F650 ABS FAQ

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

• Introduction
• General ABS Questions
  • How do I know if my Bike has ABS
  • What is ABS for?
  • Can a good rider do better than ABS?
  • What about off road?
  • What do the warning lights mean?
  • What is the most common failure/cost of ownership?
  • Should I modify my riding?
• ABS Operation
  • How do I de-activate/re-activate the ABS?
  • What about ABS on DIRT?
  • ABS & "Stoppies"
  • Can a Good Rider REALLY do better than ABS?
  • Tricks to activate ABS
  • Does the ABS light come on during ABS activation?
• ABS Mods and Maintenance
  • What is the Sensor gap specification?
  • What can I do myself to maintain the system?
  • Can I modify the bike?
  • Can I add ABS to my bike / Can I remove ABS from my bike?
  • My ABS doesn't seem to work. Is there anything I can check myself?
  • Symptom Based Diagnosis
  • ABS & Brake Bleeding. Can I still do it myself?
  • ABS & That LED
• Opinions on ABS

For other related FAQs:

• Brake Maintenance FAQ
• Brake Pad FAQ
• Brake Light FAQ
• Brake Questions Misc FAQ
• Speedo ABS Sensor FAQ
• Fuel Injection FAQ

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.

• 
• If your bike looks like this one, where the red circle is, then it does NOT have ABS.
• If you have a look behind the Cam Chain tensioner, you will see a box with a set of four small metal brake lines coming out of the top.
• You can also check your brake lines - start at the brake lever, and trace the full length of the brake line - if it enters a strange box behind the engine, you have ABS.

• ABS (Anti-Lock braking) is a safety device. It allows the rider to squeeze the brakes as hard as they like without risk of the wheels locking. A locked wheel has no effective grip with a smooth road surface and as such gives no aid to balance, control or braking. A locked wheel will try to pass a turning one. A good demonstration is to roll a toy car down a sloped table at a slight angle. Repeat using putty to lock the front or rear wheels. ABS is about control in emergencies.
• ABS is not fool proof, it is set for a specific surface usually with the Mu (grip) level of iced tarmac. Put it on another surface and you start to loose efficiency until on gravel or snow ABS in its basic form is less efficient than locked wheels. Plus, a number of ABS failures like sensor chatter can only be detected after the system starts to cycle. If you can't complete the non-ABS stop you are in trouble.
• ABS braking is different to non-ABS. Non-ABS you feed the pressure and feel for the deep slip, releasing the pressure when you need to steer or when you get lock. ABS you just squeeze as hard as possible and leave the system to do its job. You ignore the brake feel.
• ABS is a safety device not an aid to performance. Think of the ABS like a cars air bag. If it activates, something is wrong. You cannot beat the laws of physics, break that law and you don't just get a ticket.
• I would pay for ABS if available, but I would also buy a non-ABS bike if I preferred another model and it was not available. Bike ABS is pretty crude in the scheme of things, but if it saves your life, someone else's life or even the machine, its worth it.
• Dakar ABS. The only boosted motorcycle system is on the K1200LT. The rest of the BMW systems are variations on the original system going back to the K100 police models. They all use an electric solenoid/pump system for the fluid recirculation back to the ABS modulator. All the brake force is produced by the rider but is modified by the hydraulics. The reason for the light feel is the larger master cylinder. The ABS means the designers can worry less about control feel as if the operator over does it, the ABS will limit the brake force to the maximum the road can take.

• ABS lengthens the theoretical stopping distance as it lets the brakes off when the wheel approaches lock. However, a rider faced with a real surface is unlikely to find the optimum brake force at the first attempt (the one that counts) and will never dare use the front brake (the most effective) enough because of the fall down risk associated with a locked front wheel. ABS used correctly therefore gives shorter real life emergency stops. ABS is required to meet 75% of the theoretical deceleration at the first attempt under EC directives. Most vehicles achieve 95% plus or beat the theoretical (proving the theoretical search using valves able to adjust brake pressure by 0.1 bar was not done to its full conclusion).

• Off road, a wheel in deeper slip (nearer to locking) produces a small pile of particles (snow, gravel, dirt etc.) ahead of the wheel. This gives improved braking. This is why ABS has the off road/off switch. This should only be used on loose surfaces, not ice.

• The ABS warning light sequence includes different flash sequences for different errors. These are known only to BMW (at present). The simple rule is, if the light is on you have full non-ABS braking, but may not have ABS. When the ignition is keyed, the ABS will test its components (you will hear clicks etc. as the modulators fire) and should reset if disturbed by a minor fault. If all is well the ABS light goes out. ABS cannot test its sensors fully until above 15kph. Below this speed you may not have ABS. Most systems do work down to about 7kph. The light will not come on again if both wheels decelerate in a normal way. Stoppies or wheelies may be logged as ABS faults and bring the light on.
• Flashing at a frequency of once per four seconds indicates the ABS has been switched off by the user. You need to turn the ignition off and back on in order to re-enable ABS.

• ABS is sensitive to battery voltages as it needs to differentiate between positive and negatives in its software to count the sensor wheel teeth against time. If the voltage is too low, the ABS lights flash alternately. It is OK to ride with care in this condition, but you do not have ABS. The first check on a failed ABS system is the supply voltage.
• Wheels sensors and sensor rings are external and are prone to damage during wheel removal. Off road use may cause damage if dirt forces the sensor away from the sensor wheel.
• On board radios or microwave phones may cause the ABS to detect a fault and shut down. The system should reset itself when the source of interference is removed.
• If you insist on using the full potential of the ABS and use the available stopping power, the disks and pads will wear faster.

• Riding with ABS is no different to non-ABS. You should not rely on ABS to save you from poor riding. Some ABS faults can only be detected when the ABS cycles. At this point you are in trouble. When ABS cycles, the controls may transmit some of the modulations into the controls. This is normal and the rider should continue with a steady squeeze/push on the controls.
• ABS activation may cause the brake pedal or lever to pulse, this is normal, but will only occur under harsh braking on low grip surfaces. Peoples first ABS stop can be worrying. There have been a number of incidents with Landrovers in the late 80's when people felt the ABS pulse and stopped pushing the pedal. The wheels don't lock if you do this, but its generally unhealthy.

• by Art #884, Pelle, Andy#982
• Turn Key on (Running or not)
• Wait for lights to go out
• Press and Hold ABS button, center of bars, until red ABS light starts blinking (approx. 3-5 seconds).
• Red light blinks until it is reactivated.
• To reactivate, turn bike off then back on, reactivation takes place automatically.

  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.

• The ABS on the F650GS seems to cycles so slowly that it make it very tough in the dirt. Instead of anti-lock you get lock roll lock, in a kind of bucking feeling. Kari from CalBMW mentioned that he uses the ABS on the R*GS when riding on dirt roads as it has a MUCH higher cycle time. He didn't use ABS while riding a Hollister hills this weekend... (but he was on a OLD R80RT (I think... I remember him telling me it didn't start life as a GS) cum R100GS. PQBon.
• Particularly in slow, technical riding you'll want complete control over your brakes, so shut off the ABS. if you're flying down a long graded dirt road, there's no reason not to use ABS. Mark #403
• Although I am not a technical person, I believe that under certain conditions, when braking on loose material, the ABS can be fooled when material builds up under the rear wheel. So it is not just a matter of more control without ABS. It involves ABS functioning improperly under certain off-road conditions. Technical experts: is this generally correct? If so, how does it work? If not, what is the scoop Don #783
• When skidding, the build-up of dirt in front of the tire can help slow down the vehicle (I learned this about cars, but assume it translates to bikes also). with ABS, you never get that because the wheel keeps turning. Mark #403
• Most of this stuff was covered in the prior (very lengthy) discussions on ABS use vs. non-ABS use. You switch off ABS in dirt because that's simply not where you're supposed to use it. The design specification for ABS are for paved road surfaces compromised by surface irregularities/contamination. When you ride off-road one of the skills that you're supposed to learn is really how your brakes work and how much they can really stop the bike. You're supposed to develop a feel for the brakes such as to be able to do threshold braking. And you'll quickly learn that 100% of your stopping power is really from the front wheel and that the back brake is mostly for directional or attitude control. The human brain is a much better computer with thousands of years of evolution vs. anything that BMW/Bosch have developed in the system. You as the pilot should continue to refine this developed system and trust it instead of handing off responsibility to an inferior system. It really has nothing to do with sliding the bike but has to do with your ability to stop the bike on all different kinds of surfaces according to your inputs. At one time you might want maximum over-braking then to back off only a little bit - then to be back on max then off - you can do this manually but you can't do this with ABS. Riding off-road is a ballet between throttle, clutch, brake and weight shifting like no other in motorcycling except trials riding. You want to get hard on the front brake to pre-load the suspension such that you can loft the front wheel easier to clear an obstacle then grab some brake and do it - if you've got ABS on then the computer thinks that something is going wrong and tries to stop the wheel from locking - bad things happen when you can't slow down and get the front suspension compressed to help spring you over the obstacle and your front wheel goes in to the ditch or clanks off a rock sending you flying. Sure, ABS is a REAL safety feature here! When you're climbing a hill you're CLIMBING it (notice the emphasis) you're not really going to want to make a full stop up the hill when climbing. That's the last thing that you want to do. What you describe as cool no tarmac riding, a village back street does not really qualify as off-road. It might be an unpaved surface but that's city riding not off-road. Even given this if you know what your brakes do and how to really use them you can out-brake the ABS manually. Of course there are always situations like that donkey cart coming out of the side alley in front of you where neither ABS nor good manual braking will help you. These are the positional/situational problems where basic physics always wins. You can't have two objects occupy the same time and space at the same time without hard results. Also given objects travelling along a path at a certain velocity with given mass, inertia, and abilities to decelerate/manoeuvre will also lead to different results according to their control elements. Davidhpark, #711
• I know about ABS. It is my profession. I work with ABS day to day. I am a professional with practical experience of vehicle testing. ABS will outperform any rider no matter how skilled on any surface it is designed for in terms of stopping distance and control at the first attempt. Just to clarify, the surface the system is designed for, this will be the street, with ice or water on it, or any similar hard surface. The Human brain is amazing but it gets its information from feel not direct from the wheels. Perhaps Mr Park can tell us his percentage wheel slip while performing his feats of ABS beating braking or even the distances achieved? In a test environment with a known surface, it typically takes 10 or more attempts to get close enough to the ABS braking performance to do a legal comparison. ABS seems to lock and cycle slowly because it is maintaining a deep slip, it is holding the correct amount of braking. This is the area just before wheel lock where the wheel produces maximum braking. The wheel is actually turning much slower than the vehicle is travelling. Unlike the locked wheel it can be steered and provides gyroscopic forces to keep the bike upright. A locked wheel provides almost zero stopping power (see skiing and ice skating). Road ABS cannon handle loose surfaces such as dirt or ice because it uses a fixed rate of slip. This slip rate is incorrect for a surface where the pile of debris ahead of the wheel can be used to increase the contact area of the tyre and its general adhesion. In this case deeper slip makes more debris and lets the wheel make a trench to give better control. The simple solution is to turn the ABS off. Vehicles where control is more vital and weight is not an issue use either dual slip rate ABS (trucks have a switch that changes the ABS slip rate) or multi rate (e.g. Land Rover monitors gearbox for level of off road). The problem we have with the F650 ABS is peoples different riding requirements. The ABS is designed for wet roads. A small amount of dirt like sand blown onto a road or a hard dry dirt track acts like water on tarmac. The tyres can move the particles like they move water. Sand like on a beach gives the berm/wave effect so you want ABS switched off. Wet mud behaves both ways depending on the depth and consistency. Grass makes a big difference too even when mashed into the mud as it can either make a smooth surface (good ABS) or make the pile round the wheels stiffer (good non-ABS). The decision on when to switch off the ABS is down to the rider, who needs to know what is and is not off-road from the braking point of view. The BMW bike system is too basic to do this job itself, but there again bikers tend to be smarter than the average 4x4 driver. The only hard rule is to switch back on when you hit the tarmac if you want to get you money's worth out of the system. Andy Leeds UK #982
• To answer this question go riding in any loose surface conditions (hard pack does not really count). You will hate having the ABS engaged if you ride even moderately hard there. It actually makes the bike harder to control in my opinion. The ABS takes a lot of control away from you in low traction conditions. To ride successfully and perhaps safely off road one needs to master the modulation of both front and rear brakes up to and including full lock. Locking the wheels can be used to help steer the bike when throttle induced wheel spin is not appropriate. On larger GS bikes I would defer to others. With that much bike and possibly different ABS it might make sense on your basic hard pack dirt road. I think it has a lot to do with how you ride off road. Not all dirt riding is the same. Riding a dirt road that a passenger car could use is different than riding trails or desert at speed. ...and I could be full of cr*p too. Just my thoughts. BradG#1002

• by Andy Leeds UK #982
• Stoppies are theoretically possible but practically hard to do.
• You need to keep the rotational decel'n on the front and rear wheels matched within about 5% until the ABS cuts out at 5-7 kph. This way the ABS thinks you just slowed the whole machine as no wheel varies too much from the reference speed. There is a prize for anyone who can do this!
• Winding the front brake on while locking the rear hard just as it lifts could be the key. The system will be confused into thinking its the rear that locked not the front. It will then modulate the rear. Again there is a prize if you can do this without the ABS beating your reaction, allowing the rear to spin up and then deciding to modulate the front to match the reference speed.
• The conventional clutch and front brake stab will tell the ABS that the front did an impossibly quick decel'n and will result in immediate modulation

• PQbon states:

  • 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.

• Andy #982 replies:

  • 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.

• Please test your ABS in a controlled environment, and make sure you have appropriate protective gear on.
• The rear is very easy to activate. Simply press the rear brake lever very hard and it should activate.
• I can get mine to activate when I enter my garage--I have a painted floor. I've also been able to do it on side streets that have painted arrows on the road. RevJVegas #1906
• Wet grass. In a straight line. Slowly. Practice. Bryan, #179
• Just be sure it's LEVEL wet grass.

• No. During normal operation, the light will not come on even if the ABS system does engage.
• The ABS light will only come on in the following cases:
  • When you initially turn the key to the on position
  • When have turned the ABS off (light will flash once / 4 seconds)
  • When there is a fault

• 0.1 - 1.0 mm front and rear

• The ABS system is basically maintenance free. If it has problems the warning light will stay on when the bike is moving. Then, basic checks can identify the problem without recourse to the dealer.
• ABS senses the wheel speeds by inductive sensors. These are just a coil that a toothed wheel induces a voltage in. The frequency gives the wheels speed, the amplitude gives information about the condition of the toothed wheel. An ABS sensor can be checked simply by spinning the wheel and checking for an output voltage. A sensor that is open circuit is failed. If the airgap between the sensor and toothed wheel is too great the voltage will be low.
• Experience suggests the sensors will be OK at 0.1 to 0.7mm. I would not recommend resetting the sensor air gap if the system is working, as part of normal maintenance. I would suggest the gap is monitored. The air gap should be the same right around the toothed wheel.
  Damage to the teeth on the wheel will prevent the ABS working. Never lay the wheel with the ABS sensor ring face down. The sensor wheel needs to be free of chips, have no missing teeth and run out should be limited within the air gap specification. Worn wheel bearings may first come to light when the ABS detects runout or other chattery signals from the wheel.
• The ABS modulator is just a pair of electrical solenoids that allows brake fluid to circulate in a bypass to the master cylinder to brake calliper circuit, reducing pressure and releasing the brakes. Again this solenoid coil can be checked for continuity. At ignition on or when the bike moves off it should self test. This will be heard by the rider as a click or slight screech/clunk noise. The solenoid is the two can shaped things with the ABS ECU bolted on the back. It should be under the faux tank.
• The ECU is not very bright and only knows about battery voltage, warning light condition, wheel speeds and modulator coils. BMW diagnostics only tell them what the ECU thinks is the problem. If in doubt get BMW to clear the memory, then test ride the bike and recheck. In effect the ECU only knows what pin of the ECU the problem is on. ABS is not rocket science, but the ECU modulator assembly is too expensive to change on the off chance. Take care that dealers check out other possibilities before blaming the electronics.
• Bleeding an ABS bike is no different to non-ABS, but may take longer due to the additional piping. The ABS should never be powered up when there is no fluid in a circuit as the modulators may require the fluid for internal lubrication. This may not be 100% correct. Refer ABS & Brake Bleeding. Can I still do it myself?
• The sensors can be changed at home with no diagnostic equipment if the power is off. The ECU and modulator block can likewise be changed as a unit. The master cylinder/reservoirs and callipers can be changed in the same way as a non-ABS bike.
• Check the Fuel Injection FAQ for information on the GS911. You can use this device to communicate with the ABSN, and check for fault codes.

• ABS can be upset by changed wheel sizes. The system needs to know how fast the bike is going to work out if a wheel is going into slip. If a wheel or tyre is changed the wheel may spin faster or slower for a given vehicle speed. This will effect the systems knowledge of what is going on around it. The BMW system is not particularly sensitive to this so there should be no problems changing tyres.
• A few people have reported no problems changing from a 19" GS front wheel to a 21" front wheel.
• Radios/mobile phones may give trouble if too close. Nothing should share the power supply to the ABS ECU.

• The core difference between bikes with and without ABS are the following components:
  • Wiring Harness - This will differ based on other things such as Hazard Flashers. See the online parts fiches listed in the Parts and Fiches FAQ.
  • ABS Unit Itself
  • Brake lines - You will need to add or remove all the additional brake lines for the ABS system
  • Front ABS sensor
• Alternatively just remove the fuse for the ABS / disconnect the unit for a cheep option to remove the unit.
• seh750 managed to remove ABS from their bike. After removing the ABS unit itself, they found the speedo did not function. The solution: According to the wiring diagram, the speedo signal goes straight from the ABS to the dash and does not go to the BMS. I figured it out, either my bike is different or the wiring diagram I looked at is different, but swapping pin 1 and pin 3 solved the problem..... Pin 1 and 3 on the ABS connector. Pin 1 (white with black stripe) connects to pin 24 (yellow) and pin 3 (white with brown? stripe) connects to brown/ground (don't recall the pin number). - So yes, you can remove the full ABS system, and using seh750's suggestion, still have the speedo working.
• Refitting ABS is not an option. First you need a new brake system and new wheels. That's more than 1500 Euros to start with. Next you need a "competent" person to write you a report saying its fitted and working to the exact same spec as what BMW fit OE. If you are lucky your local authorities will then accept the registration. If not they will ask to see the type approval certificate, BMW will refuse to give you a copy and you have a worthless bike. Andy Leeds UK #982

• For Normal bikes without ABS see the Brake Maintenance FAQ
• The jury is still out over bleeding the ABS yourself. Different people take different sides to the story. The answers provided here are a summary of the points raised for/against bleeding the ABS yourself. Please make up your own mind based on these arguments. Asking for more opinions in the Forums will receive mostly the same sort of answers.
• According to the Shop Manual, you need a piece of BMW equipment called a BMW MoDiTeC to do it right. Bobcatou
  
• Arguments Generally Against Bleeding ABS Yourself:
  • Some people find they can not get all the air out of the ABS system if they bleed it themselves.
  • Some people have reported after bleeding ABS brakes themselves, then having the ABS bleed using the MoDiTec, braking performance is much improved.
  • You can not bleed the unit without MoDiTeC or some other means to open the valves in that unit to allow the fluid to circulate.
  • In the repair manual with date 02/00, on pages 34.5, 34.8, 34.11, 34.12, 34.17 (two times on same page) and 34.19 the following text is highlighted: Important: If the vehicle is equipped with ABS, the brake system has to be bled using the BMW MoDiTeC, and the Control Units, Toolbox ABS, routine; this procedure is supplementary to that described in the Repair Manual. If the BMW MoDiTeC is not used there is a danger of residual air remaining in the control circuits of the ABS system.
  • On ABSN equipped GS's The ABS functions by releasing the brake pressure thru electric valves when the ABS is applies. These valves hold fluid inside them and when bleeding the brakes to "change the fluid" there will always be old fluid held in this system. If you want to change all the fluid, and you should, after bleeding the brake in a conventional manner, You must use MoDiTeC to release these valves and flush new fluid into to ABS unit and old fluid out. You must then re-bleed the brakes.
• Arguments Generally For Bleeding ABS Yourself:
  • Both conventional and ABS braking systems are bled in similar fashion. Certain ABS systems require the use of a bi-directional scan tool to cycle internal solenoids to purge the system of air.
  • Many people have reported bleeding their ABS brakes with no problems.
  • Keep in mind the brake lines are much longer, so it may take a little longer than normal.
  • The technique used is the same as bleeding any brake system. Some people suggest bleeding the brakes once, then take the bike out for a ride and force the ABS to activate, then bleed the brakes a second time.

• No the light flashes as a safety so you have a reminder you have the ABS off. You can not turn that light off. KiwiDakar (02)

• http://www.ibmwr.org/prodreview/abstests.html

• 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."
  from: http://www.webbikeworld.com/Motorcycle-Safety/braking-tips.htm

• 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.