E30 Zone

I have done a search but not found what I am looking for. The fuse box listing doesn't seem to be of any use for this either.

I want wire in a switch so that i can turn the ABS on and off on my 1990 325i sport, on for raod use and off for track use to try and save my pads.

Has anyone done this or got any suggestions on how to go about it? I was thinking that if I could find the fuse or relay I could just break the circuit with a switch? Or if I just break the circuit to the earthing point would that be an easier way to do it and still be safe? Any help appreciated.

Power feed for the ABS system is a red/white or red/yellow wire from the main DME relay through pin 20 of the C101 connector which then splits to the ABS ECU and the ABS pump.
Interupting this feed will kill the ABS

Cheers, I'll let you know how I get on.