edited Kristian #562 & NickJC # 085i
Many Thanks to Andy #982 for his fantastic Knowledge of Brakes and ABS
Please read the Disclaimer before attempting any work in this FAQ.
Last Updated: 23 March 2007, by Winter #1935
For other related FAQs:
Fuel injected F650's (GS/Dakar/CS) and G650X's have optional ABS (Anti-Brake Skidding, or Anti-lock braking). ABS is designed to reduce the risk of your brakes locking up and causing a rear or front wheel lockup. The system on the F650's is a simply two channel Bosch system - there is no linkage between the front and rear brakes. In other words - if you grab a huge handfull of front brake, the "excess" braking will not be transferred to the rear brake.
The ABS system on our bikes is known as the ABS-N. It is manufactured by Bosch, and the ABS-N ECU was made by Nippon (according to readouts from a GS911). The diagram at the right shows the ABS-N system components in detail.
|ABS Is No Substitute|
ABS is no substitute for good ol' fashioned braking skills. If you have ABS, do not get lazy - practice braking by turning off the ABS from time to time, and practice your skills in a controlled environment. Also practice heavy braking with the ABS enabled - this will help you understand what it feels like when the ABS engages. This is especially important when you have never experienced the ABS engage.
Also keep in mind your stopping distance. Just because you have ABS, it does not mean you can sit closer to the vehicles in front of you. At a very minimum allow 3 seconds in good conditions. While this is not always possible, it is a good idea to remind people about braking distance.
|Look Ma! NO BRAKES!|
If you have been working on your brakes, be sure you test them in a safe and controlled environment. If you position the sensor too far from the sensor ring, you may encounter a situation where you have no brakes - this is particularly true on the front brakes (on the rear you will notice other strange behaviour such as an erratic speedo). The following is a quote from someone who has experienced this:
It was VERY scary. At the first squeeze of the lever, it began pulsing and there was ZERO brake force being applied. It didn't have anthing to do with stuck pads at all. After about 100 yards of travel, the ABS unit realizes something is out of whack and disables itself and the brakes function normally again. ... It was due to the gap on the abs sensor being too wide. I removed the shim and all was well. ... gsatlanta
The Speedo, Fuel Injection system and ABS are all affected by the two speedo sensors, and are particularly sensitive to the clearance between the sensor and the sensor ring.
|General Notes and Hints|
|Note 1. The ABS can't be deactivated while moving. This prevents the ABS from accidental deactivation due to a wiring fault in the switch etc.|
|Note 2. If you are having a hard time turning off your ABS, just rock the bike backwards or forwards a few inches (it wouldn't even take that much) and try the regular procedure again. (Seacuke #1214).|
|Note 3. If you hold the ABS button too long, the ABS will reactivate, and you will need to turn the bike off and on again before you can disable the ABS again. This is a safety feature in case the button is broken, and results in the ABS being enabled by default (if possible).|
|Note 4. If the ABS light does not start flashing after a few seconds and Note 2 does not help (rocking the bike back and forth a bit), the wiring on the switch may have come loose.|
ABS does NOT actually lengthen the theoretical stopping distance. ABS only kicks in when the wheel is already locked. It unlocks it. A good rider will be unaffected by ABS since he can modulate his breaking before the wheel locks up and the ABS kicks in and starts pulsing the breaks.
So to reiterate. If you are a super-duper motorcycle god ABS will be invisible to you. When the young child runs in front of your bike by the school or when you realize that there is stop sign you didn't see or when the car in front of you drops its tranny you will modulate your breaks and defeat the lock up. For the rest of us we can grab the front breaks in and mash the rear pedal and stop with out worrying about a low or high side from the skid (or the skid not stopping us fast enough and we kill the kid, run the stop, or hit the new transmission laying in the road in front of us...)
For any who doubt this look at how the ABS works. Your front and rear wheels have optical sensors the use a slotted ring. If one wheel is spinning and the other is stopped and the breaks are on the ABS can pulse the locked up wheel's brake. This in NO way interferes with an EXPERT from stopping the bike really quickly because the ABS can only detect a lockup... It can do this faster then a person can but it can't (not with the system on the GS) intervene before the front and rear are spinning at different rates (only really possible with one wheel either locked or almost locked.) Some ABS systems can do prediction. however, the system on the GS/Dakar isn't that sophisticated.
Now to put it succinctly ABS is reactive. ABS won't do anything unless YOU the rider has already screwed the pouch by grabbing front brake before the weight transfer or holding the rear after the weight is transferred.
Just a couple of points, ABS sensors are inductive not optical. The sensor ring makes a voltage and a sine wave amplitude. This gives all sorts of information about the wheels condition as well as rotational speed. ABS cycles in deep slip not at the point of wheel lock. Any braking involves slip. To simplify the bike does 100 kph, the wheels turn equivalent to 99 kph you have slip and hence braking.
A locked wheel has 100 % slip. Above 80% slip the brake force actually drops and the wheels ability to transmit side forces becomes low. You cannot steer and have no centrifugal force to help balance. ABS aims to stay in the 5% slip region below the uncontrollable zone. As 80% slip is exceeded it lets the brakes go but then immediately reapplies to try and get back to the maximum braking point. Hydraulic systems are slow a rider is slower. A typical full ABS cycle on air is 0.02 seconds. To pass EC/98/12 an ABS system has to equal 75% of the deceleration achieved using micro adjustment valves. You do the same stop time and time again adding a 0.1 bar pressure on single wheels until the wheels lock for more than 0.25 sec. Then you do an ABS stop and compare the deceleration. Who says test tracks are interesting (yawn)!
My original post is correct about the theoretical stopping distance. If some one was lucky enough to hit 80% slip and stay there they would beat the ABS cycling between 75 and 82 %. If such a person exists they'll be taking over the world not playing on F650's. The rider who can beat ABS first time out is a job for geneticists not engineers. Theory and practice are separated by the human element.
Weight transfers off the rear wheel making it unable to transfer torque to energy to the road. The tyre contact area gets smaller, the brake torque is high, the wheel does into deep slip and ABS cycles. Weights transfers onto the front wheel, increasing tyre contact area. You have to brake very very hard to exceed the available grip at the front.
|ABS Switch||Remove the ABS switch and use something to touch the wire contacts together. This is a "normally open" circuit.|
|ABS fuse||Check for a blown fuse.|
|ABS Warning Light||When you turn the key to the on position, the ABS light should turn on for a brief period. If it does not, you probably have a broken globe. If I recall correctly the ABS-N unit will detect and report this fault, so the GS911 should also pick this fault code up.|
|Battery Voltage||Check your battery voltage with the key in the on position, engine off. A 12 volt ABS system typically needs 11 to 15 volts to work. Any less and it cannot tell the 1's from the 0's on digital signals. Check the Battery FAQ for more info.|
|Front ABS Sensor||Check the gap, and check for damage to the sensor. Also check the wire is not damaged, and check the connector tucked up behind the LHS indicator (it is easier if you remove the LHS cover). The GS911 will also detect incorrect signals from the sensors.|
|Front ABS polewheel||These are the toothed wheels on the hubs. Check for chips and missing teeth. Make sure the sensor cannot move in relation to the polewheel. If the signal is not believable, the ABS will shut down. The system needs vehicle speed to work out which wheel is locked.|
|Front brake lever switch||There is a small POS switch on the front brake lever. When you pull the brake lever, this switch activates to tell the ABS and brake light you are braking. If this switch is not functioning, it may affect ABS. The quickest way to check is to see if the front brake lever affects the brake light.|
|Rear ABS Sensor||Again, check the gap, and check for damage to the sensor. Also check the wire is not damaged. The connector for this sensor is next to the BMS-C on the LHS of the bike. Problems with the Rear ABS Sensor will also have other symptoms such as erratic speedo problems, and surging and stalling - this is because the Rear ABS Sensor is also used as the Speedo input.|
|Rear ABS polewheel||See comments for the front ABS polewheel|
|Rear brake lever switch||There is a small POS switch on the rear brake lever. When you push the brake lever, this switch activates to tell the ABS and brake light you are braking. If this switch is not functioning, it may affect the ABS. The quickest way to check is to see if your rear brake lever affects the brake light.|
|ABS modulator valve||This will fire as a test when you set off. If you do this with the rear brake lightly depressed you will get the feed back into the pedal. If the system is active when it should not be (eg low speed, high grip surface stops), you have a sensing problem. A modulator or electrical problem would be detected by the ECU and the warning light would come on.|
|ABS modulators||Do the modulators fire when you first turn the bike on. You should hear a moderate clunk clunk from the ABS unit. If you have a GS911, you will also hear the clunk clunk each time you query the ABS-N unit itself.|
|Brake light circuit||With the key in the on position, engine off... check the brake light turns on and off when you engage the front and rear brakes. If your rear brake light is permanently on, or does not work for one brake lever, you have a failed brake lever sensor. The ABS looks at the vehicle all the time but will only calculate wheel decelerations and fire modulators together during a brake application. If a brake light is stuck on, the system will eventually decide this is a failure and shut down.|
|ABS-N ECU Query||If you have a GS911, or know of someone with one, these devices can query the ABS-N unit for fault codes, and clear them if required. See the Fuel Injection FAQ for more information.|
|Basic ABS Sensor Checks|
You can do a basic test yourself. Unplug the sensors (ignition off) and connect a voltmeter to the two connections on the sensor. Spin the wheel and look at the voltage produced by the sensor. Both sensors should produce the same voltage at the same RPM (typically 0.5V at 30 rpm, but that will vary with sensor types). Voltage should be steady for a steady speed.
Also check for rusty connections, bent pins, or water in the connectors to the sensors. Other things to look out for are split or worn wires.
|ABS light not turning on||1. No ABS on your bike|
2. ABS Warning Light Globe Broken
3. Dash fuse or ABS Fuse Broken
|Can not turn ABS off||1. ABS Switch wiring damaged|
2. Try rocking bike back/forward a little bit
|ABS light starts flashing|
(once / 4 seconds)
|1. You have turned the ABS off|
2. Broken ABS switch or wiring
|ABS light flashing|
(faster than once/4 seconds)
|1. Unknown error / fault|
2. Front / Rear ABS sensor problem
3. Main ABS unit problem
4. Perform full system check
|ABS light on||1. Unknown error / fault|
2. Low battery voltage
3. Perform full system check
|Erratic speedo, bucking,|
or surging and stalling
|1. Rear ABS/speedo sensor fault|
2. Water in connectors
3. Loose battery connections
4. Perform full system check
|ABS pulsing, Brakes fine if ABS disabled|
No bucking / surging or speedo problems
|1. Check the rear brake lever switch|
2. Check the front brake lever switch
|Zero front braking, ABS active|
ABS fault after a short distance
|1. Front ABS sensor fault (check gap!)|
2. Water in connectors
3. Perform full system check
Just stumbled across the following lines from a site
on the web and thought I'd pass it along to those who might be interested. (full
article at link shown below). Having ABS, I mashed both brakes during my riding
exam, and came to a pretty good stop. If ABS allows me to use both brakes to
their fullest capability, then I guess I like ABS. Scott, ID
According to the American Motorcycle Safety Foundation, if you try to get the best out of both brakes in an emergency, you will get the best out of neither. The MSF says you can't concentrate FULLY on both brakes at one time. You know your mother's old nag, "You can't concentrate on two things at one time"!
So, to get the best braking, you have to concentrate using either the front or the back brake and, since the front brake gives up to 80% of your braking power and incorrect application is likely to make you fall off, it makes sense to concentrate on the front brake.
The American Motorcycle Safety Foundation teaches their instructors that "in an emergency braking situation you should apply the back brake hard and let the back wheel slide if it wants to. This way you can concentrate on what is happening up front; there's enough to think about in the use of the front brake."
I think my brain is pretty cool. It has this one section, called the "autonomic brain center" that does a lot of stuff for me that I don't have to think about, like breathing, heart pumping, etc. The brain takes care of other things, too. A lot of times, all I want is something done, like, pick up a pencil and I don't even have to think about what muscles to move and when, I just decide to pick up the pencil and the ol' brain just puts all the pieces together and voila, the pencil is picked up. The consciousness center of my brain basically decides what I want and then the motor section coordinates all the details without the conscious having to tell everybody what to do. I like this arrangement. Same thing happens when I want to stop my bike. I just want it to stop and the brain does the rest. It knows what levers to pull or push and just does it. I really don't have to 'think' about it, I want it done and the brain takes care of all the details. I think this is why I had a big problem in the braking exercises during the experienced rider MSF course. They didn't like it when I said I never 'think' about braking, I just do it. They tried to get me to "concentrate" on this or that but I just couldn't. Of course, I came to a stop where they wanted. They didn't think I was "concentrating" enough or looking in the proper direction but I passed all the tests. The worst part was the rear wheel skid thing. They wanted me to keep skidding the rear tire until I came to a complete stop. It was very difficult to do this because my brain instinctively told the foot muscles to slowly let up on the rear brake pedal when the butt detected a skid (a distant skid, not local). It took several tries but I finally succeeded in having the rear tire skid to a stop. I was glad I could do it but I've never done it since. Doesn't make sense to me. But MSF swears by it. These are the same MSF people who like to critique my riding, unsolicited, while leaning out the window of their cars at various intersections of this fine city. They ask if my F is my "first bike." Nope, it's like the eight or ninth one, I stopped counting a while back. If they don't ride here, what makes them think they can tell me how to ride here? Ya know, I've had a bike with ABS. It caused a lot of problems, especially on slippery surfaces. My brain and I didn't like the bike's ABS computer doing the thinking for us. I got rid of that bike. And it is well known that certain moto magazine editors in the USA can stop comparable bikes in less distance WITHOUT ABS than with ABS. I'll keep my brain and my non-ABS bike until some unelected unaccountable tolerant open-minded liberal bureaucrap in California makes it impossible for me to choose a bike without ABS. I'd suggest you don't "use your brakes" but that you simply stop your bike. And practice stopping it WHERE you WANT it to stop. Shank NYC USA
For me the proof was in the pudding at the last braking and cornering course I did with Top Riders (Qld Australia) at the Darlington Park Race Track. By the end of the day after a lot of tuition and practice, front brake only, back brake only and combinations I was stopping from about 120k around 20 to 25 metres shorter than when I started. I have been riding for a while and was really surprised and pretty happy with the results. Tuition by experts and practice wont do any harm unless you come out of it under the delusion you are bullet-proof. Ratso
I also agree Shank, all except the part about not wanting ABS. I never trust the ABS to save me, if it activates I consider myself to have failed braking. If the rear wheel ABS activates it's no big deal, but if the front wheel ABS would activate, I would realize that it might have saved me from crashing, and start practicing my braking skills more often. Braking by reflex? Yes I fully agree, and you can train your reflexes! By the way, the difference between genders is smaller than the difference between individuals, so don't believe that only a woman can do two things simultaneously. Let me give you an example, men are usually taller than women, but some women are taller than most men. rakaD
Shank is (predictably) right on: the skill should be developed to a level where it "just happens." Those who practice martial arts, baseball, etc. etc. spend hours honing their respective skills so when their time comes to to perform, they react with precision and skill without thinking about it. Why should a motorcyclist, whose life may depend on his/her skill level, settle for less? The MSFs claim that you can only do one thing at a time might very well apply to a nervous, shiny new rider, but personally I can't begin to agree that it applies to anybody else. Better to teach the new rider to coordinate hand and foot, rather than take the hopeless position that only one body part can be trained to respond. Absurd! As for ABS: >And it is well known that certain moto magazine editors >in the USA can stop comparable bikes in less distance >WITHOUT ABS than with ABS. I don't doubt that, but I'm no expert track rider, nor do I think I have the presence of mind (just yet) to rely on the autonomic response to be in prime condition during an unexpected event. Until then, I suspect my ABS is more reliable. I think. Actually, a co-worker and I discussed this recently, and his recollection of the "expert rider" comparison was that yes, they could stop faster WITHOUT ABS under CONTROLLED conditions. But, and this is second hand info, but these same riders apparently would prefer to have ABS on their bikes, admitting their brains will not likely perform at 110% during an emergency, that they might not be able to "process the feedback" well enough when it counts. I haven't read these articles, but this was what I was told.
Females do have a much more highly developed corpus collosum than males (these are the nerve fibers that link the two hemispheres of the brain). As with any upgrade/modification, it does have its advantages and disadvantages. It makes them much better communicators but hampers spatial tasks and concentration and to some extent, hand-eye and hand-hand coordination. Now before anyone gets their knickers in a knot, this is not the case with ALL XX chromosome types. But I did once have this very smart, very communicative girlfriend (who became a lawyer, which requires excellent communicative skills and linking A and B together) but she could not pack her bags, or arrange boxes in the trunk of her car and watching her trying to use a manual egg beater was hilarious (laughing got me hit, hard, with pudgy little girl fists, which only made me laugh harder, then the brick got dropped in the purse and I was summarily whacked). I haven't practiced braking in a while but what I used to do was go into an empty parking lot with two colored stones or whatever for markers. I would put a marker out, ride up to it at some pre-determined speed and then hit the binders for all I was worth (skidding not allowed) and where I stopped I'd place the other marker. Then I would try it again and try to stop before I reached the second marker. It's tough and can be frustrating. But practicing either brake by itself was something I never did. I will try that next time I do braking practice. Thanks for the idea, Ratso. Lately I've been working on choosing and maintaining a cornering line. Maybe it's time for some braking practice. Shank NYC USA
I think Andy Leeds had the best comment about ABS. if ABS kicks in, that is a signal that you've overdone something and made a mistake. Always brake as if you don't have ABS, and then be very glad that you do if it kicks in. Regarding the rear brake, it DOES have some stopping power at the very beginning of the braking cycle, before the weight has shifted forward, but after that it will add nothing if you are using the front brake to it's limit. Mason #631
The rear brake is going to provide some force. Braking is about the friction between the tyre and the road, the brakes been able to produce a massive amount of friction by comparison. The friction at the tyre is a factor of road surface (Mu) and contact area. Contact area is related force that flattens the tyre down onto the road. Mu depends on the road maker and the weather. BTW get those tyre pressure right too if you want to brake hard. The front has all the advantages. The weight transfers onto it. This is why lots of bikes have two disks on the front. The rear has weight coming off right to the point where you do a stoppie, its only advantage is that if it locks, its tendency to accelerate past the front takes time to become critical. With a 50/50 brake split static, the front typically produces 75% of the force. If you want to do this scientifically for your riding measure the disk temp. Temperature is related almost directly to the amount of work the brake did. Brakes mostly turn kinetic energy into heat. The ABS is going to find the critical area where slip is maximised without loosing sideforce etc. But, and it is is a big but, if the rider panics (like the magazine editors) and tries to beat the system, it cannot work as designed. If you release or modulate the pedal, the system must assume you have finished braking. The rider beats the ABS but not in a good way. Cars can have brake assist where this reaction is detected and ignored, but on a bike, this is going to be difficult to get right and so is not yet available (that I am aware of). With ABS, forget technique, just squeeze the controls and ride. You still need to be able to ride non-ABS for that day when the fuse blows. Non-ABS, we are taught a totally different technique in the UK to that described on MSF. You apply the front brake until you feel deceleration, then the rear, then feed in both until you have enough. That said, there are a lot of riders (mostly cruiser riders) who think the front brake is too hard to control (fear a lock) and other (typically sports types) who never use the rear (fearing a slide no doubt). You need to be able to use both. You need to be able to find (but not pass) the point where the front is in too deep a slip to control. You also need to ba able to detect and react to a rear wheel lock. Mostly you need to be able to decide in an instance if the surface will take the braking you need. If you have space to risk locking the rear but going down would be lethal (motorway lane), give priority to the rear control and only give the front what you know it can take etc. Given you have to make this decision in an instance, I'd tend to agree its a feel thing and practice is best. Women do tend to be better at multi tasking. As a result, they can be better riders and drivers. The big advantage they have is that they identify the risk sooner and prioritise the response. Braking technique apart, if they (or a man) brake sooner, you'll get away with less skill at skid control. There is no reason a guy can't achieve the same level, we just need to practice more. British Army 6P's: PPPPPP, Planning and Preparation, Prevent P*** Poor Performance. Andy Leeds UK #982
Speaking of ABS... I'd like to hear opinions about how much of a safety factor you all think ABS is. A co-worker went down on the Bay Bridge last week. He is a very experienced rider. He says that a car came over into his lane, and despite restrained braking, his front wheel locked on the wet pavement and down he went. Luckily his injuries were minor. The bike is probably totalled. Do you think that ABS would have helped? Or is it that sometimes you hit a slick spot and there is little you can do except be prepared by wearing good safety equipment? Mr Stan F650GS
MrStan, In the situation that you described ABS definitely would have helped. In a low traction environment you don't need to be an expert to get max braking with ABS. That's the beauty of it. It takes the guess work out of the available braking traction. Tom McCallum.
Last week I was riding down a two-lane highway, a few car lengths behind a pickup truck. In the oncoming lane, I see that the driver wants to make a left hand turn across my lane up ahead. I instinctively flip on my high beams, and cover the brake and clutch. Sure enough, as soon as the truck passed her, she starts her turn. Half way through, she sees me, and stops, blocking my lane. Everything went down....clutch, brake, shifter, rear brake. Under my right hand I felt this "pulse...pulse...pulse....pulse...pulse...", and a similar feeling under my right foot. She finally gunned it, and I stopped a few feet shy of where she would have been. No doubt about it....that "pulse...pulse...pulse...pulse" of the ABS stopped me from going down. I love my ABS. Doug, '03 Silver CS.
I've ridden both with and
without ABS since it was introduced on bikes in 1988. It was an important reason
for choosing my present bike so obviously I'm positive about it. However ABS
should never be used as an excuse for not practicing efficient braking without
the aid of the anti-lock. On the GS ABS can be disabled by a switch. The front
ABS-sensor on the CS is fitted with one screw and if the sensor is removed and
tie-wrapped away you will effectively disable ABS for your practicing sessions.
Of course all the common sense things applies here about not overdoing it,
making sure there are no objects to crash into and no crowds of people around.
Having an experienced rider there to give you tips is usually valuable as well.
Good luck! Pelle F650 GSDA '02, Stockholm, Sweden.
ABS only helps significantly in a straight line stop (unlike a car, but still better than none). BMW recommends replacing rubber brake hoses (I forget the interval) as they tend to get fatigued over time. Part of the improvement people feel can be traced to having "new" brake lines instead of "tired" ones. But my guess is the steel ones are at least as cheap as new replacement BMW rubber ones, so why not improve? Marty #436-Chicago-97 F650F
I just read the ABS FAQ and thought I might mention
two situations where ABS was a factor - Any comments appreciated.
1- I Love ABS :
Recently on my wan into town after a short rain shower a car swerved to avoid something and ended up in the clear lane I was riding in, I was behind a guy driving some kind of roadster, we both hit the brakes, we were on a slow bend, I watched as his bike fish tailed under him due to the lean form the corner and the fright he got that made him lock up the rear. While he was busy trying not to dump the bike and not to soil his pants, I was able to actually steer away from him while I hammered the brakes stopping just short of the car which now had a roadster in its wing and the rider on the hood. I know you could say that a great rider could have managed this without ABS but I am willing to bet that even the best lock it up from time to time.
2 - I Hate ABS :
A pedestrian stepped backwards off the sidewalk right into my path, I was in traffic and had nowhere to go, Trusting in my god ole ABS I Clamped on the brakes, the bike began to stop BUT as far as I can tell the road surface was uneven, not slippery just bumpy, All of a sudden my brakes kick back against me so much that they release and the bike lurches forward until I can get a good squeeze - i figure that I probably jumped forward about 7 feet - enough to give the pedestrian a good thump. Without ABS I would have been fine as I would not have hit the brakes so hard (lesson learned) BUT HAS this happened to anyone else, I have since replicated this just to be sure (no pedestrians involved) and If you really hit the brakes and the road surface changes - like a seam in the concrete or a bump- it seems to really confuse the ABS and you really loose your brakes for a second. '03 F650GS, Dublin, Ireland. gkb
Every thing has pros and cons, as you note gkb, including ABS. I for one, prrefer not to have it, as it costs too much, adds extra weight, is difficult to service, is tough on the bike's electrical system, I am very careful when riding in the rain and give vehicles in front of me lots of space and I have other bikes without ABS that I ride every day and would be confused in an emergency as to which bike I was riding at the time. However, I can certainly see the value in ABS and in fact specifically ordered my car with it. I would never discourage anyone from getting a bike with ABS, it is just not for me. After 40 years of riding non-ABS bikes, I have gotten used to not having it and I am digging my heels in against the progress of new technology. Richard #230
<< I figure that I probably jumped forward about 7 feet - enough to give the pedestrian a good thump >> Yep, that is ABS behaviour when crossing a very slippery object (iron manhole cover) while braking hard. Although I think most of the time it is less than 7 feet (unless the slippery patch is big) it certainly has a worrying feel to it. The pause in the breaking actually feels as 'acceleration' to me. IMO there's no real alternative to this behaviour as well, you cannot invent friction where there is (almost) none. The F650 is my 4th motorcycle with ABS. If in the past it saved me 3 times from dropping the bike, I find it money well spend. And during normal breaking it is not in the way. On top of that on an F650 it is not heavy and reasonable priced in comparison with what it used to weigh an cost on K and R models. To me ABS is a very valuable add-on on a motorcycle and one of the reasons I ended up with the F650GS instead of an Aprilia or the like. Robin '03 F650GSA, Amsterdam, Holland.
<< I figure that I probably jumped forward about 7 feet - enough to give the pedestrian a good thump >> The bike will seem to "jump forward" if it encounters a complete loss of traction -- having no traction it will release the brake to keep the wheels rolling rather than locking. If there's really no traction there then there is nothing you could have done better without ABS -- you would have slid forward no matter what, except you would have wheels locked and may have dumped the bike instead. If there's no traction then there is no traction and no amount of brake manipulation, ABS or not, will keep you from sliding or jumping forward. You might also consider -- consider only, I'm not saying it happened -- that you could have mistaken the ABS pumping action for release of brakes. On the F650 when the ABS is activated you'll feel like the brake lever is being released and re-applied rapidly. But in truth it doesn't fully release the brakes, it eases them off only to the degree required to keep the wheels rolling. After we got our CSA I went out on the first rainy day (only a couple of days after we got the bike) and deliberately tried to lock the brakes, got the full ABS action. I wanted to learn what it would feel like on this bike and best to find out under controlled conditions (well, semi-controlled -- a public road with no one on it). Aside: Some time ago my wife, a beginning rider, watched a woman on another bike lock up the rear wheel on a panic stop, fishtail, and finally dump the bike, taking a fairly painful whack in the process and damaging the bike. Between that and having experienced how easy it is to lock the rear wheel on the Intruder my wife was riding at the time, I think it made her very leery of really hitting the brakes hard, afraid of crashing the way she'd seen the other woman do. When she started riding the CS I told her not to worry about that: "If you have to make a panic stop, don't be afraid to apply both brakes as hard as you can -- they will not lock up and you won't dump the bike the way that other woman did." A few days ago she misjudged a traffic light, ended up making a full-on panic stop to keep from going into the intersection, hit the brakes *really* hard, and...just stopped. No skid, no slide despite the grungy surface near the intersection -- just a scary moment that turned out fine. Should she have judged the traffic light better? Yes, and with more experience she'll likely be better at it, but one cannot expect expert judgment and behavior from someone just starting out (and even "experts" make mistakes sometimes). For the moment I was very glad that she, though a novice, still felt the confidence to hit the brakes full-on without fear of locking and crashing, and thereby avoided going into the live intersection, where consequences could well have been far more tragic. DesertRider '03 F650CS (hers) / '02 TW200 (hers too)
During the MSF class a few months back, my wife was constantly locking up the brakes of the bike - some exercises they encouraged it (to experience the feeling), while others she did it inadvertently. She made the comment that while she knew she was getting a bike with ABS and this wouldn't be a problem, she still wanted to get the feel of brakes locking up, etc - but also didn't want to be timid on the brakes if she needed to do some kind of a hard/emergency stop. I'll have to say that for a beginner (me and the wife), the ABS was a factor in purchasing the CS' that we ended up with.....p.s. I've only activated the ABS on my bike once - crossing railroad tracks (metal plates) and had to brake - felt the ABS kicked in - no sliding, etc. '03 F650CSA (Titan Silver) (mine) and '03 F650CSA (Graphite Metallic) (better half), Cincinnati, Ohio.
Trusting in my god ole ABS I Clamped on the brakes, the bike began to stop BUT as far as I can tell the road surface was uneven, not slippery just bumpy. I don't have ABS on my motorcycle, so this may or may not apply, but I occasionally browse a similar message board for my car (a Subaru), and lots of people there have complained about the ABS behavior on bumpy roads. The consensus there seems to be that the wheels momentarily lose contact with the road surface, which confuses the ABS sensors (I don't know if the wheels lock up for a split second, or if the wheel speed changes dramatically in some other fashion). Apparently, there's nothing that can be done, other than to be aware that this is a possibility under hard braking on rough surfaces. Just something else to think about. 1999 Cagiva Gran Canyon. Former 1997 F650 owner currently on parole. May be sent back to the Chain Gang for parole violations (i.e., test-driving a 2003 F650). Urbana, IL, USA. josh #581
I used to have a Chevy Blazer with abs (was glad to get rid of that pos) and they acted the same way over a bumpy surface. I don't believe the abs was confused though, a tire in the air has absolutely no traction, so it would take a complete absence of braking to get the wheel to turn again, which is what the abs is supposed to do. The net effect then is that over chatter bumps, the abs will turn off the brakes. This would happen during normal braking, not just hard braking, if you were going over the bumps fast enough. '01 Dakar, Nashville. SScratch
Every thing has pros and cons. I for one, prefer not to have it, as it costs too much, adds extra weight, is difficult to service, is tough on the bike's electrical systems - Richard #230
The F650 is my 4th motorcycle with ABS. If in the past it saved me 3 times from dropping the bike, I find it money well spent - Robin '03 F650GSA, Amsterdam, Holland.