why did my ABS not work?

[Matts_12GS]

I was doing an instructor session on the track yesterday and while coming down the front straight setting up for the first turn I had an issue.

 

I hit my brake marker, downshifted and started to brake and my bike started to "push" and wasn't slowing down appreciably. I dropped another gear and feathered the clutch to get the bike stopped without going off.

 

I never felt the ABS modulate, even though earlier in the day I had kicked it in during some braking drills with the students.

I pitted in and checked the bike and there was nothing visibly wrong and I did two more sessions at a more moderate pace without issue.

 

Any thoughts?

[Survived-til-now]

Matt

 

I remember another advanced rider had been on a skills day and when he came to do an emergency brake for the ?-th time the ABS didn't work and he lost the front and did a low side as a result. There was a big fuss as to why his ABS didn't work.

 

Shortly after BMW issued an amendement to the handbook (2005-ish) to the effect that repeated testing of the ABS could drain the battery and a low voltage could cause the ABS not to operate but that "in normal riding" this would not occur.......

 

So if you had lots of short runs with frequent starts draining the battery, old battery, or riding that repeatedly used the ABS (or a combination) that could be the reason.

 

Andy

[Matts_12GS]

Thanks for that reminder Andy.

 

I had been doing 30 minute sessions and did two more after that and there was no issue afterward. I am just wondering if I got in some marbles or something since I was trying to turn in deeper than the turn marker and maybe my excitement with the turn kept me from noticing the ABS cycling...

 

I dunno. I rode a whole bunch harder in the last session with my students and everything worked just fine after that.

[KDeline]

Matt

 

I remember another advanced rider had been on a skills day and when he came to do an emergency brake for the ?-th time the ABS didn't work and he lost the front and did a low side as a result. There was a big fuss as to why his ABS didn't work.

 

Shortly after BMW issued an amendement to the handbook (2005-ish) to the effect that repeated testing of the ABS could drain the battery and a low voltage could cause the ABS not to operate but that "in normal riding" this would not occur.......

 

So if you had lots of short runs with frequent starts draining the battery, old battery, or riding that repeatedly used the ABS (or a combination) that could be the reason.

 

Andy

 

 

 

 

 

 

Daniel?

[CoarsegoldKid]

Great! Now they can't make ABS worth a $hit either.

 

Matt does your model allow you to turn the ABS off so you get no surprises.

[racer7]

Depending on ABS in a track situation isn't a great idea and I doubt that was Matts intent. The point is to get good at threshold braking, the shortest way to haul it down.

The BMW ABS is slow to recover and could use some additional software and hardware development anyway- getting into it is a recipe for finding yourself faster and deeper than you intended. Makes for a good chance to practice alternate lines and recovery, though. It would help if the stock brakes had better feel- their not ideally telegraphic about what they're doing.

 

ABS real virute at the track is preventing flat spots on track tires and a few spills by the overly ham handed.

[dirtrider]

Morning Matt

 

What year/version BMW were you on?

 

The 1200RT’s have a fairly smooth ABS event with fast response times so maybe you were in ABS and didn’t even know it.

 

By you saying the bike stated to PUSH kind of sounds like you were also turning (they don’t push when going straight). If that is the case, remember that the BMW current RT ABS system doesn’t work at it’s best with the bike leaned over. The problem is the ABS system has no idea the bike is leaned over and turning. If the front tire is already using some of it’s traction for cornering the ABS has it’s hands full just trying to keep the bike from going down so you would probably got a lot of tire slippage if braking hard AND turning.

 

[Matts_12GS]

I was on my 05 R12GS.

 

Coming down the straight at about 100mph when I started my brake/downshift pattern. I got to the turn marker and started my turn and the bike was not turning, just continuing on a straight path. I applied max braking and while I did finally slow and stay on the track, I just think I would have felt my ABS cycle at that point but I didn't.

 

Either my threshold braking was right on or there was something else in play.

 

Like I said though, it worked as advertised the rest of the day, so I am perplexed to see if it is a developing situation or an anomaly.

[dirtrider]

Afternoon Matt

 

Difficult to tell from a distance but it really sounds like you were already in ABS control and it was holding your wheel slippage to right on the edge of traction so when you asked for more traction to turn it wasn’t there.

Or as you say you were right on the threshold just above ABS intervention and again as you asked for more traction to turn the tire just didn’t have it.

 

Only so much traction in a tire on a given road surface and if you are using it all for stopping nothing left for turning so they push or run wide.