Linked ABS

[GAPS]

Will front and rear brakes be cycled if one shows slip? Or do the act independent of one another? I would guess they must be seperate but the linking of the system has me wondering.

Step on rear brake, rear tire skids, ABS cycles, linked brakes release both front and rear? Only rear?

In the car world you see three and four channel systems. What does a linked ABS bike have?

 

[charismaticmegafauna]

GAPS: (nice Laverda) Since there's been no replies, yet -- I'll take a stab at it. I'm certainly no ABS expert; but, I think?, only the wheel that's not in conformity (speed-wise) will be artificially controlled. That's why there's a computer and manifold and extra tubing, etc. -- the more assistance = the more complex.

btw, in the Mar.'06 issue of Motorcyclist (on page 37), in a story that looks to be taken verbatum from a BMW press release, it says, "Front and rear brakes aren't linked in the new two-channel system..." and "....you can switch the ABS off completely for hardcore riding or track days." Whats up with that? Is it better when it's not there (switched off)?

Gaps: I know it's not nice to answer a question with a question (the last part) -- but, I think there'll be some FJR owners who do have answers here?

 

[GAPS]

CMF, I read the BMW lingo this way...., as you hand over more control to the ABS system the intent of the riders inputs are diluted. ABS becomes a liability to a rider trying to lower lap times as it does not allow the level of control needed under those circumstances.

I just wonder about the 06 FJR, of course linked ABS is the norm on a car with 4 channel systems controling each wheel seperate.

On a bike with standard ABS brakes I figure you must have a 2 channel system so the ABS can sense slip at each wheel. This would allow only one wheel to be cycled when slip is evident to the computer.

On the other hand I imagine you could design a single channel system for a bike with linked ABS. One where both wheels are released when slip is encountered.

Im sure there are holes in what I say here, I just dont know where.

THANKS on the Laverda, it sure was purdy, eh?

 

[GAPS]

Also, the term 'channels', what exactly does that mean in ABS language?

Does the # of channels equal the # of wheels which can be controlled independent of one another?.....this is what I have been thinking, not sure though.

 

[ionbeam]

Does the # of channels equal the # of wheels which can be controlled independent of one another?.....

[SIZE=14pt]BINGO![/SIZE] The operative word is INDEPENDENT. My wife's truck has a three channel system -- one for each of the front wheels (2 channels total) and one channel for both the rear wheels combined. If either rear wheel slips they both get the ABS treatment together. The front wheels will be ABSed independently of each other and independently of the rear wheels.

ABS Actuator - The work horse of the ABS system, it's the piece that actually releases pressure in the ABS channel to modulate the brakes.

ABS Channel - The channel is the hydraulic line(s) from the ABS actuator to the wheel(s). ABS channel can consist of 1 or 2 wheels (2 wheels = my wife's truck rear wheels) that will pulse/modulate when the ABS actuator performs its work.

ABS Sensor - Measures the speed of a wheel. Consists of gear-shaped sensor rotor and a sensor element. The element contains a bar magnet around which a coil is wound. The sensor is installed on the back side of the brake rotor. Sine-wave current is generated by the sensor as the wheel rotates. The frequency and voltage increase(s) as the rotating speed increases.

ABS Pulse or modulation - When the ABS Actuator engages and pulses/modulates the brake pressure being applied to the ABS channel. This is the method by which the system actually works. When the brakes pulse, they are prevented from locking because they rotate for a split second.

 

[charismaticmegafauna]

Ionbeam, thanks for the help. Is the ABS actuator a valve (like a solenoid operated hydraulic valve) or is there a motor and pump involved, too? I know on early BMW m/c systems they had these great big things (like auto starter motors) front & rear for ABS. They looked like "pumps" of some kind? Are there different "patents" for actuators?

And, (back to the beginning) how does linked or un-linked figure into this? I'm guessing it's a non-issue (everything happens at the particular caliper)? Just a matter of more (linked) or less (non-linked) plumbing?

 

[ionbeam]

I don't know for sure if the '06 linked brake system will be one channel or two but I would speculate that it is 99.99% likely to be two channel. The front brake produces ~85% of braking force under normal driving. The rear brake locks very easy because it does not benefit from weight transfer during deceleration. Why take brake force away from the front wheel when the back locks? :shock:

The FJR ABS system (standard, not '06 non linked) uses an electrical motor to drive a pump. The front and rear brakes each have a solenoid. The major ABS unit under the seat has a buffer chamber, flow control valve, pump, ABS motor, spool for flow control, 2 ports (2 channel) and pressure orifices.

 

[FJRski]

This is an item of interest to me, as I am waiting for an '06 (ordered in October), and one thing I really liked about the '05 model was that the brakes were NOT linked. As I understand it, this would make it a 2 channel system, because the ABS would have to actuate independently. Sometimes you can tell by looking at the ports in the actuator. But the big item of concern for me is whether the linked system removes an element of rider control. I want to be able to control how much brake I apply to each wheel. I like the thought of having ABS, we have tons of wet leaves on the roads here in PA, I'm just not sure I like the linked part.

 

[Constant Mesh]

The hand brake has no effect on rear braking -- no linkage. The foot brake actuates the rear caliper plus 1/4 of the front braking system (2 of the four pistons on one of the front discs).

My concern would be the change in front braking. The hand brake will control only 6 of the 8 front pistons as compared to controlling all 8 pistons on the '05 and earlier models. Will you have to use more brake lever force to get the desired front braking? More pressure applied to fewer square inches of front brake pads?

 

[GAPS]

Constant Mesh, I believe you are mistaken. The 06 'front brake' is linked to the rear caliper as I recall from Yamaha propaganda.

 

[GAPS]

Hellyeah!! My mistake, the front brake lever is not linked to the rear calipers! After rereading Yamahas brochure I see that only the rear brake pedal operates in linked manner. Sorry Constant Mesh, and thanks for opening my eyes to that.