Kemo has you covered, if the tires are beyond 4 years probably getting close, also inspect tires in strong light, any evidence of "age" cracking or tread wear to the tread wear indicators (raised horizontal bars used to guage 1/32 overall wear) should guide you as well.
Rubber compound is natural with some petroleum based products which degrade when exposed to heat, ozone (garage fired appliances), sun, and on-road contaminants. That tire patch contact area is about the size of your palm, which elongates when the tire gets leaned over...and if you take off wheels and buy tires from metric dealer, they mount and balance 'em for free...though dealer shop labor being $75 is a choice based on your confidence level.