Charles:
The motorcycle cable is more substantial than the car cable - the outer covering is made of a different kind of rubber, meant to be more resistant to the elements, abrasion, UV, and grease and oil, as well as retaining flexibility during cold weather riding.
But, the gauge of the wires inside the motorcycle cord is identical to the those in the car cord. You would not want the individual wires to be any bigger - the voltages carried are small, and in the case of some of them, very low amperage - so any increase in wire gauge would cause transmission problems and an increase in power consumption.
I used a SP III cable for 70,000 km on my moto before changing it out to install a SP 2650 cable - had no problems with wire gauge size at all. If you are concerned about conductivity and making good connections, strip off more insulation than you need, double the bare wire back on itself about 3 times, and tin it with a soldering iron. This will give you something more substantial to attach to your electrical connector. But, be careful that you don't allow solder to wick up the wire (beyond the part you have stripped), otherwise, this increases the possibility that the wire may break later on due to fatigue, vibration, or impact.
If you are connecting the Garmin cable to an auxiliary bus bar on your moto, and want a more substantial wire gauge for the connection point, just splice the end of the Garmin wire to a short (few inches) section of heavier gauge wire, then use the heavier gauge wire for the connection point. But, keep the length of the heavier gauge wire as short as practically possible.
PanEuropean
