Rear brake pedal vibration under firm braking - BMW F800 Riders Forum & Registry



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  1. #1
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    2017 F800GT which I've had a couple of months, had 3,000 miles on it when I bought it.

    If I put firm pressure on the rear brake pedal during a stop, I often get a rapid vibration or pulsing sensation through the pedal. This is firm braking, not stomping on the pedal. I would have thought nowhere near hard enough to trigger the ABS, although it sort of feels a bit like ABS pulses. Only happens on rear brake, not front. Can't feel anything out-of-whack with either brake under lighter braking.

    Any ideas?

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  3. #2
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    I find the rear ABS will come on quite easily when braking firmly. The weight of the machine is thrown onto the front tyre and consequently there is very little weight on the rear. Traction at the rear reduces, the wheel slows more than the front and the ABS kicks in.
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    I noticed the same thing with my first BMW boxer that had ABS. Like you, only when braking using just the rear brake. However, I do not notice this feature with my RS and my F650GS does not have ABS. Both my Zero and my KTM also have ABS and those bikes do not pulsate when braking, but frankly I never brake very hard using the rear brake anymore. Mostly, I just use the front brake and just cover the rear brake pedal should I need it.
    Richard - Current bikes: 2016 BMW R1200RS, 2018 16.6 kWh Zero S, 2011 Royal Enfield Bullet 500 Classic, 2009 BMW F650GS, 2020 KTM 390 Duke, 2002 Yamaha FZ1 (FZS1000N) and a 1978 Honda Kick 'N Go Senior. 

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    Biscuits. This is something that irritates me a little. Really the only thing I don't like on an otherwise great bike. I tend to drag the rear brake when pushing on in the twisties to help steer. Something I developed from years on a BMW airhead, shaft drive. As Ian has said, the ABS is a bit over sensitive at the rear. While I consider ABS a great safety feature, it's a pity we don't have the option to turn it off. Just to see how intrusive our ABS is, try riding on a twisty gravel road at speed!

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    Quote Originally Posted by Redned View Post
    Biscuits. This is something that irritates me a little. Really the only thing I don't like on an otherwise great bike. I tend to drag the rear brake when pushing on in the twisties to help steer. Something I developed from years on a BMW airhead, shaft drive. As Ian has said, the ABS is a bit over sensitive at the rear. While I consider ABS a great safety feature, it's a pity we don't have the option to turn it off. Just to see how intrusive our ABS is, try riding on a twisty gravel road at speed!
    My KTM Duke allows the rider to turn off the ABS on the rear brake. I think BMW also allows the ABS to be turned off on their R12GS models. So they could do it on their F800 models if they wanted too.
    Richard - Current bikes: 2016 BMW R1200RS, 2018 16.6 kWh Zero S, 2011 Royal Enfield Bullet 500 Classic, 2009 BMW F650GS, 2020 KTM 390 Duke, 2002 Yamaha FZ1 (FZS1000N) and a 1978 Honda Kick 'N Go Senior. 

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    According to the manual, the ABS system will turn itself off if a fault is detected. "Driving on the rear wheel (wheelie) for a longer period". Another method mentioned is "Rear wheel spinning in place with front brake engaged (burn out)". Doesn't seem like it would be all that hard to turn it off when you want

    There are a few more boring methods mentioned too. Seriously though, what I've heard many people did with older GS's was to use a momentary switch on either the front or rear wheel speed sensor to disrupt the signal while riding. The ABS will disable until you turn off and restart the engine. I 'think' it's the rear you want, pretty sure the front will throw a speedo error too.

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    rcb78. I had wondered if disabling the rear sensor would make the ABS system throw an "error" and switch itself off. Although I had pondered it, I've not been game enough to try it. I'm not sure I like messing about with the braking system. However logic says disabling the AbS shouldn't have any effect. I wasn't aware that the GS mob had tried it.

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    I never had that feeling with mine, didn't use the rear brake a lot except when braking very hard and in wet conditions. IMO the rear brake was anemic compared to the front. Often wondered if the pads were glazed or had something on them but never worried about it that much.

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    I bought my bike used with 8,000 miles on it, and the rear brake had a slight pulsing anytime I used the rear brake. The pulsing was not a "pedal pulse" - but you could feel the braking was harder at one particular portion of the rotor, and the pulsing was related to the wheel rotation.....the pulse slowed down as the wheel rotation slowed down. I had initially though the rear disc was warped - but when I checked it with a dial indicator the disc was straight. The dealer I bought it from had a huge inventory and all used bikes got pushed outside during business hours....rain or shine - I suspect the exposure to the environment and lack of riding may have caused the problem through some kind of corrosion onto the disc (however nothing was visibly evident).

    I tried cleaning the disc to resolve the problem - but nothing helped. Eventually the issue went away on it's own.......riding evidently cleaned the disc of whatever was causing the problem.

    The only time I ever feel the ABS work - is when I am braking and the rear wheel jumps over a pothole or other pavement defect that causes the rear tire to unload the weight or lose contact with the pavement. The pulsing stops soon after the tire gains contact wit the pavement. Up to this point I have never "over-braked" with the rear wheel during hard stops.......the ABS has never needed to kick in under normal braking on smooth road surfaces.

    Biscuits - Can you tell if the pulsing frequency in your brake pedal actually the ABS functioning......or related to the rotation of the disc?

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    Sounds like the ABS kicking in. If it was a warped disc i think you'd feel it under light braking too. It may be the ABS pick up ring needs cleaning, if there's too much dirt on it they can pick up those as a gap and think the wheel is under rotating vs the front, and is about to lock up.
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    Yup, it is the ABS. It gives you an idea of how little braking effectiveness you get from the rear wheel. I use my rear brake only in places where slow maneuvering is required and where hitting the front brake will put me on the ground quicker than I can realize what happened.

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    Quote Originally Posted by Thumpin View Post
    Biscuits - Can you tell if the pulsing frequency in your brake pedal actually the ABS functioning......or related to the rotation of the disc?
    I'd say the vibration would be a lot more than once per wheel rotation.

    I'll see if I can find a clear, straight, dry section of road and investigate some more.

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    Quote Originally Posted by Thumpin View Post
    I bought my bike used with 8,000 miles on it, and the rear brake had a slight pulsing anytime I used the rear brake. The pulsing was not a "pedal pulse" - but you could feel the braking was harder at one particular portion of the rotor, and the pulsing was related to the wheel rotation.....the pulse slowed down as the wheel rotation slowed down. I had initially though the rear disc was warped - but when I checked it with a dial indicator the disc was straight. The dealer I bought it from had a huge inventory and all used bikes got pushed outside during business hours....rain or shine - I suspect the exposure to the environment and lack of riding may have caused the problem through some kind of corrosion onto the disc (however nothing was visibly evident).

    I tried cleaning the disc to resolve the problem - but nothing helped. Eventually the issue went away on it's own.......riding evidently cleaned the disc of whatever was causing the problem.

    The only time I ever feel the ABS work - is when I am braking and the rear wheel jumps over a pothole or other pavement defect that causes the rear tire to unload the weight or lose contact with the pavement. The pulsing stops soon after the tire gains contact wit the pavement. Up to this point I have never "over-braked" with the rear wheel during hard stops.......the ABS has never needed to kick in under normal braking on smooth road surfaces.

    Biscuits - Can you tell if the pulsing frequency in your brake pedal actually the ABS functioning......or related to the rotation of the disc?
    I had that same pulse and assumed it was a warped disc as well. Mostly noticeable at very slow speed. Just recently had the rear hub bearings commit suicide, and after the hub was replaced the pulse disappeared completely.

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    Quote Originally Posted by Biscuits View Post
    2017 F800GT which I've had a couple of months, had 3,000 miles on it when I bought it.

    If I put firm pressure on the rear brake pedal during a stop, I often get a rapid vibration or pulsing sensation through the pedal. This is firm braking, not stomping on the pedal. I would have thought nowhere near hard enough to trigger the ABS, although it sort of feels a bit like ABS pulses. Only happens on rear brake, not front. Can't feel anything out-of-whack with either brake under lighter braking.

    Mine is a 2016 model and I have noticed the same annoying issue. Interestingly I don't recall noticing anything prior to the first time I really did have to slam on the breaks and the ABS pulse was quite strong. Since then I get a milder form of the ABS pulse whenever I put anything more than slight pressure on the pedal. It cuts in way too quickly!

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    Quote Originally Posted by Biscuits View Post
    2017 F800GT which I've had a couple of months, had 3,000 miles on it when I bought it.

    If I put firm pressure on the rear brake pedal during a stop, I often get a rapid vibration or pulsing sensation through the pedal. This is firm braking, not stomping on the pedal. I would have thought nowhere near hard enough to trigger the ABS, although it sort of feels a bit like ABS pulses. Only happens on rear brake, not front. Can't feel anything out-of-whack with either brake under lighter braking.

    Any ideas?
    I found this same symptom on a K1200LT. Turns out the owner had the rear rotor turned in a brake lathe, and it was way out of true. As much as 25 thousandths difference in the thickness around the disc. You might check your rear disc for distortion or warpage.

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