I would definitely change those tires. Tires go bad even if there is plenty of tread, they have a date stamp on the side that shows when they were manufactured. It's four numbers, the first two numbers are the week (out of 52) and the second two numbers are the year. Shows the week of what year they were manufactured, I reccommend changing every 3 years although I think you're supposed to be able to get by upto 5 years. Either way, you're over due.