ABS "fail safe" Mode

[DaJuice]

I bought a new 08 FJR in February this year. A few weeks ago I was getting ready to take off from a stop and another biker slipped on some sand and tipped. His pillion fell off and hit my front fender with her helmet. He was pinned under his bike so I jumped off mine and picked his off him and make sure the passenger was OK. In all the excitement I forgot my bike got hit so I didn't check it.

I took off through town about 40 mph and the next couple events happened so fast that I'm not sure I have them in the right order. My bike felt low on power so I twisted the throttle a little, I saw smoke come from somewhere under me and I came to an instant stop with out touching the brakes. I was sitting in the middle of the road not able to move my bike and the ABS light was blinking or solid, I don’t remember. I turned the key off which allowed me to move my bike. I got off and saw the front fender pushed down into the tire and the tip of the fender was molten. I pulled the fender off the tire and part of the molten plastic stayed on my glove. As I looked at the fender I realized there appeared to be a place for 2 bolts on either side of the bike behind the fork and there was nothing there. I had installed some PIAA lights mounted on the front 2 bolts and they were so loose from the factory that I didn't even need the screw driver to get them out. I can't remember if there were ever any bolts behind the fork or if they were just so loose too they fell out. I tightened the front ones down really tight on the side of the road so it wouldn't happen again and took back off and everything was ok the rest of the day.

I took it to the dealer a couple days later and explained what happened. They are going to fix the fender for free as it was definitely due to the missing bolts. I asked them why my ABS system would have done that and they explained to me it probably sensed the extra resistance on the front tire and went into its "fail safe mode." Still, does anyone else think that is a very dangerous situation and that is not how the system should react, what if I had been at highway speed going around a corner, I almost went flying over the handlebars doing 40 in a strait line. Has this happened to anyone else? Did I maybe miss something since it all happened so fast that explains why this would be a good thing?

I think I'd rather have an orange light telling me to check something than get thown off the bike.

 

[wfooshee]

The ABS sensor doesn't sense "resitance" to rotation at all, just wheel speed. If one wheel is at a different speed than the other, then the ABS triggers. That's it.

But with the fender flopping around I don't know that the sensor would stay healthy through all that. Especially if it got a taste of that melting burning plastic.

The fender rubbing isn't enough to stop the bike. Something else got jammed up. The ABS system is not capable of applying the brakes only releasing on impending lockup, so if it was brakes dragging, that came from somewhere else.

 

[DaJuice]

OK, you are right, bad choice of words with resistance. However, an ABS system does way more than releasing the pressure on the brakes. Once it notices a wheel spinning drastically different from what it should be compared to the others it modulates the pressure to that brake. To modulate the pressure it needs to apply the break, so an ABS system definitely has the capability of doing this. What I'm trying to understand is why the fail safe mode would be to apply the brakes to make the bike come to a stop.

It is possible that the fender situation was a coincidence but after what happened I was gun shy about taking any turns at speed so I found some gravel and tested the ABS system. It worked as it should so the sensor is working. Maybe it was a momentary failure in the sensor, still, why would the manufacturer make this situation the fail safe?

 

[charismaticmegafauna]

<snip>...an ABS system does way more than releasing the pressure on the brakes. Once it notices a wheel spinning drastically different from what it should be compared to the others it modulates the pressure to that brake. To modulate the pressure it needs to apply the break, so an ABS system definitely has the capability of doing this.

I'm certainly no expert on FJR ABS; but to clarify: Webster -- 'modulate', to change intermittently the frequency, amplitude...

Still, I don't think the ABS can supply more braking pressure than the rider is asking for...?

I'm quite willing to stand corrected on this (provided a salient explanation attends).

...why would the manufacturer make this situation the fail safe?

I'm pretty confident that The Forum can provide answers/resolution to this.....

I'll be looking forward to the 'education'. B)

 

[lnewlf]

ABS can only release a brake that you have already applied. It can't apply brakes on it's own. The ABS computer compares wheel speed and repeatedly releases [pulses] brake pressure to the slower wheel. Failsafe mode means that the ABS system does not operate at all because of some problem and you now have conventional brakes.. If for some reason the caliper overheats it could possibly lock a wheel though usually the oposite happens.

 

[FJRBluesman]

The way I understand ABS is, the alleged re-applying of the brake you speak of is the still constant force being applied on the lever (or brake system). If you have no pressure on the rear brake, it should not apply it for you.

As for a "fail safe" mode, that sounds incredibly dangerous (even if it could so this) to me to bring you to a stop at any time or speed. Any ABS failure short of leaking is just not going to give you any ABS stopping ability.

 

[wfooshee]

To reiterate, the ABS cannot apply brake pressure. The modulation you speak of is only instaneous release of pressure at the wheel approaching lockup. It basically takes the brake pressur being applied at that wheel and takes it into its own reservoir (which releases that brake and allows the wheel to unlock) then switches the regular hydraulic circuit back in, allowing the brake pressure you have applied to return to the caliper. It's capable of doing that several times a second.

There is no "failsafe" ABS mode which will apply the brakes to stop the vehicle. It just can't do that. The only thing in thw ABS that could be thought of as a failsafe is the system disables itself if it detects a sensor problem. Your brake dragging came from something else, but we don't know what, yet.

 

[SkooterG]

Agreed. ABS does NOT apply brakes, or brake pressure. Only temporarily releases brake pressure - modulates.

In dajuice's case, if your fender was hot enough to become molten and smoke, and it was surely putting enough pressure to 'brake' the bike quite heavily.

There is no such thing as an ABS 'fail safe' mode that would apply the brakes. Your dealer is a moron.

 

[charismaticmegafauna]

.... Your dealer is a moron.

That would be: Hitching Post, Moon Motors, Leo's, ??? :huh:

If your dealer also sells BMW, that could easily explain their ABS confusion.

My BMW riding friends say that the best thing to come along lately for BMWs is the ABS 'defeat' switch.

 

[DaJuice]

I won't say who, as I've had a bad experience with almost every dealer in the area so don't want to single this one out. I'm going there tomorrow as they have my new fender. I posted this as I, like you, can't believe this was the case and I want some ammo as that sure scared the #$%& our of me when it happened and I want to make sure it don't happen again when the conditions are less ideal. I just find it incredibly odd that as soon as I turned the key off I was able to push my bike, before I turned the key off there was no moving it.

 

[wfooshee]

That sounds like the ABS refused to release, and even after releasing the brake lever pressure remained. That's extremely odd. I don't see how the ABS system can override and increase lever-applied brake pressure.

Ah! here's an explanation. you subconsciously refused to release the brake lever, but you had to to reach the key. That's when it was able to move again.

(Joking. I don't seriously think you or anybody else would be that . . . . . unaware.)

 

[mr.paul]

OK, because you are somewhat in my neck of the woods, I am curious.

ABS only releases the brakes. A sophiticated traction control or stability control systgem can apply the brakes. FJR's don't have this. My wifes car does. Hopefully keeps her out of trouble and from doing burnouts in town.

I think a combination of a dragging fender and maybe molten fender in the caliper had you going...or not.

paul from Minnesota

2006 FJR

 

[Zorlac]

"I just find it incredibly odd that as soon as I turned the key off I was able to push my bike, before I turned the key off there was no moving it."

Dumb question, it's not an AE model is it?

 

[DaJuice]

wfooshee, I hear ya. I immediately assumed operator error (and I've seen enough posts that make you go WTF to know that stuff like that needs to be said). Again, everything happened so fast that I don't recall everything for sure, but I don't think I ever touched the brakes. I was too busy trying to stay upright, I never did get the clutch pulled in and the engine died when I came to a stop. I wanted to get off the road so I started the engine back up and let the clutch out and it wouldn't move. I shut the engine back off with the key and it rolled freely. I normally ride sweep when I'm in a group which I was doing this day so no one I was riding with saw any of this. I'm not sure if the smoke I saw was from the fender melting or if I was doing a burnout with the back tire when I tried to compensate for what ever was making me stop. I didn't notice any rubber on the road where it happened which makes me think it was from the fender.

I've got 6,600 miles on the bike since this riding season started in the great white north and this is the only incident.

 

[DaJuice]

"I just find it incredibly odd that as soon as I turned the key off I was able to push my bike, before I turned the key off there was no moving it."
Dumb question, it's not an AE model is it?

Ha, no it is a manual, but that would have been a good point if your saying the AE's go into neutral when you turn the key off.

 

[Crash Cash]

Well, the broken ABS on my Camaro sure as hell was able to apply the brakes full on if you touched the pedal at all. It was able to lock all 4 wheels instantly the moment the brake lights came on. It spun me out on a freeway on-ramp and that was the end of my car days.

It also would release the brakes fully between 20-25mph, then lock them fully in a cloud of blue smoke when it coasted down below 20mph.

According to the OBD-II it was a bad front wheel sensor ring which I couldn't get the dealership to fix. I AM SO GLAD that GM is going into bankruptcy.

I don't know if the FJR has any similar failure modes, but that's why I was really really leery about buying a bike with ABS.

EDIT: This was '92 or so, before traction control, it only had ABS. As a matter of fact, it didn't even have full OBD-II, I think it was the first year for that.

 

[Geezer]

Well, the broken ABS on my Camaro sure as hell was able to apply the brakes full on if you touched the pedal at all. It was able to lock all 4 wheels instantly the moment the brake lights came on. It spun me out on a freeway on-ramp and that was the end of my car days.
It also would release the brakes fully between 20-25mph, then lock them fully in a cloud of blue smoke when it coasted down below 20mph.

According to the OBD-II it was a bad front wheel sensor ring which I couldn't get the dealership to fix. I AM SO GLAD that GM is going into bankruptcy.

I don't know if the FJR has any similar failure modes, but that's why I was really really leery about buying a bike with ABS.

EDIT: This was '92 or so, before traction control, it only had ABS. As a matter of fact, it didn't even have full OBD-II, I think it was the first year for that.

Camaro had power assisted brakes. There is nothing on the FJR that applies brake pressure besides the operator.

I intentionally chose an FJR without ABS because I had the ABS on my Chevy truck kick in one time when it shouldn't have. It was a low speed slop at a toll booth, the ABS kicked in and I almost ran into the guy ahead of me.

 

[lnewlf]

Don't see any way ABS on anything can apply the brakes. As Geezer noted, unneeded ABS activation can increase stopping distance by releasing brake pressure. Premature ABS ejactivation is almost always caused by corrosion on the tone wheel or hall effect pickup sensor ,easily cured by sanding with emery cloth. I had a Monte Carlo that would occasionaly lock the right front when the pedal was touched and almost spin the car-replaced everything with no luck-probably a metering block but I can't blame it on ABS-didn't have it..

 

[Dragan]

ABS "fail save" does not exist. In case of any failure with the ABS system, you only loose ABS control (pulsing, releasing oil press) but you have conventional brakes.