Rear Brake

[Nobbyk]

Should I be able to lock the rear wheel up with ABS? I have noticed that this can happen occassionally when I'm not exactly 'standing' on the brake pedal

It has been serviced accordingly and has done 2000 since the last. It doesn't worry me too much, I'm just concerned whether the ABS is working as it was intended

Any thoughts?

Nobbly

 

[ebbo]

ABS switches off below a certain speed (5/10mph?) or you wouldn't be able to stop, so yes, you can lock the back wheel (or front) if your going slow enough

 

[Nobbyk]

Thanks

 

[ScaryAardvark]

I just locked the back wheel up this morning... Was a bit aggressive with the down shifts and clutch release.. (I was in a hurry )

Got a bit of a wiggle on but dipped the clutch and all was well..

At least it gave the people in the bus shelter something to talk about at work this morning

 

[Brian ROSEN]

"Was a bit aggressive with the down shifts" ....so in fact it ould be nothing at all to do with brakes/ABS.

 

[AdamA]

ABS switches off below a certain speed (5/10mph?) or you wouldn't be able to stop

Eh?

Why wouldn't you be able to stop?

 

[Brian ROSEN]

Eh?

Why wouldn't you be able to stop?

Sensors on the wheel transmit rotation speed to the control system and release the pressure if the wheel ceases to rotate.

 

[AdamA]

Sensors on the wheel transmit rotation speed to the control system and release the pressure if the wheel ceases to rotate.

Surely the control system looks at the difference in rotational speed, therefore as long as both wheel's stopped at the same time it's a non issue.

 

[Brian ROSEN]

Surely the control system looks at the difference in rotational speed, therefore as long as both wheel's stopped at the same time it's a non issue.

Yes, I thought you would say that! As I understand it (and I may be wrong) the system on on a bike simply prevents a wheel 'locking up.' (On a car it is of course necessary for all four wheels to be rotating evenly and thus there is a comparison of rotatioonal speeds.)

 

[AdamA]

Yes, I thought you would say that! As I understand it (and I may be wrong) the system on on a bike simply prevents a wheel 'locking up.' (On a car it is of course necessary for all four wheels to be rotating evenly and thus there is a comparison of rotatioonal speeds.)

So a wheel has to actually lock for the ABS to kick in?

 

[Brian ROSEN]

So a wheel has to actually lock for the ABS to kick in?

No of course not. I should have said...." and release the pressure if the wheel is about to cease to rotate." ( I hesitate to confess that I do not really know how it all works - these are my assumptions!)

 

[AdamA]

No of course not. I should have said...." and release the pressure if the wheel is about to cease to rotate." ( I hesitate to confess that I do not really know how it all works - these are my assumptions!)

K, so basically you are making it up?

Cool.

Sooooo....


This system that doesn't, in your made up opinion, monitor the differences in rotational speeds between the front and rear wheels, how does it tell that one or other wheel is "about to" lock up.

 

[Brian ROSEN]

."... so basically you are making it up?" Well no,not really. I confess that I was just putting down what it says in the Haynes Manual Page 5.16. If you have not got this book it is only £15 post free from Nippy Norman (and well worth it.).

 

[AdamA]

."... so basically you are making it up?" Well no,not really. I confess that I was just putting down what it says in the Haynes Manual Page 5.16. If you have not got this book it is only £15 post free from Nippy Norman (and well worth it.).

I might in a couple of years when the warranty runs out. Cheers.
I generally don't hold too much stead in what Haynes have to say tho.
Rather get hold of a BMW workshy manual.


So, how do Haynes say it tells that one or other wheel is "about to" lock up?

 

[Brian ROSEN]

So, how do Haynes say it tells that one or other wheel is "about to" lock up? ....." a sensor on each wheel transmits wheel speed information to the ABS control unit. If the control unit senses that a wheel is about to lock up the pressure modulator releases brake pressure momentarily to that wheel, preventing a skid;"
It is now past my bedtime and I will look into the BMW Workshop manual on Monday. Bon soir.

 

[hops]

sorry brian

but the fact a bike has ABS has no real relevance to it being able to stop or not. The ABS does not operate all the time & only allows a degree of steering to be applied under heavy braking i.e. when the control unit senses a wheel about to lock. The system used on our bikes is not exactly hi-tech and therefore when it is in operation the wheel is braked and released at a slower rate to modern systems. This can lead to a momentary locking of the wheel & the sensation you possibly felt.

 

[AdamA]

So, how do Haynes say it tells that one or other wheel is "about to" lock up? ....." a sensor on each wheel transmits wheel speed information to the ABS control unit. If the control unit senses that a wheel is about to lock up the pressure modulator releases brake pressure momentarily to that wheel, preventing a skid;"

"If the control unit senses that a wheel is about to lock up"
Doesn't really answer the question "how?" does it?

The only way it can sense a possible lock up starting is if one wheel slows much quicker than the other. If it did not compare the two wheel speeds it would simply see a wheel slowing down to a stop.
Ergo it must look "at the difference in rotational speed, therefore as long as both wheel's stopped at the same time it's a non issue".

Methinks Haynes are somewhat oversimplifying the system.

It is now past my bedtime and I will look into the BMW Workshop manual on Monday. Bon soir.

Guten nacht.

 

[AndyT]

Should I be able to lock the rear wheel up with ABS? I have noticed that this can happen occassionally when I'm not exactly 'standing' on the brake pedal

It has been serviced accordingly and has done 2000 since the last. It doesn't worry me too much, I'm just concerned whether the ABS is working as it was intended

Any thoughts?

Nobbly

When I first got my R1150GSA Se which is fitted with Servo brakes I had a few instances of the rear wheel locking up sometimes at high speed when cranked over (very unsettling). I was talking to a BMW technician in Belgium when one of the 1200's had failed due to the dreaded EWS failure and mentioned this. He said that there had been a recall to fit an orifice into the rear brake line on servo bikes as the wheel can lock up when ridden solo without luggage. My bike to my knowledhe has never been recalled and in the UK BMW have never acknowledged this
I am very careful on the rear brake now but ironically enough I need new front pads

AndyT

 

[Big Lee]

I`m sure I`ve locked my back wheel up while "testing" the ABS It was just for a split second while the computer sorted its self. I could be wrong though but it felt like it

 

[Brian ROSEN]

"......but the fact a bike has ABS has no real relevance to it being able to stop or not. "
No, just whether it stops in a vertical position or a horizontal one!