ABS engagement question

[aterry1067]

Hey all,

 

I have been thinking about the abs system on my 2000 R 1100 RT. During a hard brake maneuver, will the ABS take over both brakes, or just the out-of-tolerance wheel? What I am thinking as I pose the question, the front tire obviously has a lot more traction than the back tire under hard braking. That said, if during a hard brake maneuver, would I be better off not touching the rear brake (if I'm already close to ABS engagement)? If I engage the rear brake enough that it engages the ABS, would the ABS also release pressure on the front brake, even though it has a much larger usable portion of the "traction pie" left at it's disposal?

 

I hope this makes sense.

 

Thanks in advance for any and all responses.

 

[russell_bynum]

With ABS-II on your R1100RT, ABS will kick in on just the out-of-tolerance wheel.

[BevBeng]

Here's a nice comparison on bikes with and without ABS in the wet.

Nice front wheel shot in lock up with and without ABS around 1:31.

[Michaelr11]

With the 1100 ABS-II system, don't over think it; just use all of the brakes you can on both wheels.

[dirtrider]

Afternoon aterry1067

 

Good question and it shows you are thinking outside the box.

 

On your 2000RT it has an ABS-2 brake system and that is a fairly antique somewhat slow clutch/ piston type ABS system.

 

For normal (non ABS) braking your front and rear operate as an independent stand alone systems. Under normal light or slippery road ABS action, again mostly front/rear stand alone.

 

BUT- (always a but) there are times that the rear being in ABS mode can effect the front braking. Even though your ABS system is kind of long in the tooth now is was a bit ahead of other motorcycle ABS systems of it’s time. It has a built in algorithm that prevents excess rear wheel lift (stoppies if you will). The system monitors rear wheel slippage vs the front as well as against built in decel curves and if it sees impending rear wheel lift it will release some front brake to counter that rear wheel lift. Problem is, it can’t always discern rear wheel lift from momentary lock up due to sliding over tar strips, or jumping over square edged bumps, or locking while bouncing over chatter bumps, or momentarily locking over a gap in the road surface. - So there are times when the rear lockup can effect front braking, therefore effect front braking force & overall stopping distance.

 

If your bike was a short wheel base sport bike then not using the rear brake probably wouldn’t make much difference. Seeing as the length and balance of your BMW RT allows a pretty good usage of the rear brake to decrease stopping distance you really need to use it if possible. The secret is to use as much rear as possible but keep it from locking in a manner that your ABS system thinks the rear wheel has lifted off the road. This isn’t difficult on a slippery road surface as the rear and front are more than likely seeing some slippage or impending lock up at an acceptable level. It is more difficult on a dry high traction road surface with square edged bumps or cross road tar strips. In this case you might get a better stopping distance by letting off some rear brake once the bikes weight transfers to the front wheel.

 

It’s a difficult thing to guess at as not all rear wheel traction changes trigger the anti-lift control.

 

You might take what I posted above then go out on different road surfaces and see how much rear brake can be used for how long before you get a nano second (unexpected) front wheel brake release. You will know it when it happens as the bike will take a small learch (jump) forward as the front brake momentarily releases then re-applies.

 

 

 

 

 

 

[russell_bynum]

It has a built in algorithm that prevents excess rear wheel lift (stoppies if you will). The system monitors rear wheel slippage vs the front as well as against built in decel curves and if it sees impending rear wheel lift it will release some front brake to counter that rear wheel lift.

 

Do you have any sources to back that statement up?

 

That has never been my experience.

 

That was a well-reported "feature" of the early servo-ABS systems that were on the first few years of the R1150RT, but this is the first I've heard anyone reporting it with ABS-2.

[russell_bynum]

In this case you might get a better stopping distance by letting off some rear brake once the bikes weight transfers to the front wheel.

 

That is the case on any motorcycle regardless of brake system. The more front brake you apply, the more weight transfers forward and the less traction you have available on the rear. Eventually you'll get to the point where the rear wheel is lifting off the ground...in which case you'll be using no rear brake at all.

 

[dirtrider]

Evening Russell

 

You ask:

 

"Do you have any sources to back that statement up?"---- Yes, I have a couple of sources including info from BMWNA.

 

"That has never been my experience." – I can’t’ help you there, I you have owned an 1100RT with the ABS-2 and braked hard on rough roads or square edged bumps you should have felt the anti lift kick in.

 

"That was a well-reported "feature" of the early servo-ABS systems that were on the first few years of the R1150RT, but this is the first I've heard anyone reporting it with ABS-2." – If you want to follow up give Anton a call. I think he published some data at one time of the anti lift operation in the ABS-2 systems

[russell_bynum]

Evening Russell

 

You ask:

 

"Do you have any sources to back that statement up?"---- Yes, I have a couple of sources including info from BMWNA.

 

"That has never been my experience." – I can’t’ help you there, I you have owned an 1100RT with the ABS-2 and braked hard on rough roads or square edged bumps you should have felt the anti lift kick in.

 

"That was a well-reported "feature" of the early servo-ABS systems that were on the first few years of the R1150RT, but this is the first I've heard anyone reporting it with ABS-2." – If you want to follow up give Anton a call. I think he published some data at one time of the anti lift operation in the ABS-2 systems

 

I'd be interested to see that info. I put 70K miles on a 2000 R1100RT with quite a bit of time spent playing with the brakes. I've had the rear wheel so light that it was skittering from side to side...with occasional hops an inch or two into the air. If actually having the rear wheel lift isn't enough to cause the anti-lift to kick in, then I'm not sure what is.

[dirtrider]

Evening Again Russell

 

 

The info I have was given to me with a promise from me of not posting or releasing it to the public. If you don’t believe me (and it sounds like you don’t) then I can’t help you. Again I suggest you call Anton or do some research on your own as the ABS-2 anti lift ability has been well mentioned in a few motorcycle road tests as well as some technical articles when the ABS-2 system first appeared.

 

Now, just because it (the ABS-2) has the anti-lift algorithm that doesn’t mean you can’t get some rear wheel lift. It won’t lift high and it won’t lift for very far. My latest 1200 hexhead is light years ahead of the old ABS-2 response speed and read ahead ability and I can get some rear wheel lift on that if I try hard enough but I sure can’t do a tail high stoppie with it.

 

I’ll bet before the thread is done you will hear from some riders in states with rough roads or frost heaves in the roads that they have had their ABS-2 systems take a (heart pounding) forward jump when stopping hard using a lot of rear brake. Pretty common complaint when the ABS-2 first came out.

 

[DiggerJim]

The info I have was given to me with a promise from me of not posting or releasing it to the public.

Reminds me of Double-Top-Secret Probation...trust me

 

My latest 1200 hexhead is light years ahead of the old ABS-2 response speed and read ahead ability and I can get some rear wheel lift on that if I try hard enough but I sure can’t do a tail high stoppie with it.

Probably don't want to watch this about 40 seconds in...

 

[Indy Dave]

Probably don't want to watch this about 40 seconds in...

 

That's a modified bike, the rules don't apply.

[russell_bynum]

Evening Again Russell

 

 

The info I have was given to me with a promise from me of not posting or releasing it to the public. If you don’t believe me (and it sounds like you don’t) then I can’t help you. Again I suggest you call Anton or do some research on your own as the ABS-2 anti lift ability has been well mentioned in a few motorcycle road tests as well as some technical articles when the ABS-2 system first appeared.

 

Now, just because it (the ABS-2) has the anti-lift algorithm that doesn’t mean you can’t get some rear wheel lift. It won’t lift high and it won’t lift for very far. My latest 1200 hexhead is light years ahead of the old ABS-2 response speed and read ahead ability and I can get some rear wheel lift on that if I try hard enough but I sure can’t do a tail high stoppie with it.

 

I’ll bet before the thread is done you will hear from some riders in states with rough roads or frost heaves in the roads that they have had their ABS-2 systems take a (heart pounding) forward jump when stopping hard using a lot of rear brake. Pretty common complaint when the ABS-2 first came out.

 

It is entirely possible that I'm wrong. But...I've been here for the better part of 10 years and we've had a gazillion discussions about what the various ABS setups do (and don't do). Never once have I heard anyone claim that ABS-2 has anti-stoppie features.

 

On the other hand, that was a very common topic of discussion with the power brakes on the R1150RT when it first came out. It was commonly known around here as the "ice patch= effect" and is exactly as you have described.

[aterry1067]

Cool. Thanks for all the replies. I'll test things out and see what feels best, and continue using both brakes to reinforce the habit. I certainly appreciate all input. Thanks again guys. Great board!

 

[ShovelStrokeEd]

In support of Russell,

I had 2 bikes so equipped. A '94 R1100S and a 2000 R1100 RT. Neither one would do the anti-stoppie thing. My '04 GS Adventure (whizzy brakes) would scare the hell out of me when braking hard over stutter bumps.

[russell_bynum]

In support of Russell,

I had 2 bikes so equipped. A '94 R1100S and a 2000 R1100 RT. Neither one would do the anti-stoppie thing.

 

That's probably because you haven't ridden on any rough roads.

 

 

[motorman587]

Can a RT, even with out the supposed anti-stoppie or abs, do a stoppie?? Isn't the RT just designed not to that??? I mean it is not a sport motorcycle..........

[dirtrider]

Probably don't want to watch this about 40 seconds in...

 

Afternoon Jim

 

Interesting video, he must have the ABS disconnected as I see the rear wheel totally locked up and smoke coming from the rear tire. OR, maybe a new type of ABS that doesn’t really prevent wheel locking. Kind of like standard brakes only with all the extra weight and complexity added in.

 

[dirtrider]

Can a RT, even with out the supposed anti-stoppie or abs, do a stoppie?? Isn't the RT just designed not to that??? I mean it is not a sport motorcycle..........

 

Afternoon Motorman587

 

You must have missed this---

 

 

[russell_bynum]

Can a RT, even with out the supposed anti-stoppie or abs, do a stoppie?? Isn't the RT just designed not to that??? I mean it is not a sport motorcycle..........

 

Afternoon Motorman587

 

You must have missed this---

 

 

Yup. Goy does that stuff on the big LT as well. And somewhere I've seen footage of similar shenanegains on a full-dress Harley.

[motorman587]

Can a RT, even with out the supposed anti-stoppie or abs, do a stoppie?? Isn't the RT just designed not to that??? I mean it is not a sport motorcycle..........

 

Afternoon Motorman587

 

You must have missed this---

 

 

Sorry have a job and kids...........lol