BMW K bikes (Bricks)

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1Back to top Go down   ABS brain teaser Empty ABS brain teaser Thu May 19, 2011 8:46 pm


Life time member
Life time member
Some of you may have been following the thread 'Are radials worth the effort?'.
I am looking at the feasibility of fitting the rear wheel and front end from a K1100RS to my '89 K100LT in order to fit radial tyres for handling and the improved four pot brakes.
I have all of the parts now but one problem has arisen and this is were I'm looking for feedback to an idea I have had. The problem is that I may have to remove the ABS to make the changes as the 16v engines used a slightly different system.
The rear wheel is no problem as the same components for braking are used. So its almost a straight bolt in.
One of the components of the 8v ABS system on the front wheel is the sensor ring. This consists of a metal ring with a series of sections cut around the edge and is mounted behind the right disc.There is a magnetic pick up fixed close to the ring which tells when the wheel is about to lock and releases the pressure before it does so.
The 16v uses a similar idea but the sensor ring is mounted 'flat', on the same plane as the disc.
At first I thought they would be incompatible and the ABS would have to come off.
But after a bit of thought I measured both sensor rings and found that both have exactly 100 notches and the 8v is 19cm and the 16v is 18cm in diameter.
My idea is this. If I changed the front end over and plugged the 16v sensor into where the 8v sensor was plugged in, would the ABS still work?
The only other change to the braking system would be using the 16v master cylinder with the larger piston and I don't think that would effect the ABS system.
I can't see why this wouldn't work but would like to hear other opinions.

2Back to top Go down   ABS brain teaser Empty Re: ABS brain teaser Thu May 19, 2011 9:52 pm

Crazy Frog

Crazy Frog
I don't know anything about ABS (I don't have them on the 85 rt) . From my experience in robotic and step motors, sensors only count the pulses to translate it into linear displacement. ABS systems certainly use a second parameter which is time between 2 pulses (maybe in ms).
As you have the same amount of notches on both brakes, the only difference would be the time that it takes to travel between 2 notches.
The ABS computer may first calibrate itself and COULD compensate for the difference of diameter of the ring.
It may work but everything has to be tested first.
This is my opinion, and I could be wrong!

Why did I posted this, I don't have experience in the subject Embarassed

ABS brain teaser Frog15ABS brain teaser Logo2101986 k75, 1985 K100rt, 1985 K100rt/EML GT2 sidecar, 1999 K1200lt/Hannigan Astro Sport sidecar.

3Back to top Go down   ABS brain teaser Empty Re: ABS brain teaser Thu May 19, 2011 10:07 pm

RicK G

RicK G
I actually came to the same conclusion but never got far enough to find out. I have the computers of both in front of me and the part No is different
K100LT 8/1990:
BMW No 1 459 699 E9012.A
HELLA No 5SD 005 583-00

K1100LT 1/1993:
BMW No 1 459 924 E9088.B
HELLA No 5SD 005 583-01

So there is a difference in the computers but if it would cause one to work and the other not to work I can't say.
The case is different as to how it mounts on the bike but come to think neither mount through the tabs that are different.

Maybe the guy in Japan that fixes them will be able to tell us.

I am now considering putting it on the K75 as well if it is as good as I expect.

I take no responsibility for this bit but I would go ahead and put it together and see if it works after all it is not like you will run out of brakes because of doing it.


Last edited by K Freak on Thu May 19, 2011 10:11 pm; edited 1 time in total (Reason for editing : More garbage)


4Back to top Go down   ABS brain teaser Empty Re: ABS brain teaser Fri May 20, 2011 8:22 am


active member
active member
ABS 1 sensors are interchangable if that helps...


5Back to top Go down   ABS brain teaser Empty Re: ABS brain teaser Sat May 21, 2011 8:20 pm


Life time member
Life time member
Been thinking about this and decided that I will give it a go.
Both systems use the same principle and as Bert points out, the only difference would be the time between the notches.
Using a rough calculation I reckon that the K1100 ring will be about 5% slower than the K100 item. I don't think it will cause any real problems. After all, the software is now about 25 years old.
Going to get the parts ready and have them ready in large pieces for a weekend swap in a few weeks.
Going for a trip around Southern Ireland week after next for a few days and don't want to take a chance of getting stuck and not having a bike.

6Back to top Go down   ABS brain teaser Empty Re: ABS brain teaser Sun May 22, 2011 3:36 am


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Life time member

Best of luck John, let us all know how it goes and enjoy your trip around Southern Ireland look forward to some pics.



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