I carry a small messenger bag even on a normal ride (aka not commuting). I keep pretty much everything I could possibly need in there: chain breaker, spare links, tube, money, huge multi-tool, first aid kit, cresecent wrench, cell phone, electrical tape. Worse comes to worse and I can't fix it, I could call my shop or even another bike shop and they would send someone.......got to keep it real like that.