Your tires can affect every aspect of your driving, from stability and control to gas mileage and braking. Worn tires can lower the performance, efficiency and safety of your vehicle and should be replaced when they begin to show signs of excessive wear. That said, not all worn tires need to be replaced. Aging tires can often still be usable with a tire rotation or vehicle alignment. A properly maintained set of tires usually will last for at least 50,000 miles. If you feel your aging tires are becoming a safety hazard, ask yourself the following questions to get a better understanding of what to do next.

Are my tires wearing evenly?

You can drive on your tires longer if the tread is wearing evenly on all four of your tires. You can help even out your treadmill by rotating your tires each time you get an oil change; most places will do it for free. Equally important is making sure the edges of your tires are wearing evenly. If they're not, that could mean you have an alignment issue, and you'll need to get that fixed when you buy new tires.

Are my tires safe in the rain?

At a certain point, tires really start losing their grip on wet roads. You can check this yourself by sticking a penny between your tire treads, and if Lincoln's head sticks out from the treads, then you probably need new tires. Or, you can ask a salesman for a professional opinion.

Can I get away with just replacing two tires?

If you're low on cash, often you can just buy new tires for the front of your vehicle, assuming your car or truck is front-wheel drive. You may even be able to buy new tires for the back and rotate the rear tires to the front, and then switch the rear and front tires later on.

Do my tires pass the penny test?

Try the penny test to see if you're ready for new tires. All you do is take a penny and put it between your tire treads. If you can't see Lincoln's head, then your tires are fine. If you can see his head, then you should consider new tires.

Has my tire already been repaired?

Some people drive on older tires figuring they'll just repair them if they go flat, but some tire shops won't repair tires that have already been fixed once. At a certain point, tires simply become too unstable to and unsafe to drive on, and a patch wouldn't do enough good.

Is my spare tire properly inflated?

If you're worried about the tires on your car, then you should be just as concerned with the spare tire in your trunk. Everyone gets flat tires eventually, and when that happens, you'll want to make sure you're able to get to a repair shop without needing a tow truck. Making sure your spare is properly inflated is even more important for people who are driving on older tires.