Tires may be the only part of a vehicle that physically meets the road, but your shock absorbers are next in line. Working with the suspension springs, they absorb shocks from bumps and cracks in the road, while simultaneously controlling bounce and body roll.
Depending on what vehicle you drive and your driving habits, shocks tend to wear out after about 60-90K miles. A completely blown shock absorber is very easy to diagnose; your car will have to ride only on the suspension springs, which causes excessive bouncing. If you push down on the vehicle while it’s parked, you’ll see more than a single gyration. A slightly worn shock will be less obvious, but you will eventually notice degraded ride quality.
Aside from the lack of comfort and control, a worn shock will also cause accelerated tire wear, and in some cases, an increase in stopping distance.
Depending on your vehicle, shocks are usually an easy-to-medium level repair in terms of cost and difficulty. The replacement parts tend to be reasonably priced, and there may even be some upgraded components available if you want to improve the driving dynamics. Replacing the shocks will require some dismantling of the suspension system, so expect a few hours of labor to be quoted, though every vehicle is different in this respect.