While getting ready to instruct a Motorcycle Ohio class on the Hilltop last Saturday, I low-sided one of the training bikes while traveling 12 to 15 miles per hour. This accident resulted in three broken ribs and two suspected fractured ribs. The factors involved in this accident include, cold tires, cold pavement, new tires and lean angle. While staging the bikes for class, I failed to notice some of the bikes had new front tires. My assumption that the tires were seasoned is costing me six to eight weeks of riding and instruction time. Don't assume.