Probably the biggest spare that I have (on motorcycles) is that we both ride.
I used to carry just metric, then I sometimes travel with both a Honda and an HD... So my tool box now includes
8, 10, 12, 14, 17 and 19, and then 1/4, 3/8 1/2 (which works for 13), 9/16, 5/8, and 3/4, then metric and SAE Allen, and various screw drivers.... BTW the Japanese Phillips is different than the American Phillips, tire irons, and when with a sidecar a scissor jack and a 12" adjustable (crescent) wrench. And yes a plug in air pump
