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ABS spazzing out over bumps

Discussion in 'Technical and Troubleshooting Torque' started by Loz, Jun 11, 2015.

  1. Anyone else run into this?

    I've had ABS do its nana on two different bikes on the same piece of road, and leave me with effectively no brakes. I prefer having brakes.

    Situation is thus: a short wide road that I tend to pop a whoolie on of a morning, with a traffic light at the end so I need to pull up fairly briskly. There's three big tree roots under the road that act like speed bumps in the braking zone, so you have to put the front down, settle it, brake hard, release to give the suspension some travel to deal with each bump, then brake hard again after each one. It's a bit of a mental exercise I like to do in brake and suspension control. It's no drama on a bike with no ABS.

    But on the Triumph, and a few weeks ago the KTM, it's making the ABS go bananas. Something about this situation triggers it to think it's lost traction or some such, and it just releases the brake. The lever is useless, I've got bugger all stopping power. I don't much like it. It's making me think I should turn ABS off by default, when ABS was actually one of the reasons I went for this bike. Your thoughts?
  2. It's happening due to the wheel slipping because of the bouncing action of the bumps. Turn it off for that stretch, or go less aggressive, perhaps.
  3. I'd turn off the ABS...until someone can offer a work around when ABS on. Given the surprise that you can suddenly get when you come hit some of our sad looking roads I wouldn't want to be minus my brakes then...
    • Agree Agree x 1
  4. Trouble is, most bikes make you turn it off every time you get on the bike. What a PITA.
  5. I don't have ABS so can't comment. But must be something fundamental to the working's of ABS for it to happen on two different bikes under the same conditions though.

    Some people go for a run, or do stretches and yoga in the morning. Loz pops a wheel and brakes hard. Nice routine, i like that.
    • Agree Agree x 2
  6. Maybe you got the wrong extra... Announce Bump System. :rolleyes: Sorry works a real grind today.
  7. Pop your morning wheelie elsewhere....middle of the Monash maybe? :wtf:
  8. Yeah I'm not worried about this specific spot, more that the ABS might catch me out one day when I'm in the hills riding hard.
    • Agree Agree x 1
  9. I'd be inclined to take it to the hills for a bit longer than usual, ease into it and build up to the point where I could trigger the ABS. Get a good idea of what it does, and when. I'm with you LozLoz, I don't want the electrics kicking in unexpectedly when the brakes are all that's keeping me from launching into a valley.

    Edit: just occurred to me, is there any chance the tyre brakes traction momentarily as it crests each root? Not massively, just a little hop on the back side of the bump - may be enough to trick the wheel sensors that you've locked it up?

    It's a family forum so I won't go into what I stretch in the morning.
    • Like Like x 1
  10. 'tis a worry. Bumps may be one of the reasons you are suddenly in a pickle. I suppose it's the unloading of the front wheel, less weight and the wheel starts to lose traction. How close together are the tree roots? - too slow typing hyperspex beat me to it.
    • Agree Agree x 1
  11. #11 robsalvv, Jun 11, 2015
    Last edited: Jun 11, 2015
    *whistles aimlessly* (Ok Lozzo... you know you and I have history over bike ABS... but this isn't the usual rant. lol. In fact, the ABS is doing exactly what it's been designed to do)

    Ok, look, as I keep saying to anyone who'll listen, stay within the programming parameters of the ABS and understand its implementation and you wont even know its there and it wont interfere with your riding. There's a reason that sports riders have resisted ABS for so long - it's not just about being technophobe curmudgeons. The top flight ABS's are pretty bloody good now as a result of all this complaining.

    On low traction surfaces, all ABS's do their jobs brilliantly - it brilliantly stops the tyres from locking... which means, a bike tends to "run on" in low traction conditions because the tyres lock so easily. What's a poor ABS to do? It's designed to stop wheels from locking.

    Hard braking over bumps where the tyres go light is akin to low traction. When the tyre goes light, the hard braking will lock a wheel and the ABS kicks in. It doesn't know about bumps, it only knows that the wheel/s have stopped rotating or predicts that they are about to stop rotating.

    A wheel that shocks to lock under heavy braking is released under ABS and then the ABS allows the full force of the braking effort to be reapplied and the wheel shock locks again which is released under ABS and then the ABS allows the full force of the braking effort to be reapplied and the wheel shock locks again which is released under ABS... that's one reason why you must still brake properly and progressively to get the most out of ABS. A panic grab of ABS will lead to a longer braking distance than a well heeled braking effort unless it's sophisticated ABS. Super sophisticated ABS has ramp up factors programmed in to avoid this scenario and manage weight transfer. You won't get that on your mandatorily ABS'd 125cc budget PTW. But I digress.

    This is why going down a dusty dirty hill or bumpy road on a chook chaser with simple ABS is heart in mouth scenario. A dirt bike with well programmed ABS only has ABS on the front or at the very least a mode that turns it off on the rear. Dragging a locked rear wheel is a good thing down a bumpy hill, but ABS won't allow that and with every bump that causes the tyres to get air born or light resulting in a wheel lock, pow, ABS kicks in.

    And if you have one of those sophisticated ABS with angle sensors and antistoppie features then every time the REAR locks or the bike senses the rear rising, the ABS does it's EBD thing to change the braking % balance, i.e., reduces braking effort up front and you "run on".

    Checkout some Strom forums, they have guides on how to cut in a switch so you can turn the ABS off.

    ABS is good and fine. It stops wheels from locking under brakes.
    • Informative Informative x 5
    • Like Like x 2
  12. Nicely put Robsalvv.
  13. #13 ibast, Jun 11, 2015
    Last edited: Jun 12, 2015
    Makes me wonder whether you've wound up the front rebound damping too much.
    • Like Like x 2
  14. So ABS works properly when you ride it like Grandma going to the shops on a scooter...
    And ABS does NOT work properly when you're attempting to exercise full manual control of the machine...?
    Who'da thunk...

    I think I'll just stay analog.
    • Agree Agree x 4
  15. I'm with you titus.

    Sadly, we won't have a lot of choice. :-(

    The bit that really worries me, is how do you actually test of your new ABSed bike.

    Are you really gonna rush down the main straight at Eastern Creek at full revs in 5th or 6th gear, snatch the front brake lever as hard as you can, and try and make turn 1?

    No thanks, I'd really rather not.
  16. Hey LozLoz have you tried see what happens when you go over those nipply bluey or orangey hazard bobble thingos they put at intersections or at the entrances to some buildings to slow or warn traffic? Does that even make sense...anyway I just wondered how the ABS handles these...
    I posted somewhere else on NR that I was leery of ABS and I got ripped a small new one...now I am thinking I may give it a miss...
  17. Even riders have carcentric views of motorcycle ABS and very few riders have any serious working concept of bike ABS. They are not all the same.

    Having said that, the top flight sophisticated ABS is seriously good and it would take the elite of the elite to outbrake the flagship ABS's in the dry on good pavement.

    The simple ABS packages are entirely another thing. Hot tip with these packages, set up and squeeze.
    • Like Like x 1
  18. Without getting into the discussion I have only this to say:-

    Each bike is different, it is up to you to learn how it behaves and practice. As an example the first thing I did with my bike when I got it was take it to Sat practice in the wet and see how it behaved under hard breaking and panic snatching of the front. It was very different from the previous bike.

    Cheers Jeremy
  19. Yea that is shithouse
    No ABS here... wanna trade?

    I'm surprised they don't allow you to change the level of intervention like traction or wheelie control, really falls into the same bucket.

    Will come sooner or later.
  20. on non-ABS bikes, does the front skip over the bumps and skid a bit when it comes down?
    an airborne wheel with brakes applied stops pretty quickly, compared to when in contact with the road.

    the trumpy Abs is probably detecting the airborne front wheel deceleration being faster than rear, assuming wheel is still in contact with road and anticipates a lock situation.. it doesn't need to actually lock to trigger the ABS.

    it's vaguely like Torsen LSD in cars.. you need both wheels on the ground for it to work properly.
    but in this case, the bike wants the front wheel on the ground while you are braking with front wheel :D

    how is it on wet/dusty/gravel surfaces?

    if it triggers unpredictably, there is possibly a chance of air in the system, particularly if it is detecting line pressure as well as wheel speed