2000 R1150GS ABS brakes

[The Fabricator]

I have posted before regarding the ABS performance for my GS.

The front wheel has locked up a few times on dirt and I crashed.

I understand the ABS doesn't work below 5mph, which is what happened.

Now I am wondering if I could lower the cut-off speed with a tone ring with more cut-outs.

Opinions?

[dirtrider]

4 hours ago, The Fabricator said:

I have posted before regarding the ABS performance for my GS.

The front wheel has locked up a few times on dirt and I crashed.

I understand the ABS doesn't work below 5mph, which is what happened.

Now I am wondering if I could lower the cut-off speed with a tone ring with more cut-outs.

Opinions?

Morning Fabricator

 

My opinion is: don't mess with it.

 

Unlike a 4 wheeled vehicle a motorcycle depends on it's spinning wheels to stabilize & stay upright.

 

On an automobile the ABS system can take the wheel spin speed to just above lock-up or even into lock-up with no issues.  On a motorcycle (single track vehicle) the ABS system needs to still allow the wheels to spin slightly or it kind of defeats the idea of having ABS.

 

The the other thing to (really) worry about is if either wheel is allowed to come too close to lock up is the re-spin-up on a very slippery surface.  If the ABS system brings the wheel speed too low during an ABS event  on a very slippery surface there might not be enough tire traction remaining to restore the wheel spin-up quick enough to prevent loss of motorcycle control. 

 

There also has to be a low speed cut-off that allows the wheels to actually stop spinning, if it didn't have this then you could never actually bring the vehicle to a complete stop using the brakes as the ABS system would just allow them to keep on spinning thinking they are locking up.  

 

There is one other thing to consider, on the BMW I-ABS system the ABS computer looks at the front & rear spin-down rates vs front & rear wheel braking pressures then automatically adjusts the front/rear braking bias to balance the braking  between the front & rear. If you alter the speed input vs actual you might change how the ABS system trims this braking balance at speed.

 

Bottom line: you might be able to mess with the low speed ABS braking by changing the tone ring input pulses but more than likely that would be at the loss of high speed ABS braking control on slippery surfaces. 

 

Or put another way, would you rather have the motorcycle go down (usually low-side)  somewhat softly at a very a low speed due to too much brake apply or have it lose wheel spin-up at high speeds then violently toss you off high-side at higher speeds?

 

The very low speed braking on the BMW 1150 I-ABS (wizzy system) is not the best (not even close) but that is typically not due to ABS but more due to the darn power servos making low speed brake modulation a pain to deal with for some riders. 

 

A number of 1150 riders just remove the ABS system as that brings back great feeling & smooth modulating braking at lower speeds but that definitely requires experienced braking by the rider at higher speeds on slippery surfaces as there is then no ABS (save your butt) to protect you during higher speed slippery surface braking events. 

 

 

 

 

[The Fabricator]

Thanks.

[Michaelr11]

18 hours ago, The Fabricator said:

front wheel has locked up a few times on dirt and I crashed.

I understand the ABS doesn't work below 5mph, which is what happened.

I can’t compete with the details of DR’s response, but I wonder if you are using OEM BMW brake pads. If the brake pads in use had more grab than the original pads wouldn’t that fool the ABS computer and let it lock up the wheel?

 

[dirtrider]

11 hours ago, Michaelr11 said:

I can’t compete with the details of DR’s response, but I wonder if you are using OEM BMW brake pads. If the brake pads in use had more grab than the original pads wouldn’t that fool the ABS computer and let it lock up the wheel?

 

Morning   Michaelr11

 

Grabby brake pads can effect the brake apply feel but at lower speeds but the ABS should still prevent wheel lock-up. At higher speeds on a very slick surface then overly aggressive brake pads can make it difficult for the ABS system to modulate the braking correctly.  

 

On the BMW 1150 I-ABS system it's that walking speed braking that is sometimes difficult as it is slow enough for the ABS not to  function but fast enough to cause problems under braking with the handlebars turned. Some of the 1150 servo systems  can be pretty abrupt & grabby at very low speeds.