Whether you drive a truck for yourself or for a company, the ultimate responsibility for safety is on you — so it’s important to know how to spot tires that need to be replaced.

Since tires are expensive, you don’t want to replace them unless it’s really necessary, but these are the signs of tires that are past their prime:

The wear indicators are flush with the tread

New tires have cross “ribs” that are gradually exposed and become level with the rest of the tire tread as the tread wears down. When they start to be flush in spots with the tread, it’s time to plan updates for the tires. (If you have older tires on your truck that lack wear indicators, you need to keep a close eye on the tread yourself. Once it’s less than 1.6 millimeters deep in any spot, it’s time to replace the tires.)

You see bulges or blisters on the sides

A blister-like bulge on the side of a tire is automatically a cause for concern. You need to get an immediate replacement — otherwise, you’re risking a blowout and a major accident every time you’re on the road.

You spot cracks or grooves on the sidewalls

Bulges aren’t your only concern. Cracks, cuts and grooves that are visible on the sidewall of a tire are also immediate concerns. They indicate that a tire is leaking air and is ripe for a blowout. Get the tire replaced before you agree to drive anywhere.

You feel the vibration of the road a little too well

If you’re brand new to trucking, you may not notice this, but any experienced trucker knows what the road should feel like under his or her wheels. If the road seems particularly rocky and rough, it could be a problem with your tires. They may simply be unbalanced — or you may need to replace them.

Tire care is too important of a safety issue to overlook it. One of the best ways you can avoid a preventable truck accident is to get into the habit of checking all of your tires before you head out on a trip.