topic: Aftermarket Rear Master Cylinder Replacement Guide $10-$25  (Read 25107 times)

Offline YoungEngineer

  • ^ Motobrick Curious
  • Posts: 109
Aftermarket Rear Master Cylinder Replacement Guide $10-$25
« on: January 25, 2017, 04:05:20 PM »

This guide explains how to replace the stock Brembo rear master cylinder with a universal (Chinese) clone for a minimal cost.
The total cost of this conversion is less then the cost of replacing the seals on the stock Brembo which are now becoming very rare.

I cannot certify the quality or how long the aftermarket rear MC will last, again its a Chinese clone which is better then having no rear brakes at all (My current situation).
I would never recommend using non genuine parts for the front brakes but the rear in my opinion is not an issue due to its infrequent use.


Total cost of conversion if not using ABS is around $10-$15. If using ABS then around $25 should be expected due to the use of fitting reducers on the ABS pump.


Universal Master Cylinder


UK
USA


Thread Adapter M12x1 to M10x1 (For ABS users only)



UK
USA


Braided Brake Line (Any brake line will do over 70CM, best to find one with a 90o Right angle, I found mine used for very cheap)


UK


Banjo Bolt M10 x 1 (ABS users only)


UK
USA(Cannot find any on Ebay, Maybe they are called something different over there)



1. Remove rear-set, four bolts total, don't forget the brake line, the brake sensor and the reservoir tube
2. Remove the existing Brembo Master cylinder, two bolts, one is under spring tension so remember to compress the spring so that it comes out straight. 
3. Remove the existing ball-joint coupling on the inside of the brake lever using a 13mm spanner, we will no longer use it as the new MC has an internal one.
4. Remove the new master cylinder from the packaging and cut the threaded bolt in half using a hacksaw, Do not use an angle grinder as the heat will damage the seals.
5. Use a file to file down the end of the threaded bar and make sure it is smooth with no swarf.
6. Thread the bar into the threaded hole, spin the MC intil the rear holes line up and re-insert the bolts.
7. If using the an ABS system, remove the OEM steel brake line from the ABS pump, replace with a standard flexible brake line instead. You will need to now insert the M12x1 to M10x1 fitting reducer.
8. Fasten the brake hose to the ABS pump using a M10x1 Banjo bolt, fasten the other side to the rear MC using the supplied M10x1.2 banjo bolt.
  • London
  • K1100LT
Agree Agree x 1 View List

Online Martin

  • ^ Quintessential Motobricker
  • Posts: 3872
Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
« Reply #1 on: January 25, 2017, 05:21:14 PM »

Thanks for the information much appreciated especially due to the cost of one in OZ. For OZ buyers it is available on AliExpress https://www.aliexpress.com/item/Audew-Universal-Rear-Motorcycle-Dirt-Pit-Bike-Hydraulic-Master-Oil-Brake-Reservoir-Cylinder-Gold/32601326433.html?
Regards Martin.
  • North Lakes Queensland Australia
  • 1992 K75s Hybrid, Lefaux, Vespa V twin.

Offline Motorhobo

  • 18 years of K75
  • ^ Quintessential Motobricker
  • Posts: 1456
Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
« Reply #2 on: January 27, 2017, 08:39:19 AM »
Someone should put this in the Lieberry. Please keep us updated if you have any issues in the future. The price of a new OEM rear MC is out of control and used isn't really much of an option.
1994/1995 K75 ABS Frankenbike: original engine 130k miles, frame from Gary Weaver (RIP), 173k miles -- Current Odometer: 184k miles
1994 K75 since 2013, 76,000 mi (11k mine) w/California Sidecar Friendship II Sidecar & Black Lab 'Miss B'

Past: 1974 Honda 550/4 (first bike), 1994 K75 (sold), 1995 K75 ABS (parts bike), Sidecar Dog & Best Bud 'Bo' - RIP

Offline YoungEngineer

  • ^ Motobrick Curious
  • Posts: 109
Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
« Reply #3 on: January 27, 2017, 08:51:39 AM »
If there is more interest I may make a step by step video. However its simple enough to not need one.


I've been using this conversion for a little over a week now and it works great. The rear brake is far more responsive then the stock one, its easy to lockup the back wheel with minimal pressure.
  • London
  • K1100LT

Offline The Mighty Gryphon

  • ^ Quintessential Motobricker
  • Posts: 4596
Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
« Reply #4 on: January 27, 2017, 10:08:58 AM »
I just purchased one of these master cylinders for my K75RT.   Ever since I bought it 3 years ago the rear brake hasn't worked worth a shyt.  After buying a used cylinder, two rebuild kits and resleeving I'm done screwing around.   

It should be here in late February and I'll be reporting on how the installation goes.  I'm looking forward to seeing if I can trigger the ABS on the rear wheel on that bike.  It will be a totally new experience.   

There are a couple of things I'm curious about with this cylinder.  One of them is the long term effect of mounting the cylinder upside down with the hose to the reservoir coming in at the bottom of the cylinder.  As long as the reservoir is high above the cylinder it should be ok, but only time will tell.   Another is the linkage to the brake pedal.  I wonder what the lack of articulation there will do to side loading the seals and piston in the bore of the cylinder.   It's something I plan on looking at closely when I do the installation.

On a side note, it's disgusting the way BMW prices spares.  $255 for an assembly that I just purchased for $7 on eBay is beyond robbery.  Really, it's just a freaking die casting with a screw machine made piston and a handful of rubber and plastic bits. 
  • In my garage in Marilla, NY
  • '94 K75RT Mystic Red, '91K100RS White/Blue, '89 K100RS Special edition White/Blue
Current:
'94 K75RT "Ilsa, She Wolf of the SS"
'91 K100RS "Moby Brick Too
'89 K100RS SE

Offline Laitch

  • ^ Quintessential Motobricker
  • Posts: 6932
Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
« Reply #5 on: January 27, 2017, 10:13:53 AM »
The rear brake is far more responsive then the stock one, its easy to lockup the back wheel with minimal pressure.
I'd rather have a rear brake that I can use with finesse while on a bumpy, downhill gravel road run. Touchy rear brake response isn't appealing to me under those conditions.
  • Along the Ridley in Vermont.
  • 1995 K75 72,000 miles
I wept because I had no radials until I met a man who had no splines.
http://www.motobrick.com/index.php/topic,296.msg53303.html#msg53303

Offline YoungEngineer

  • ^ Motobrick Curious
  • Posts: 109
Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
« Reply #6 on: January 27, 2017, 10:20:51 AM »
I just purchased one of these master cylinders for my K75RT.   Ever since I bought it 3 years ago the rear brake hasn't worked worth a shyt.  After buying a used cylinder, two rebuild kits and resleeving I'm done screwing around.   

It should be here in late February and I'll be reporting on how the installation goes.  I'm looking forward to seeing if I can trigger the ABS on the rear wheel on that bike.  It will be a totally new experience.   

There are a couple of things I'm curious about with this cylinder.  One of them is the long term effect of mounting the cylinder upside down with the hose to the reservoir coming in at the bottom of the cylinder.  As long as the reservoir is high above the cylinder it should be ok, but only time will tell.   Another is the linkage to the brake pedal.  I wonder what the lack of articulation there will do to side loading the seals and piston in the bore of the cylinder.   It's something I plan on looking at closely when I do the installation.

On a side note, it's disgusting the way BMW prices spares.  $255 for an assembly that I just purchased for $7 on eBay is beyond robbery.  Really, it's just a freaking die casting with a screw machine made piston and a handful of rubber and plastic bits.


It should be easy to trigger the ABS. I replaced my rear pads as well as installed a new braided brake hose and after bleeding and bedding in the new pads (holding down the rear brake pedal at 30Mph for a few hundred feet at a time) the rear wheel will lock with minimal pressure. I think it may even be more responsive then the front brakes its quite surprising. Calipers are retracting as normal and not sticking to the disc.


As for the sideways load, this was one of my concerns however this MC is built differently to the OEM one. The stock Brembo uses a ball-joint type coupling between the pedal and the MC to provide that articulation. The universal MC has this ball joint built into it so has internal articulation providing quite a bit of movement.






  • London
  • K1100LT

Offline YoungEngineer

  • ^ Motobrick Curious
  • Posts: 109
Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
« Reply #7 on: January 27, 2017, 10:23:30 AM »
I'd rather have a rear brake that I can use with finesse while on a bumpy, downhill gravel road run. Touchy rear brake response isn't appealing to me under those conditions.


I agree, however you become very used to the new sensitivity. I can ride just fine without locking the back, but now instead of using my entire leg I just use my toes. Its just as controllable it just requires less force. Its just like riding a modern sportsbike.
  • London
  • K1100LT

Offline Laitch

  • ^ Quintessential Motobricker
  • Posts: 6932
Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
« Reply #8 on: January 27, 2017, 10:24:37 AM »
$255 for an assembly that I just purchased for $7 on eBay is beyond robbery. 
It doesn't approach being robbery when $7 alternatives are available. It's just plain old supply-and-demand capitalism.
  • Along the Ridley in Vermont.
  • 1995 K75 72,000 miles
I wept because I had no radials until I met a man who had no splines.
http://www.motobrick.com/index.php/topic,296.msg53303.html#msg53303

Offline Laitch

  • ^ Quintessential Motobricker
  • Posts: 6932
Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
« Reply #9 on: January 27, 2017, 10:29:57 AM »
I can ride just fine without locking the back, but now instead of using my entire leg I just use my toes.
Great! Please continue the updates regarding the effectiveness of your modifications when you're on the 10,000 miler.
  • Along the Ridley in Vermont.
  • 1995 K75 72,000 miles
I wept because I had no radials until I met a man who had no splines.
http://www.motobrick.com/index.php/topic,296.msg53303.html#msg53303

Offline YoungEngineer

  • ^ Motobrick Curious
  • Posts: 109
Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
« Reply #10 on: January 27, 2017, 10:53:36 AM »

Great! Please keep continue the updates regarding the effectiveness of your modifications when you're on the 10,000 miler.




Yes, well of course they may be my downfall, however in the name of science I am happy to play guinea-pig.
  • London
  • K1100LT

Offline The Mighty Gryphon

  • ^ Quintessential Motobricker
  • Posts: 4596
Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
« Reply #11 on: January 27, 2017, 11:10:44 AM »
The ball joint at the end of the piston doesn't look like it will accommodate the arc the linkage will go through on my K75.   Right now, I'm trying to find a way to allow the connection at the pedal to rotate.  I'm leaning toward a Heim joint or a threaded pin to receive the rod from the master cylinder.  Either way, it means a non reversible modification to the pedal.   

Have you been able to look at the joint on the master cylinder?  Can it be disassembled? 
  • In my garage in Marilla, NY
  • '94 K75RT Mystic Red, '91K100RS White/Blue, '89 K100RS Special edition White/Blue
Current:
'94 K75RT "Ilsa, She Wolf of the SS"
'91 K100RS "Moby Brick Too
'89 K100RS SE

Offline Laitch

  • ^ Quintessential Motobricker
  • Posts: 6932
Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
« Reply #12 on: January 27, 2017, 11:14:13 AM »
Yes, well of course they may be my downfall, however in the name of science I am happy to play guinea-pig.
I'm not contending that it will be your downfall, gravity will take care of that—if you're like the rest of us. :giggles 
Your selfless dedication to science will be revered among motorcycle parts consumers and your name will be spoken with hushed awe around tire changing machines and grease barrel fires worldwide.
 :clap:
  • Along the Ridley in Vermont.
  • 1995 K75 72,000 miles
I wept because I had no radials until I met a man who had no splines.
http://www.motobrick.com/index.php/topic,296.msg53303.html#msg53303

Offline YoungEngineer

  • ^ Motobrick Curious
  • Posts: 109
Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
« Reply #13 on: January 27, 2017, 11:25:23 AM »
Have you been able to look at the joint on the master cylinder?  Can it be disassembled?


I've not dissembled it I'm afraid, I just made an assumption based on the free movement the threaded rod had.


I would assume the ball joint coupling is like this.


  • London
  • K1100LT

Offline YoungEngineer

  • ^ Motobrick Curious
  • Posts: 109
Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
« Reply #14 on: January 27, 2017, 11:28:30 AM »
I'm not contending that it will be your downfall, gravity will take care of that—if you're like the rest of us. :giggles 
Your selfless dedication to science will be revered among motorcycle parts consumers and your name will be spoken with hushed awe around tire changing machines and grease barrel fires worldwide.
 :clap:


lol
  • London
  • K1100LT

Offline YoungEngineer

  • ^ Motobrick Curious
  • Posts: 109
Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
« Reply #15 on: January 27, 2017, 11:34:32 AM »
This is the closet looking setup I have seen. As you can see the threaded bolt has a ball-end and there is a socket/cup which would sit above the piston. So there shouldn't be any issue with side loading on the seals.


  • London
  • K1100LT

Offline The Dude

  • ^ SuperNatural Motobricker
  • Posts: 509
Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
« Reply #16 on: January 27, 2017, 01:34:18 PM »
Nice work young Engineer.
"but the rear in my opinion is not an issue due to its infrequent use."
Mmmm,you ABS ers!
Rectify this bad habit.Best use both front and rear together.(that'll be the official line) Unless,as Laitch pointed out,your on gravel or ice and more so down hill to prevent the front wheel burying itself in a world of pain.Oh and wheelies,of course... :falldown:
Keep it coming.
  • Auckland, New Zealand
  • K75s
Current.
TR6R 1973 from new.
Moto guzzi 850 III .1983 from,almost, new.
K75S 1986 from new.vin-0103141
On my second millionth km.give or take a hundred k Kay's.
"The Dude abides. I don't know about you but I take comfort in that. It's good knowin' he's out there."
All the best!

Offline The Mighty Gryphon

  • ^ Quintessential Motobricker
  • Posts: 4596
Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
« Reply #17 on: January 27, 2017, 02:23:01 PM »
I have eyeballed the pedal geometry on my K75 and it looks like the end of the actuator shaft in the master cylinder will swing through an arc of at least 10mm, possibly more.  Unless there is the ability of the shaft to work over the entire diameter of the piston there will probably be some significant side loading.  It also requires a very careful setup of the pedal position to keep the arc close to centered on the end of the piston.

By allowing the pedal end to pivot, the shaft can stay centered on the piston and remove any side loading regardless of the pedal position.  That was the reason for the link which was removed to work on your bike.  That articulation at the pedal is what I hope to achieve with my installation.
  • In my garage in Marilla, NY
  • '94 K75RT Mystic Red, '91K100RS White/Blue, '89 K100RS Special edition White/Blue
Current:
'94 K75RT "Ilsa, She Wolf of the SS"
'91 K100RS "Moby Brick Too
'89 K100RS SE

Online Martin

  • ^ Quintessential Motobricker
  • Posts: 3872
Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
« Reply #18 on: January 27, 2017, 03:08:00 PM »

I'd like to see one disassembled for a couple of reasons, the articulation factor, and the piston type and location. If the type and location of the cups is the same as the OEM one, it might be possible to use the OEM housing with the Chinese piston and cylinder. I do realise that the chances are highly unlikely, but it would be nice to find a cheap source of compatible pistons and cups. The Chinese bore size is 12.87 mm one of the OEM's is 13mm a difference of .13, it might be worth a look.   I remember when it was possible to go into a clutch and brake specialist and just buy the cups. I used to race Go Karts and I bought one with a stuffed brake master cylinder. A mate bored it out and machined up a new piston and we bought new cups from a brake specialist, now no longer possible. I kitted mine not long ago, but might get a Chinese one to play with.
Regards Martin.
  • North Lakes Queensland Australia
  • 1992 K75s Hybrid, Lefaux, Vespa V twin.

Online Martin

  • ^ Quintessential Motobricker
  • Posts: 3872
Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
« Reply #19 on: January 27, 2017, 05:52:18 PM »

Due to the unavailability of master cylinder kits from Beemer Boneyard and the cost of OEM kits and cylinders.  Spurred on  by the Young engineer I decided to do a bit more research. I believe that some model Ducati's and Moto Guzzi's were equipped with 13mm rear brake cylinders. There is a Ducati specialist in SO Cal  https://store.bevelheaven.com/index.php?p=home might be worth somebody local checking. I also found this on Ebay http://www.ebay.com.au/itm/New-Moto-Guzzi-Brembo-13mm-Silver-Rear-Brake-Master-Cylinder-Pump
Regards Martin.
  • North Lakes Queensland Australia
  • 1992 K75s Hybrid, Lefaux, Vespa V twin.

Online Martin

  • ^ Quintessential Motobricker
  • Posts: 3872
Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
« Reply #20 on: January 28, 2017, 04:20:37 PM »

Possible replacement for UK buyers  http://www.ebay.com.au/itm/Brembo-OE-Rear-Brake-Master-Cylinder-11mm-In-Line-Exit-Black
Performoto have heaps of Brembo master cylinders different configurations at very reasonable prices compared to OEM. Would be nice if a UK inmate could find out if they have a direct replacement and post the answer.

Business seller information

Performoto

             Contact details         



Adam Jordan
30 Gay Street
Bath
Somerset
BA1 2PA
United Kingdom

  • North Lakes Queensland Australia
  • 1992 K75s Hybrid, Lefaux, Vespa V twin.

Online Martin

  • ^ Quintessential Motobricker
  • Posts: 3872
Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
« Reply #21 on: February 10, 2017, 04:26:13 AM »

I've also been looking at a couple more, hole spacing at 50mm compared to OEM 45mm, but they have the same location of the reservoir inlet between the mounting holes. http://www.ebay.com.au/itm/Rear-Brake-Master-Cylinder-Fit-Yamaha-WR250-1991-1997-YZ250WR-1990-WR500-1992-93/171911367557?   or  https://www.aliexpress.com/item/Universal-Motorcycle-Dirt-Pit-Sport-Bike-ATV-Foot-Rear-Brake-Master-Cylinder-Hydraulic-Pump-For-Kawasaki/32720693329.html?  Honda, Suzuki, Yamaha all have similar M/Cyl with the reservoir inlet between the mounting holes but the mounting holes are 50mm apart, I will do some more research before I actually order one, I'm trying to borrow an old foot peg plate and OEM M/Cyl to play with.
Regards Martin
  • North Lakes Queensland Australia
  • 1992 K75s Hybrid, Lefaux, Vespa V twin.

Offline The Mighty Gryphon

  • ^ Quintessential Motobricker
  • Posts: 4596
Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
« Reply #22 on: February 10, 2017, 08:43:24 AM »
I have some ideas for the originally posted master cylinder that will make for a neat, easily reversible installation if it doesn't work.   Looking forward to getting the parts that are coming on a slow boat from China.
  • In my garage in Marilla, NY
  • '94 K75RT Mystic Red, '91K100RS White/Blue, '89 K100RS Special edition White/Blue
Current:
'94 K75RT "Ilsa, She Wolf of the SS"
'91 K100RS "Moby Brick Too
'89 K100RS SE

Offline YoungEngineer

  • ^ Motobrick Curious
  • Posts: 109
Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
« Reply #23 on: February 10, 2017, 09:28:49 AM »
I have some ideas for the originally posted master cylinder that will make for a neat, easily reversible installation if it doesn't work.   Looking forward to getting the parts that are coming on a slow boat from China.


I don't see why everyone is so concerned about the reservoir tube being at the bottom. It works fine for me, in-fact I'm still using the original reservoir with the stock tube, its a bit of a stretch I admit.
  • London
  • K1100LT

Offline Laitch

  • ^ Quintessential Motobricker
  • Posts: 6932
Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
« Reply #24 on: February 10, 2017, 09:46:19 AM »
I don't see why everyone is so concerned about the reservoir tube being at the bottom.
For the record, I'm not concerned.

You're doing research that is helpful.
  • Along the Ridley in Vermont.
  • 1995 K75 72,000 miles
I wept because I had no radials until I met a man who had no splines.
http://www.motobrick.com/index.php/topic,296.msg53303.html#msg53303

Tags: