ERL: Your tires are probably old enough to vote. As tires get old, they get hard and don't follow the irregularities in the road as well. Your tires may not show much tread wear or checking, but if they don't bounce, they will make your car ride like a log truck. ALSO, don't try to use a larger tire on your Darrin. Look at the clearance between the front tires - especially the driver's side - and the foot boxes in the fiberglass tub. The Darrin I was first shown this on didn't have enough clearance to slip my index finger between the tire and fiberglass.