ASC and high side flips

[Frustrated_Diver]

This question might be in the wrong forum but it is specific to a R1200RT, a real life Hexhead. Ergo, the reason my brain, such as it is, thought this would be the correct forum. So, dear Moderator, i apologize if i committed an oops and i beg your forgiveness.

 

The Credit Union's bike that they so graciously allow me to enjoy is equipped with the Automagic Stability Control feature. If i were to lock up the rear wheel by braking too hard and then release it, do you pontificators think the ASC would do its best to prevent a high side flip? You see, i'm too chicken to try it and would much rather settle for theories and opinions.

[R4ND0M_AX3]

ASC Limits forward rotational slip (like wheel spin on slick surface).

ABS limits the opposite (aka lock).

 

 

ASC does it's job by reducing power from the engine.

ABS does it's job by reducing braking force at the brake discs.

[LuckyLeif]

Easy to confuse ABS & ASC....I think you are asking about a rear brake lock-up on a good traction surface causing the rear to fishtail, a regain of traction and a subsequent high side crash. Shouldn't happen if your ABS is functioning. ASC has no role in this as it's function is to prevent rear wheel slip from over agressive throttle application in limited traction environments.

[tallman]

Bring your bike to BRR.

Someone will volunteer.

 

"Here hold my beer and watch this..."

[ShovelStrokeEd]

ABS wont help you a damn bit in a turn if the sum of lateral and rotational traction required exceeds the total of traction available. In other words, ABS is wonderful for keeping the wheel from locking during braking but it will do nothing to prevent side slip during turning.

 

ASC acts in a similar way in that it will prevent wheelspin but will do nothing for sideways slip.

 

I would suggest you not try to test this as the results could be both expensive and painful.

[lawnchairboy]

[John Bentall]

Ed, if you read the OP's post carefully you will see that his bike is equipped with "AutomaGic" Stability Control. This is obviusly a pre-production version of BMW's new anti-high-side anti-flip-over control software.

[Ken H.]

This is obviusly a pre-production version of BMW's new anti-high-side anti-flip-over control software.

That's the good news. The bad news is that Mircosoft wrote it.

[Fugu]

The bad news is that Mircosoft wrote it.

 

If you find yourself about to high side and the AutomaGic is not intervening, just press the horn button, the right turn signal cancel, and the trip odometer reset simultaneously to re-boot.

[Frustrated_Diver]

Darn, after i posted my original question i knew that i had screwed up by not mentioning ABS. Yes, i know the difference between ABS and ASC and i also think i understand that at its core, ASC kicks in when it senses a difference in the speed of the front and real wheels as might happen on gravel. That is why i was wondering if it might just be a lifesaver in the event of a potential high side flip. In my mind and since i have not yet done a high side flip (and don't want to do one either), i envision the conditions being right to trigger the ASC software to react. The way it reacts, according to the BMW manual, is to start adjusting the engine's output and i was wondering if that would be enough to stop the flip.

[John Bentall]

BMW are VERY clear that the ASC is there to provide benefits when accelerating over loose surfaces and ice when the bike is upright. It does not react quickly (as in MotoGP quickly enough) or sensitively enough to prevent a high-side flip when cranked over in a curve.

[R4ND0M_AX3]

A highside is caused by the rear tire sliding sideways then suddenly griping. The only way to prevent this is to not slide in the first place or not suddenly regain grip after the slide has begun.

[AndyS]

This question might be in the wrong forum but it is specific to a R1200RT, a real life Hexhead. Ergo, the reason my brain, such as it is, thought this would be the correct forum. So, dear Moderator, i apologize if i committed an oops and i beg your forgiveness.

 

The Credit Union's bike that they so graciously allow me to enjoy is equipped with the Automagic Stability Control feature. If i were to lock up the rear wheel by braking too hard and then release it, do you pontificators think the ASC would do its best to prevent a high side flip? You see, i'm too chicken to try it and would much rather settle for theories and opinions.

To answer your question we need to know if you have ABS.

If you do, then you probably wouldn't lock the rear wheel anyway. And therefore if you didn't lock the wheel, then you wouldn't have a high side caused by the none resumtion of rotation!

Andy

[Ken H.]

To answer your question we need to know if you have ABS.

If you do, then you probably wouldn't lock the rear wheel anyway. And therefore if you didn't lock the wheel, then you wouldn't have a high side caused by the none resumtion of rotation!

Sorry, that is so not true. A high side is caused by a sudden increase in lateral, sideways, traction of the (usually but not always) rear wheel. ABS effects rotational speed of a wheel, not lateral movement. It is quite possible to high side a bike while in full ABS activation mode if a wheel loosed lateral traction then regains it.

[Yukon]

To answer your question we need to know if you have ABS.

If you do, then you probably wouldn't lock the rear wheel anyway. And therefore if you didn't lock the wheel, then you wouldn't have a high side caused by the none resumtion of rotation!

Sorry, that is so not true. A high side is caused by a sudden increase in lateral, sideways, traction of the (usually but not always) rear wheel. ABS effects rotational speed of a wheel, not lateral movement. It is quite possible to high side a bike while in full ABS activation mode if a wheel loosed lateral traction then regains it.

 

Me thinks that in order to lose traction in full ABS activation mode, you would be much more prone to low side, no? Wouldn't it be necessary to lean the bike over to the point of losing traction? I guess if you scraped the cylinder head leveraging the rear tire off the ground and then bounced back more upright a real good high side could be performed.

[AndyS]

To answer your question we need to know if you have ABS.

If you do, then you probably wouldn't lock the rear wheel anyway. And therefore if you didn't lock the wheel, then you wouldn't have a high side caused by the none resumtion of rotation!

Sorry, that is so not true. A high side is caused by a sudden increase in lateral, sideways, traction of the (usually but not always) rear wheel. ABS effects rotational speed of a wheel, not lateral movement. It is quite possible to high side a bike while in full ABS activation mode if a wheel loosed lateral traction then regains it.

Ken, I think you missed my point. It wouldn't be the ABS or traction control whch would cause or hinder a high side. I was suggesting that if you had a non ABS bike and had (say) the let the back wheel [or worse] front wheel lock up briefly in a bend then (and in the case of a front wheel lock up were remarkably lucky and had the time or ability) let off, traction might be recovered, but if it were with sufficient violence, then in that case a high side may possibly occur. However if you were riding an ABS equiped bike, then the likely hood of you locking the wheel to the same degree would be greatly reduced, and therefore all the above becomes much more hyperthetical!!!!!

Andy

[Ken H.]

Me thinks that in order to lose traction in full ABS activation mode, you would be much more prone to low side, no?

Oh I agree a low side is more likely, it always is. My point was that a high side is still possible while in ABS activation mode.

 

If the bike is in a low traction situation, which when the ABS is activated while leaned over in a curve, and almost by definition if the ABS is engaged you are in a low traction situation, and the wheel is sliding laterally, then the situation changes such that the available traction suddenly goes up, you get out of the sand or whatever, the bike will definitely stand up. And if the stand up is violent enough, you will high side over it. ABS or no ABS. ASC or no ASC. Neither technology is capable of overcoming physics.

[Yukon]

Me thinks that in order to lose traction in full ABS activation mode, you would be much more prone to low side, no?

Oh I agree a low side is more likely, it always is. My point was that a high side is still possible while in ABS activation mode.

 

If the bike is in a low traction situation, which when the ABS is activated while leaned over in a curve, and almost by definition if the ABS is engaged you are in a low traction situation, and the wheel is sliding laterally, then the situation changes such that the available traction suddenly goes up, you get out of the sand or whatever, the bike will definitely stand up. And if the stand up is violent enough, you will high side over it. ABS or no ABS. ASC or no ASC. Neither technology is capable of overcoming physics.

 

I see your point.

[Christian_rider]

You all seem to be having fun with this thread. I am not trying to hijack the thread but simply add another question to it. I have not had an ASC bike yet but am curious. If you are going over a bump or say railroad tracks with too much throttle and the rear tire spins, how long before the ASC stops, giving normal throttle responses again?

[Robus]

Could the ABS actually trigger a high side? I was taught that if you ever feel the rear wheel begin to slide, you step on the brake pedal and hold it down for dear life. What happens if the ABS decides to kick in at that point?

[ducatiparts.110mb]

I was taught that if you ever feel the rear wheel begin to slide, you step on the brake pedal and hold it down for dear life

 

Why? If you start to loose traction you surely want to regain it - and that is just what the ABS will do for you.

 

As for all this talk of highsiding, I can't think of a more docile bike than my RT and anyone who can powerslide it should get a medal.

 

Mark

[motoguy128]

or say railroad tracks with too much throttle and the rear tire spins, how long before the ASC stops, giving normal throttle responses again?

 

The moment the front wheel speed once again equals the front wheel speed. I've found ASC is less intrusive than traction and stability control on my SUV.

 

I think the easiest place to test ACS and see how it behaves is on a gravel road.

[motoguy128]

Could the ABS actually trigger a high side? I was taught that if you ever feel the rear wheel begin to slide, you step on the brake pedal and hold it down for dear life. What happens if the ABS decides to kick in at that point?

 

Who taught you that? The correct response to a rear wheel spin in a straight line or while cornering is to very , very slightly reduce throttle. At some point the bike will accelerate enough that that without adding more throttle it will regain traction. Applying brake I think would upset the bike's balance and cause a high side.

 

Specific to the question, the ABS cannot detect if the rear wheel is sliding laterally and it does not care if the wheel its' acting on is going faster than the other. IT only reacts if the wheel is going slower than in reference to the other.

[Robus]

A highside happens when the rear wheel regains traction while sliding.

[TedG]

A highside happens when the rear wheel regains traction too abruptly while sliding.

 

Fixed it.

 

Motoguy 128 is correct...slightly and gently rolling off the throttle allows the rear tire to regain traction without one of those "this is gonna hurt" moments. At least that's what works for me.

[Don_Eilenberger]

Could the ABS actually trigger a high side? I was taught that if you ever feel the rear wheel begin to slide, you step on the brake pedal and hold it down for dear life. What happens if the ABS decides to kick in at that point?

Who taught you that?

I somehow think he slightly misunderstood what the MSF teaches in the Experienced Rider course. They teach that if BRAKING and the rear wheel locks up (which means it has to be sliding) - keep it locked up so it doesn't hook up suddenly and high-side you.

 

That doesn't apply with ABS equipped bikes since the rear wheel can't lock up - and the MSF instructors usually recognize that most BMWs aren't gonna complete that exercise.