It’s difficult to know just when it’s time to replace shocks and struts. For one, they go bad slowly, so the reduced ride comfort and road control you’re getting don’t seem out of the ordinary.

Also, there’s no set time or mileage for when aging shocks or struts are due for replacement. You won’t find a set service interval in your owner’s manual.

Third, these parts can be hard to get at, and seeing precisely how worn they are requires expensive disassembly. That’s just not practical or cost-effective.

Bad shocksshock absorber manufacturers and struts are diagnosed through other methods. Here’s what to look for as telltales:

Cupping on tires, especially if a rotation was performed on schedule but abnormal wear is still occurring.
Suspension bushings problems — cracking, peeling, off-center.
Active leaking of oil on parts.
A rougher ride.
Bottoming out (your vehicle’s body or suspension hitting the ground) when going up a parking garage ramp or backing out of a driveway.
Longer stopping distance.
Swaying after a turn or lane change or in cross winds.
Noticeable bounciness (more than one or two bounces) after going over dips or bumps.
Nose-diving when you apply the brakes.