by DarrenR on Wed Dec 21, 2016 11:14 am
The Bosch ABS measures rotational speed of the wheel, not the surface speed of the tyre. It internally converts the rotational speed into surface speed with a circumference figure programmed into it, and then it reports this surface speed on CAN.
We read this wheel surface speed on CAN, but what we need to know is the rotational speed so we can then set our own wheel circumference figure and you can correct the wheel speed in the M1 to your wheels if they change size.
The Wheel Circumference figure in the Bosch ABS module is only there to translate the wheel speed reported by the bosch unit into a rotational speed and you should only ever need to change this if you change the wheel circumference in the bosch unit itself.
Darren.
Darren Reynolds
MoTeC Research Centre - Melbourne, Australia.