How often should tires be replaced?

Tires are what's holding your car to the road. Worn out tires increase the risk of an accident. We all know that, but at what point should tires be replaced? How do you know if your tires are worn out? Should you opt for different tires or stick with the same brand that came with your car? What can you do to make your tires last longer? We will try to answer these questions in this post.

New vs worn-out tire As you drive, the tire tread material wears out, see the photo. Worn out tires have less grip on the road. An all-wheel drive system, antilock brakes and vehicle stability control system are less effective if the tires don't have enough grip.

How do you know when your tires are worn out? Most auto repair shops check your tires during your regular oil changes. Mechanics inspect your tires for any damage and measure tire tread depth using a tire tread depth gauge. The tire tread depth is measured in 32nds of an inch. New tires have 9/32" to 11/32" of the tread material. A tire is considered unsafe when the tread is worn down to 2/32" (1.5 mm), see the photo above.
New and worn out tire Should you wait until your tires become unsafe or replace them earlier? In our experience, you will start noticing occasional slipping on wet or slick roads when your tires are worn down to about 4/32". At this point, you should start looking for new tires. This will give you some time to shop around and compare ratings and reviews for different tires.

How to measure the tread depth:
How to measure tire tread First, let's do it with the proper gauge. We purchased this tire tread depth gauge for $5 at a local department store. Hold the gauge over one of the major grooves and slightly push the scale down. See the photo. The new tire shows 9/32", while the tire on the right photo shows 4/32".

If no gauge is available, the Washington quarter can help. With a quarter placed upside down, if George Washington's head is covered by the tread, you have more than 4/32" of tread material left.
How to measure tire tread with a quarter Many tires also have tread wear indicators. Tread wear indicators are the rubber bars built into the tread across the main grooves As the tire wears out, tread wear indicators become clearly visible. See the photo below, this tire is worn down to 4/32 of an inch.

Tire wear indicators Worn out tread material is not the only reason for tire replacement. A tire needs to be replaced if it has cracks, cuts, bulges, punctures in the sidewall or any other damage or defect that makes it unsafe. If the tire becomes damaged after driven flat, it will also need to be replaced. See a few examples:
1. Cut in the sidewall
2. Sidewall bulge
3. Puncture in the sidewall (sidewall puncture cannot be repaired)
4. Tire that has sidewall damage after driven flat
5. This tire also was driven flat – it has rubber shavings inside.
6. Cracks in the tire material
7. Unevenly-worn or "cupped" tire
8. Tire worn on one side

Do tires need to be replaced because of the age? Yes, even if the tread is in good condition, the tire material degrades over time. The NHTSA recommends replacing tires that are more than 6-10 years old, regardless of the wear. How can you tell how old is the tire? Check the DOT Tire Identification Number. On the tires produced after the year 2000, the last four digits of the Tire Identification Number indicate the week and the year the tire was manufactured.New vs worn-out tire For example, the tire in this photo was produced on the 34-th week (August) of the year 2008.

Do you have to replace tires with the same brand that was originally installed on your vehicle? No, you can opt for any tires that fall within car manufacturer recommendations (size, speed rating, etc.). In fact, by switching to different tires you can adjust your car's handling to your preferences. If you enjoy spirited driving, you may want to switch to tires with better handling characteristics. If you like a quieter ride, you can select tires that provide better ride comfort.

For example, recently, one of our colleagues was looking to replace the original tires on his Mazda 3. His original tires were worn out and noisy. He switched to Michelin Defender tires and reported a much quieter ride.
Sites like and offer comparisons of different tires on tread life, fuel economy, ride comfort, noise level, handling in snow and other ratings. If you are looking for better fuel economy, look for low rolling resistance tires. If you need more grip on wet roads, look for wet traction or wet braking scores. Replacing all four tires is not cheap, but it's an investment in your safety and better driving experience.

What can you do to make your tires last longer? It's actually easy: opt for tires with longer tread life ratings. Check tire pressure regularly and keep it up to the car manufacturer specifications. Have the tire rotation done as often as recommended in the maintenance schedule. In some cars, if not rotated regularly, tires may need replacement in as early as 15,000 miles.
After tires have been replaced, it's a good idea to have the wheel alignment done.