I bought an '06 Wee a year and a half ago. The original owner had hardly ridden it; it sat in a garage for years. After changing the oil and the gas, it ran pretty well. The tires work pretty well, too, but I have read about the effects of ozone on rubber, and I am wondering if I should replace them. They don't look cracked (they were, after all, stored in a garage), and the min. tread left is 4mm. Altogether, the bike now has been ridden about 6,800 miles. But the tires are coming up on ten years old. Is it time to replace them?