ABS vs non-ABS front master cylinder

Riceburner

Riceburner

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Anyone know what the difference is between the two parts/assemblies?
ABS: 32727665864
non-ABS: 32727657182

I'm currently having issues bleeding up the front brakes on my Non-ABS Rockster, in fact I've had problems with the brakes for a couple of years. I have the nasty feeling that the 2nd hand m/c currently on the bike is an ABS item, but as it came from a breakers, I have no confirmation of this.

Previously, on other bikes (including my previous Rockster), I've been able to get the brakes bleed up well enough to do two-finger stoppies, on this bike I'm lucky if it passes the MOT!

The bike has a "race-style" twin braided hose (Goodridge) setup with a double banjo bolt at the m/c, and rebuilt Tokico callipers, ie all seals (including the internals) replaced last year.

I'm about "invest" in a brand new m/c direct from BMW, just to ensure that I get the right part, but I was wondering if anyone here had had any similar experiences with the m/c and if anyone knew if there is a genuine difference between the assemblies.

It's my hypothesis that the ABS m/c allows the piston to travel a set distance before it causes any pressure increase in the fluid in the pipes. This seems logical to me because it would mean that the micro-switch in the electronics is activated and thus the servo-motors turned on, before any braking-pressure is created. I think this could be done by having the two holes in the m/c body in slightly different positions, relative to the piston's seals.

Its also been my experience that without the servo-assistance, ABS fitted R259s have appalling brakes (eg when pushing the bike, ignition off).


So - any experience/knowledge out there in UKGser land? Many thanks in advance!
 
I'm no expert on this subject.

Lots of people have removed the servo's and ABS modules connecting the foot brake master cylinder to the rear brake and the front brake master cylinder directly to the front brakes without any problems. Some say the brakes perform better than before. As far as I am aware they haven't need to replace the master cylinders from ABS to non ABS, which means the amount of fluid passed by the master cylinder is not an issue

Your right about the servo brakes being pants with the ignition off. I think this is because the control circuits (handle brake and foot brake master cylinders) do not connect directly to the actuating circuits (front brake calipers and rear brake calipers) there is no transfer of fluid. They probably react across a piston in the servo unit. Though information on the internals of the servo's is sketchy.

I'm wandering if your problem isn't that your bike is far from standard. You have twice the normal length of flexible brake pipe from your master cylinder to the front calipers and you have non standard calipers. The master cylinder is designed to pass a given amount of fluid for the pull. Yours is probably not passing enough to operate your calipers over the length of hose you have. I'm not convinced that your replacement Master Cylinder will cure your problem, but I hope I'm wrong.
 
Ian J Hartley said:
I'm no expert on this subject.

Lots of people have removed the servo's and ABS modules connecting the foot brake master cylinder to the rear brake and the front brake master cylinder directly to the front brakes without any problems. Some say the brakes perform better than before. As far as I am aware they haven't need to replace the master cylinders from ABS to non ABS, which means the amount of fluid passed by the master cylinder is not an issue
Click to expand...

Yeah, I'm aware that it's been done, which does worry me that my bike is weird.

Ian J Hartley said:
Your right about the servo brakes being pants with the ignition off. I think this is because the control circuits (handle brake and foot brake master cylinders) do not connect directly to the actuating circuits (front brake calipers and rear brake calipers) there is no transfer of fluid. They probably react across a piston in the servo unit. Though information on the internals of the servo's is sketchy.

I'm wandering if your problem isn't that your bike is far from standard. You have twice the normal length of flexible brake pipe from your master cylinder to the front calipers and you have non standard calipers. The master cylinder is designed to pass a given amount of fluid for the pull. Yours is probably not passing enough to operate your calipers over the length of hose you have. I'm not convinced that your replacement Master Cylinder will cure your problem, but I hope I'm wrong.
Click to expand...

I wouldn't think that this would be the case. The callipers maybe 2nd hand, but they're from Motorworks, from another Rockster (afair), and they're identical Tokicos as fitted normally. I've fitted a brand new seal kit to them without issue. I had to source the internal seals from Kawasaki, (I split the callipers to fit the seal kit) but again - the internal seals were Tokico for Tokico callipers.

The hoses may well be longer than standard, but in hydraulics (to the best of my knowledge) that makes no difference, as long as the m/c and slave cylinders (calliper) are the same, the hoses shouldn't make a difference.
 
Hose length/layout is irrelevant. There's very little movement of fluid in a brake system, mainly transfer of pressure.

Master cylinder does seem to be the prime suspect; do you know if the bore of the m/c is the same for both servo and non-servo bikes? If the servo version is smaller, that could be your problem - it might give a longer lever travel for the same braking pressure.

All m/cs have a small hole (port) in the bore which is covered by the piston as it moves; you may have a valid point about this being in a different place on servo bikes but I suspect that this is unlikely. It would only serve to increase the lever travel and I cannot think why this would be needed.

Have you tried bleeding them from the bottom up by 'blowing' fluid upwards from the calipers with a syringe? This tends to push any air in front of it and shifts air-locks from places like banjo bolts.
 
Never had any problems when swopping the master cyclinders of a non abs/servo with an abs/servo -

But know of plenty of problems with fitting seals on tokico calipers. I won't fit seals as i can do without the continual problems ;)
 
littleredrooster said:
Have you tried bleeding them from the bottom up by 'blowing' fluid upwards from the calipers with a syringe? This tends to push any air in front of it and shifts air-locks from places like banjo bolts.
Click to expand...

Yup - repeatedly.

Steptoe - I'm aware that the internal seals on Tokicos can cause issues - which is why I specifically sought out new ones from a Kawasaki supplier. I've replaced the internal seals on Tokicos a couple of times - it's never caused issues as long as new seals are used. (the real trick is to clean up the mating surfaces to ensure that the seals are clamped solidly).
 
You fitted a SH master cylinder from a breakers, you've never been able to get it to firm up as such??.........

I'm no great wiz at all this, but surely you could have just fitted another faulty or at the very least well worn master cylinder!!

Thought beemer master cylinders were serviceable? Sure my first RS had an overhaul as part of the dealers prep before I bought it. So why dont you just overhaul it? :nenau
 
Littledumptruck said:
You fitted a SH master cylinder from a breakers, you've never been able to get it to firm up as such??.........

I'm no great wiz at all this, but surely you could have just fitted another faulty or at the very least well worn master cylinder!!

Thought beemer master cylinders were serviceable? Sure my first RS had an overhaul as part of the dealers prep before I bought it. So why dont you just overhaul it? :nenau
Click to expand...

I have. :)

I overhauled it when I put it on initially, and I'm sure I've overhauled it again since.

Hence why I'm finally splashing out on a new complete assembly from BMW.
 
First ride post servoectomy to try the brakes, ran a stoppie into the pub car park whist stopping for a quickie on the way home. Just as a test you understand! Not enough feel for me with the servo to do that and ABS would have fretted about it. Obviously brakes ( or more popularly breaks) work really well and feel much more progressive and controllable without the servo. Cant imagine why i put up with all the whining and fretting before. ( Then, some people stay married and seem to enjoy that sort of thing.)
 
Well, as you all surmised, the replacement m/c hasn't made any difference!

I still feel happier to have a new m/c, piston, micro-switch* & lever etc

The only other thing I can think of is to replace the calliper internal seals again. :(






* it was getting badly worn.
 
You've probably tried this already, but as you have a complete parallel system from the master cylinder onwards, Have you tried half splitting the system by disconnecting one complete side to see if you can firm up the brakes individually. It might help you diagnose if it is a caliper thats causing the problems, before you start stripping them down.

I'm not advocating you test ride the brakes, but you should be able to make a static comparison to aid you in you fault diagnosis.
 
Ian J Hartley said:
You've probably tried this already, but as you have a complete parallel system from the master cylinder onwards, Have you tried half splitting the system by disconnecting one complete side to see if you can firm up the brakes individually. It might help you diagnose if it is a caliper thats causing the problems, before you start stripping them down.

I'm not advocating you test ride the brakes, but you should be able to make a static comparison to aid you in you fault diagnosis.
Click to expand...
I was thinking about trying that....
 
If you don't find anything wrong with the calipers, you might want to consider fitting a double banjo bolt with a bleed nipple, just in case you are getting a small air bubble trapped in the banjo. It's wild considering you've bled from the bottom up, but a small price to pay if it solves your problem.
 
Just a thought.

In a past life, I have known people who had problems after changing calipers.

Could not get any brakes.

Eventually, it turned out that they had mixed up the calipers, and fitted them with the bleed nipples facinf downwards instead of upwards. As a consequence, the brakes were unbleedable, with air pockets trapped in the calipers.
Just a thought.
Myke
 
Myke Rocks said:
In a past life, I have known people who had problems after changing calipers.

Could not get any brakes.

Eventually, it turned out that they had mixed up the calipers, and fitted them with the bleed nipples facinf downwards instead of upwards. As a consequence, the brakes were unbleedable, with air pockets trapped in the calipers.
Just a thought.
Myke
Click to expand...
Weird, how did they manage that?
 
Easy.

Riceburner said:
Weird, how did they manage that?
Click to expand...

This was on a very early Audi 100 with inboard disks. Gerabox was rebuilt, and afterwards they put the left caliper in the right & vise versa.
You could do the same with most motorcycles.

Myke
 
Thanks for all the suggestions & advice.

I've cracked 'em :D

Someone on another forum suggested that if the weather seals were full of crud they would be prevented from advancing properly and thus you'd never get any proper pressure build up. Thought about it and the logic seemed correct. So i popped each piston individually, stripped out the weather seals, which were ALL full of white gack & dust. And as I progressed the pressure came back into the system! Brakes are now brilliant!

For the future I'm going to look into fitting either the Brembo callipers that were the alternative factory fitting, or potentially a pair of Nissins.
 
Riceburner said:
Yup - repeatedly.

. I've replaced the internal seals on Tokicos a couple of times - it's never caused issues as long as new seals are used. (the real trick is to clean up the mating surfaces to ensure that the seals are clamped solidly).
Click to expand...

Riceburner said:
So i popped each piston individually, stripped out the weather seals, which were ALL full of white gack & dust. .
Click to expand...

This is exactly why i'm more reluctant to offer advise anymore. :D
 
Steptoe said:
This is exactly why i'm more reluctant to offer advise anymore. :D
Click to expand...

It wasn't the internals, it was the weather seals. :)


Didn't mean to make it sound like I wasn't listening to you, I've just not seen the Tokico weather seals cause this issue before, and I've had plenty of gacky weather seals in the past 18-19 years running Tokicos all year round. :) (12 years on a ZXR400, the past 6 on the Rocksters).
 
Nippy Normans supply Touratech, Wunderlich, Desert Fox and many other makes of accessories.
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