ABS speed Question?

Good evening. I had a interesting thing happening during the FART event with my ABS on my 2018 R1200RT-LC.

Does anyone know at what speed the ABS stops working? Or other wise said how fast (what speed?) do you have to be moving for the ABS to start working?

So what is the minimum speed for ABS to activate?

It's something like 4-5 mph.

Good evening. I had a interesting thing happening during the FART event with my ABS on my 2018 R1200RT-LC.

So Bernie, spill the beans - what did happen?

Yes Andy, of course I can try to explain what happened.

Riding around in damp conditions on tiny back roads, littered with dirt, stones, leaves, branches and acorns. During a down hill right hand corner, which tightened up a little more then I expected, I down shifted into first gear, while I already had the front and rear brakes activated. The rear wheel locked up and started sliding. No pulsing from the ABS, no warning lights on the dash board. So I released the rear brake to get the wheel rotating again and finished the curve. The same thing happened a few curves later. Both times it was in right hand and down hill tight curves, with lots of debris. I don't think the speed dropped below 10 mph, and I did try to release the clutch gently, to prevent wheel lockup.

When I got to a flat section, I pulled over to check if there was anything wrong with the tire or rear drive. Nothing out of the ordinary.

The bike is a 2018 BMW R1200RT-LC. The bike was sold to me fully loaded, with all options available from the factory. Most of these features don't work the way you would expect them to and the dealer ship has stopped returning phone calls about this pile of junk. But the radio works great!.

Oh by the way a older 2011 GS followed me on this same road, without any issues. And yes he is a much better rider then I ever will be.

Also I don't think there was oil on the road.

The tires mounted on the bike are Metzler Z-8, inflated to factory specs. And the motor oil is, oh never mind. LOL

Edit or forgotten to mention:

Just to add something to this story, my old 2007 R1200RT, never did anything like that while riding around in similar conditions at the same speed on the same roads in over 188,700 miles. And the same tires would last 3,000 miles longer.

This new technologies from BMW are not working and things like anti-hopping clutches are more fantasies than reality, Plus I think there is a big software problem.

Interesting as I would assume you have traction control and the cornering ABS. Does not sound like either one worked for you.

Good evening. I had a interesting thing happening during the FART event with my ABS on my 2018 R1200RT-LC.

Does anyone know at what speed the ABS stops working? Or other wise said how fast (what speed?) do you have to be moving for the ABS to start working?

So what is the minimum speed for ABS to activate?

Morning Bernie

Most automobiles stop the ABS function at around 2-4 mph (if they didn't then you could never fully stop the automobile) but a car or light truck doesn't fall over if a wheel stops turning so it's possible that BMW has raised the ABS cutout speed slightly on the 1200wc road bikes.

It's also possible that on your downhill loose surface endeavor that you had enough engine/driveline drag to prevent the rear wheel from spooling back up once it stopped turning, or once it slowed below forward travel speed.

I rode an early 1200wc for a while & never noticed a higher ABS cutout speed but I ride mainly level gravel & dirt on a the RT bikes.

I do have a friend with a 1200wc GS-A & his bike is just the opposite as I have to turn the ABS off on that bike to get it down a steep loose surface hill & retain any sort of low speed braking control. That bike is a handful coming down a loose surface steep hill without de-activating the ABS as it has no braking at all in ABS mode.

You can probably do some testing on your bike either on loose gravel or wet grass (wet grass is a real good testing surface as rear wheel lock-up comes easily).

If you test your bike then please post it here as it would be good to know what BMW has programmed into the new bikes.

I have had some similar things happen. I too think the debris and wet conditions have prevented the wheel from gaining revolutions after the downshift stalled it. Not really a fault of the bike, just dynamics of riding conditions. ABS really doesn't help any in this condition. Once the tire stops turning there simply isn't enough traction to get it back to speed.

Thank you all for your replies.

I will have to be a little more careful, as the extra power of the motor and the powerful brake system can cause all sorts of stuff to happen.

At least the bike did track straight and the chassis didn't get upset during the transition from a sliding rear wheel to a rolling wheel.

Every ride is a learning experience.

I will keep you all posted if I figure anything else out.

I think Bernie is nearer the mark with the anti-hopping clutch failing to keep the rear-wheel in motion.

I think Bernie is nearer the mark with the anti-hopping clutch failing to keep the rear-wheel in motion.

I have never seen a reference that R1200RT LCs have "anti-hopping" clutches. I'd love to see a link.

If by "anti-hopping" is referring to "slipper clutches", see this description https://en.m.wikipedia.org/wiki/Slipper_clutch.

I see Bernie is in Florida. Anybody who has ever driven a manual transmission car on an icy road knows if you downshift a manual transmission car to too low a gear and release the clutch, the drive wheels will lock up (cease rotating) because there is not sufficient traction for the tires to grip the road surface. A slipper clutch would not help in this situation because the drive tire still needs to grip the road surface for the slipper clutch to work.

From the information Bernie provided, I believe he simply downshifted and released the clutch while the rear tire was on wet leaves and there was not sufficient traction for the rear tire to grip, so it locked up. It had nothing to do with the ABS not working, nor with the RT's "slipper clutch" (which the Rt does not have as far as I know) 'failure.'

Of course, this is armchair diagnosis, and I could be entirely wrong.

Tim

I think Bernie is nearer the mark with the anti-hopping clutch failing to keep the rear-wheel in motion.

 

I have never seen a reference that R1200RT LCs have "anti-hopping" clutches. I'd love to see a link.

 

If by "anti-hopping" is referring to "slipper clutches", see this description https://en.m.wikipedia.org/wiki/Slipper_clutch.

 

I see Bernie is in Florida. Anybody who has ever driven a manual transmission car on an icy road knows if you downshift a manual transmission car to too low a gear and release the clutch, the drive wheels will lock up (cease rotating) because there is not sufficient traction for the tires to grip the road surface. A slipper clutch would not help in this situation because the drive tire still needs to grip the road surface for the slipper clutch to work.

 

From the information Bernie provided, I believe he simply downshifted and released the clutch while the rear tire was on wet leaves and there was not sufficient traction for the rear tire to grip, so it locked up. It had nothing to do with the ABS not working, nor with the RT's "slipper clutch" (which the Rt does not have as far as I know) 'failure.'

 

Of course, this is armchair diagnosis, and I could be entirely wrong.

 

Tim

 

Good morning Tim.

Here is a direct copy from BMW Motorrad website discussing the features of the transmission and clutch in the WetHead motor design.

“

The drive, which is used in the R 1200 GS for the first time and is the first series opposed-twin engine by BMW Motorrad, has a multi-disc oil bath clutch with eight friction discs in place of the previous single-disc dry coupling. The benefits of this solution are both less inertia torque due to the significantly lower exterior diameter of 147 millimetres (R 1200 GS previously: 180 mm) and a more compact design overall. For the first time on an opposed twin-engine, the clutch system is equipped with an anti-hopping mechanism. With this less engine braking torque is relayed to the rear wheel in overrun so that the motorcycle remains even more stable and safer-to-handle during braking.“

Yes, I live in Florida, but I learned to ride and drive in West Germany and I am very familiar with driving in snow and ice.

I know that the traction was limited and I don't blame the design of the bike for the locked rear wheel. I did not just ham fisted release the clutch, but I eased it out. I have done similar maneuvers with my 2007 R1200RT, with out any results like this.

https://www.bmwmotorcycles.com/en/discover/engineering/technology-detail/motor-drivetrain/integrated-transmission.html

I don't see where BMW is listing the 2018 RT model excluded from these features.

Just saying!

Lol

Bernie,

I respectfully defer to your experience and observations.

And thank you for providing the anti-hopping reference. However, may I comment that even with a vehicle equipped with an anti-hopping clutch, wouldn't it still be possible that under little or zero rear tire teaction, the anti-hopping clutch would still be unable to prevent rear wheel lock up?

If you have zero rear tire traction, there Is no technology in the world that can prevent rear wheel lock up. At least, that's my (admittedly miserable, according to my wife) logic.

Again, I could be entirely wrong.

Tim

Yes Tim, you are correct. And as I was releasing the clutch lever I was thinking about it. But before releasing the clutch lever, it had plenty of traction for the brakes being applied.

I was aware that the sliding of the tire may happen, it just surprised me that ABS did not try to relieve the braking pressure on the rear tire. I could not feel the normal pulsating of the brake lever.

Regardless, it was great that the bike tract straight and it did surprise the rider following me. I just need to be a little bit smoother. Working on it.

Yes Tim, you are correct. And as I was releasing the clutch lever I was thinking about it. But before releasing the clutch lever, it had plenty of traction for the brakes being applied.

I was aware that the sliding of the tire may happen, it just surprised me that ABS did not try to relieve the braking pressure on the rear tire. I could not feel the normal pulsating of the brake lever.

Regardless, it was great that the bike tract straight and it did surprise the rider following me. I just need to be a little bit smoother. Working on it.

Bernie,

Thank you for clairfying and confirming my armchair analysis.

I had incorrectly interpreted your post (#102521 above) as blaming the cause of your rear wheel lock up being the result of your BMW's ABS and/or anti-hopping clutch's technological failure. And as you have now confirmed, it wasn't technological failure, but simply the lack of rear tire traction that caused the rear wheel to lock up when you downshifted and released the clutch.

My mind is now at rest. Your explanation should now end this thread.

Cheers.

Tim