Motorbike ABS.

[Sir Trev]

Originally Posted by GavinD

with correct tyre pressures etc you can brake to the point of feeling the loss of traction - something that ABS takes away and therefore you can never find the true limit of the brakes.

Trouble is when the ignorant pedestrian on the phone walks out from behind the parked van without looking, five feet in front of you, will anyone have the time to find their braking limits? I agree with your point entirely, and it's what the journos found when they reviewed the first bikes with ABS, but the technology is a bit better now and sometimes the OMG! reaction takes over and you just grab everything you've got (brake wise). In that situation ABS would be a help.

If only we could get ABS with ESP we could have the best of both worlds!

imo get it on bikes the sooner the better! on cars it saves lives from people that drive too fast. It will do the same for bikes.

Yea you can get cars (lets take a tvr) that have no abs. however you stick somone in a tvr that drives like a nutter and they will kill themselves as they lockup and spin into a tree.same goes for bikes. Yea we could train everyone but looking at the standard of driving todayt hat aint going to happen. Get it on all bikes and get it on fast imo

[SoulKiss]

Originally Posted by RatchetJob

This graph shows the hydraulic pressure in an ABS system when ABS is in operation



The red line is the speed that the controller thinks the bike is travelling at calculated using an average of lets say the rear and front wheel speed.

If the front wheel speed drops significantly below the calculated speed (see the dips in the blue line) the controller reduces the pressure in the braking system via the modulator (see the corresponding dip in the black line). This drop in pressure will cause the front wheel speed to increase again. When the wheel speed approaches the actual speed again the controller increases the brake pressure again until the wheel speed starts to dip again.

As you can see the brake force does not reduce to 0%, what the controller tries to do is balance the force so that the wheel speed stays close to the actual vehicle speed.

Makes sense - however where is that graph from - there are ABS systems and then there are ABS system after all......

I would argue differences in how Kwak/Honda/BMW impliment it (based on cost to add to the bike if nothing else)

Like the GS I rode - I'd like the choice.

Take it off on dry nice days, put it on when its wet/just after a light summer shower/cold or if I'm just not feeling that I'm riding as best i could be - be it a little tired maybe.

Lets use a rear brake example as it may be easier to explain (as you're not as likely to fall off)

If you lock your rear wheel you have to release then reengage. If you don't then the rear wheel locks, you don't forwards but it doesn't slow down particularly slowly

With ABS you keep your brake on and it pulses on and off. The rear wheel shouldn't lock properly, it will lock and then release many times in a short amount of time, which means it will have better traction that a locked wheel and then you slow down quicker.

Isn't that the gist of it? The example probably works better in the wet than the dry as well....


EDIT - forgot to add, it can't fool the laws of physics, just like all traction control, brake force distribution and stability control systems, much as some people would like to think (no one in particular, just joe public)

Have any of you lot ridden ABS? Ever driven a car with ABS??? Does the abs in your car prevent you from braking as fast as possible, or does it kick in when the wheels lookse braking traction?????


Frankly, i can push my brakes VERY hard. Its a heavy bike and small brakes, but i had the disks smoking the other day, abs never kicked in once........

It does kick in sometimes, if you go over a hill brow whilst on the brakes, it fools the system and it kicks in and pushes your fingers out. Also, if your braking in the wet, over a drain, it kicks in which can be a little scarey if you've timed your braking to the point....

But no, ABS does not effect your brakes at all unless the wheels rotate differently. I've never had the ABS kick in when im pushing the brakes, definatly not when im really braking hard. The biggest restraint is the pads, not the ABS....

ABS is a good thing imo, and sure you can't skid the rear wheel, but it aids control of the braking, esp if the back end steps round on hard braking, as it stops it locking up and going out of control.

And as some have said, if you had abs on your SV's and hit the brake too hard (hence sending the front underneath you), you won't crash. It saved me in london quite a few times.

Originally Posted by benp1

If you lock your rear wheel you have to release then reengage. .

But you don't have to fully disengage - just ease off! I have had to do this in one of those heat of the moment times -you don't just let go when it locks!

[dizzyblonde]

dunno, think I'll stick with the old faashioned way. Too complicated if you ask me, I like simple. Simples

That graph is just a basic illustration of ABS operation. You're right that other manufacturers will implement their systems differently.

Most ABS systems work using a modulator, what this does is release hydraulic pressure by making the volume of the system larger i.e. moving a plunger connected to the system out. The system can be brought back to its original size again by pushing the plunger back in - raising the pressure again.

Rather than have the system move the plunger by preset distances to reduce the pressure by a given amount (mechanically complex) the manufacturers tend to just allow it to move completely out or completely in. They vary the pressure in the system by changing the frequency and duty cycle of the pulses (mechanically simple).

The difference in the systems will be in the range of frequencies and duty cycles they can produce not really in their operation.

[flymo]

I think ABS is a great innovation on a motorcycle. At the end of the day if your wheel is not rotating, or at least not fast enough then it isnt producing grip, cannot influence your direction (which is a problem with a front wheel!) and cannot slow you down using your brakes. Hence ABS.

ABS will improve over time, it has already come on leaps and bounds, mostly due to the performance and speed of the sensor electronics. Same as traction control in most aspects.

The argument in racing circles is not that its no good but that its actually too good and takes away the need for rider skill usually at high expense for the very latest incarnations.

If you have felt ABS activating then its saved you from a lock up that you would certainly have had it not been there. As far as complexity goes, all you have to remember is to keep pressure applied to the lever, pretty simple really.