ABS vs "stoppie"

[maxscycle]

Folks
My friend has a 06r12rt and he has the ability to do a stoppie. I have never tried to do one on my 06r12gs. he has had it to the dealer and they said everything was working fine, brake/abs wise.
It puzzles me. How can the abs work "fine" and yet be able to raise the rear tire?
Thanks
Max

[rbertalotto]

If it's working correctly, he should not be able to lock up the front wheel, unless his bike is balanced in such a way that simple deceleration of the front wheel lifts the back.......I think not!

I can't do stopies on my Rockster.........or on my DL-650........or on my VFR....

check out this video


http://youtube.com/watch?v=3d6iu-1WFxw

[Andy VH]

The degree of rear wheel lift is dependent on the braking forace applied and the reaction time of the ABS computer once it senses the rear wheel has slowed significantly more than the front.

Note, the rear wheel, if airborne, does not have to lock or stop spinning for the ABS Stoppie over-ride to engage. There are many variables in the whole stopping sequence that influence how much the anti-stoppie logic will control rear wheel lift.

When you say "stoppie" about his 06R12RT, is it over anything more than two bike lengths? If just two bikes lengths that is probably normal within the controller logic. If he can do a sustained stoppie as long as he wants, then there is something different in the ABS system on his bike that allows that to happen versus your GS.

[BigAdv]

"Even under severe braking, a high level of tyre grip can mean that the front wheel does not lock up untill very late, if at all. Consequently, ABS does not intervene until very late, if at all. Under these circumstances the rear wheel can lift off the ground...."

Quoted from the riders manual.

Dont forget that this is a two channel system, it will only prevent the wheel that is at the threshold from locking, so even if the rear wheel is in a locked condition, it will not modulate the front till it is locking. Stoppies are more a function of balance and control than braking.

Earl

[Andy VH]

Yes it is a two-channel system, as are all motorcycle ABS systems. But the difference is the linked brakes/ABS system on the Hexheads. If the I-ABS-II system senses rear wheel lock, or wheel speed significantly lower than front wheel speed (both which the system might interpret as a stoppie event), it will release brake pressure on the FRONT brake to maintain bike stability and bring the rear wheel down to the surface.

That momentary front brake release will cause the bike to shoot forward, unbraked, for some fraction of a second. Some riders of F800s have taken great issue with this, while practically none of the LT riders have even mentioned it. Even though F800 and LT use two different ABS systems, they both have the anti-stoppie logic in the controller.

I'd like to see someone do a stoppie on an LT!

[charleshickman]

A month or so ago I was travelling at approx. 60 mph on dry asphalt when a pickup coming the opposite direction turned left in front of me. It's the closest I've ever come to a major accident on a bike.

I applied as much force to both brakes as possible. The rear did a minor, easily controlled, fishtail immediately after I applied maximum braking force. While it was not at the top of my mental processes at the time, upon reflection I decided that I had done a 1 or 2 second stoppie.

I missed the truck, the bike and ABS system performed flawlessly and I think that the ABS paid for itself on that one incident. I've got an '06, and so am burdened with the servo assist, but no longer have standing to complain about it.

[gulfcoastbeemer]

I'm zipping along in city traffic on my ABS equipped, '07 R1200RT: my lane is doing maybe 35 mph, and the lane to the right is completely backed up -- at a standstill. You know what comes next...

Without looking, a car that is stopped in the righthand lane decides to blindly swing into my lane -- RIGHT INTO MY PATH. Uh oh...

Nowhere to swerve to: oncoming traffic zooming toward me to my left; a wall of stopped cars to my right, except for the jerk that is now pulling out, maybe two car-lengths, in front of me.

Instincts take over: I hang on, clamp my legs on the tank, keep the bike straight and squeeze the front brake lever -- hard, then harder, then as hard as I can.

The bike stops REALLY fast -- so fast that the rear wheel lifts at least a foot off the ground for maybe 15 feet. While I'm in mid-"stoppie", the guy in the car realizes his mistake and hit the gas. Thankfully, I didn't have to come to a complete stop or I might have lost it, and dropped the bike.

It was over in two or three seconds. But, those seconds seemed an eternity. I hadn't planned on learning how to do a "stoppie" in traffic, but I think it was quite a success, even if I say so myself.

As far as I'm concerned you can lift the rear-wheel off the ground without locking the front-wheel.

[Andy VH]

Yes, certainly you can do a stoppie without locking the front wheel/brake. In fact, that is how a stoppie is done, lifting the rear wheel with the bike in motion wihtout loosing control of the front brake.

In fact, on a bike without ABS, my guess is if during a stoppie you do lock the front tire (and assuming you don't immediately dump the bike) the stoppie will quit and the rear tire will come back down. Because now the front tire has lost the braking effort which caused the rear of the bike to pivot up around the front wheel axle.

Up until recently, if your bike had ABS or not, and if you had the skills to do it, any normal bike could be made to do a stoppie as long as the front wheel is kept from locking. Even my 94 R1100RSA could do it. What has changed with the updated ABS-8M (on the F800) and the I-ABS-II (on the R and K bikes) is the contorl logic BMW has included that actually restricts or eliminates the option to do stoppies.