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Thread: ABS-II Activating Prematurely

  1. #1
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    ABS-II Activating Prematurely

    My K has been in the shop for the past few weeks so I've been riding the R1100RSL back and forth to work. This is the first stop and go traffic situation I've been in on this bike since I completed the refurbishment earlier this year.

    The ABS-II system is activating at what I consider below threshold braking. This is straight line quick braking from 40-50 miles an hour.

    Is ABS-II known for being over sensitive?

    Would the set of braided stainless steel brake lines I installed changed the ABS threshold?

    Is an adjustment possible?

    I really do not like it and am considering a by pass.

    Thoughts?

  2. #2
    rabid reader dbrick's Avatar
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    I rode a 1996 R1100RSL with ABS for thirteen years, and have never heard of the system activating too easily. When I first bought the bike I deliberately invoked it to make sure it worked; in the years after, it only went off on its own once as I was braking over wet/dirty/uneven pavement (a construction leftover) approaching a traffic signal at low speed.

    I installed stainless steel brake lines almost immediately upon purchasing the bike, and they had no effect other than significantly improving the lever feel.
    David Brick
    Santa Cruz CA
    2007 R1200R

  3. #3
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    I appreciate the feedback. Well, I may have a problem with the ABS unit itself. I wonder is there is a diagnostic check the dealer can perform?

  4. #4
    rabid reader dbrick's Avatar
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    You're welcome.

    I don't know what info can be retrieved by a dealer with its equipment. Doing an A-B comparison with another rider and bike might be useful.
    David Brick
    Santa Cruz CA
    2007 R1200R

  5. #5
    Nickname: Droid
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    We need more definition to determine what you mean by "premature activation". Do you feel the ABS cycling (pulsing action of the bike) or is it simply the ABS pump cycling (which it does normally) as part of its operation.
    Is this with both brakes applied? Rear brake only? Front brake only? Does it react on a totally smooth surface (no cracks or steps on the surface), or does it seem to do it only on cracked/stepped surfaces?

    I'm guessing here, but does it happen most often with the rear brake applied (with or w/o front brake) and the bike is going over what I call "stutter bumps" or cracks in the road? Stutter bumps are common on concrete surfaces where the separate concrete sections meet at a joint to form a "ridge" the bike drops over. What happens, is that as the rear tire drops over the ridge, while on the rear brake, the rear tire momentarily slows down faster than the front tire. The ABS II senses this as pending lockup, and releases brake pressure to the rear brake and you'll hear the ABS pump cycle. Again, normal funtioning.

    If that is the situation, it is totally normal for the ABS II and the bike. My 94 RS has done that since I started riding it. My RS also cycles the ABS pump randomly after I have come to a stop w/o ABS actuation. I believe it is simply a fact of the ABS control logic. To your other questions:
    Changing the brake hoses will not affect the system sensitivity.
    There is no adjustment to affect the system sensitivity.
    ABS II is not known to be overly sensitive. I've never had issue with it and it is very effective.
    It does not affect your stopping distance, as long as you are using both brakes.
    It does not affect the bike stability as it only the ABS reacting to a change in wheel speed.
    There is no "bypass" other than disabling the entire ABS II, for which you gain nothing. Why is the cycling action of the ABS bothering you, since it is actually working as intended.

    I suggest you monitor when the reaction happens so you become more familiar to when it is likely. If it is happening on stutter bumps, at least then you'll learn to expect it and it won't be so disturbing. This is certainly no reasom to "bypass" the system. The ABS II system is very effective and it will save your can when the time comes you need it. In fact, I suggest regularly going out to practice high effort braking skills, and get familiar with how the ABS engages and reacts. I do this every season.
    Last edited by ANDYVH; 12-03-2012 at 11:02 PM.

  6. #6
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    I appreciate the feedback.

    Here is a little more to go on:

    I am using the EBC HH front and rear pads.

    I am not touching the rear brake at all, just progressively pulling the lever toward the bar in what I consider a medium to medium hard deceleration; all in straight line upright smooth road conditions. The ABS kicks in and releases the brakes.

    The brake discs were replaced on this bike all the way around. New BMW RS rotors up front and a nearly new rear disc off a K12GT gen 1.

    BMW ABS systems are not unfamiliar to me with the exception of ABS II. The condition is impacting stopping distance.

    The guys on BMWST suggested bleeding the unit and to check the ABS sensor gaps; something I'll get to later this week.

  7. #7
    Day Dreaming ... happy wanderer's Avatar
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    Quote Originally Posted by limecreek View Post
    I appreciate the feedback.

    Here is a little more to go on:

    I am using the EBC HH front and rear pads.

    I am not touching the rear brake at all, just progressively pulling the lever toward the bar in what I consider a medium to medium hard deceleration; all in straight line upright smooth road conditions. The ABS kicks in and releases the brakes.

    The brake discs were replaced on this bike all the way around. New BMW RS rotors up front and a nearly new rear disc off a K12GT gen 1.

    BMW ABS systems are not unfamiliar to me with the exception of ABS II. The condition is impacting stopping distance.

    The guys on BMWST suggested bleeding the unit and to check the ABS sensor gaps; something I'll get to later this week.
    Since you replaced the rotors I'm betting you're going to find the sensor gaps are way off and this is causing your problem. The ABS II system is not over sensitive but those gaps do need to be just right for it to work properly.

    Double check the correct gap for your bike. Most bikes have a sticker on the shaft tunnel stating the correct ABS gap. There were two different gaps for the ABS II bikes if memory serves.
    MJM - BeeCeeBeemers Motorcycle Club Vancouver B.C.
    '81 R80G/S, '82 R100RS, '00 R1100RT

  8. #8
    Registered User m_stock10506's Avatar
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    If the gap was that far off, wouldn't the ABS-II system throw a diagnostic fault code?
    Michael Stock, Trinity, NC
    R1100RT, R100, R60/6

  9. #9
    Nickname: Droid
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    Not if it is getting some signal from the speed sensors. The sensors are nothing but coils that generate a voltage output as the toothed wheel passes by. If the sensor is too far back the signal strength may be weaker, but still there.

    I agree, check the sensor gap. An easy way to adjust it is to loosen the clamp bolt just enough to push the sensor in till it just touches the tone wheel. Then rotate the wheel assembly and the wheel runout will push the sensor back to produce the running clearance gap. Then wiggle a 0.015" feeler gage in and tighten the bolt.

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