ABS on R1150RT

[AndyS]

Can anyone explain or direct me to some documentation that will explain in simple terms how the ABS system on this model works?

I understand the principles of ABS, but it is how it marries in with the Servo brakes. How are they switched on etc?

Cheers

Andy

[Jerry Duke]

Does this help?

http://www.bmwscruz.com/motorcycles/current/tech_abs.html

[AndyS]

Does this help?

 

Thanks Jerry, I understand the principles, it's more the detail - the sort of nuts and bolts of the system....say of what starts the Servo's (for instance). Do they use brake line pressure to start the pumps or do they use the brake lever micro switches. Do the servos get get any other controlling inputs etc.

 

 

Cheers

 

Andy

[DrPaul]

Andy,

As I understand, the servo motors are actuated by the microswitches at the front lever and/or the rear pedal.

[T__]

Andy, the year of the I-ABS system makes a difference on servo pump operation..

 

On ALL (fully linked) I-ABS systems either the front or rear brake switch starts both servo pumps (unless a non linked system, then only the end used starts).. In fact the ABS controller is what actually turns the brake light on.. The lever/pedal switches are actually reverse logic.. On the later (fully linked) I-ABS systems the rear servo actually turns off when fully stopped & low rear input control pressure..

After the servos gets their power (internal electronics actually turn them on) they then power up & start pumping fluid through the controller valves & control system.. It basically just pumps open circuit through the system & back into the internal reservoir..

 

This open circuit fluid pressure basically just flows out through open balls & seats..

When a fluid pressure is input from either or both (front or rear) control circuits (ie stepping on the rear brake or pulling the front lever) is input onto the controller valve area it starts seating those balls.. As the balls are seated they start closing off the servo flow back to the reservoir & force it to apply hydraulic pressure to the apply pistons that pressurize the wheel circuits.. The more “control side” pressure (from the rider) the more those balls & seats close off the more servo apply pressure is applied to the wheel circuit pistons.. In an ABS event the ABS controller takes over & dumps the apply pressure off as needed to keep a wheel from locking..

 

You are asking about the ABS system on the 1150 so we won’t go into the servo assist part of the brake system much more than that..

 

Twisty

 

 

[AndyS]

Thanks for your responses. Part of the reason for the question was a subject that came up on a UK site.

The bike is an R1150R.

A chap went out for a ride - read on to see what happened.

This kind-of sent a chill down my spine.

So here's his story....

"3 miles into a trip, the brakes came on and we came to a sliding stop. luckily, we had just starting to go up a hill, and was doing about 20mph. abs failure light and warning light were lit. i dont know why, but wish i had not, took the bike to the bottom of the hill and along a small stretch, to see if i could fathom what had happened, only to return to my waiting other half, taking a left back up the hill and during a change into 2nd gear, exactly the same thing happened. unfortunately, i wasnt able to stay on the bike, and has left me with rather large cuts to the legs."

 

I can't see why the ABS wouldn't have over-ridden a 'Servo On' signal.

Any thoughts?

Andy

 

[T__]

Andy, there is something missing from that story.. The ABS (more correctly the servo brake system) won’t just turn itself on & apply the brakes..

 

It’s possible you just have a tale teller on the other end of your thread,, or an ABS system basher,, or something is contacting the brake pedal or hand lever,, or engine stall & feels like brakes,, or even poor rider bike control,, or more to the issue than told..

 

I do suppose the brake controller vent line(s) could be plugged & given enough heat expansion could drag a brake a little.. But full apply (no way)---& nothing to do with the power servo or ABS part..

 

Twisty