Used Tires - A Complete Guide

‍Are Used Tires Safe?

Yes, used tires can be a safe and affordable way to put tires on your car. Many used tires are essentially brand new, and others are offloaded by tire shops if they were replaced before their time.

Used tires can be 25% to 75% cheaper than new tires, and if they're relatively new and have good tread depth, they can last almost as long. But you need to be careful when purchasing used tires, especially if the tread is worn down.

Used Tires and Tread Depth

Tread depth is the height of the tread on a tire, which is the thick serrated rubber that contacts the road. Tread depth differs widely-obviously, large BFG mud tires will have a significantly deeper depth than no-name street tires, but standard measurements can still be used to determine its useful life.

Tire tread should remain within the safe tread range for between 30,000 and 50,000 miles. Using a tread depth gauge can help you determine how many miles a tire has on it.

For road tires, the factory tread depth is usually between 6mm and 8mm. A used tire still has some life left in it when the tread is between 4mm and 5mm, but any tire with 3mm or less of tread depth is on its last legs.

Used Road Tires vs. Used Off-Road Tires

Off-road tires have significantly more tread height than standard street tires. Additionally, since they usually have more gaps between the tread, the tires wear down on the highway much faster than road tires.

An off-road tire with 3mm of tread depth left is usually a lot more worn out than a road tire with the same tread depth. Additionally, it likely has fewer miles on it due to the increased speed of tread loss.

How to Measure Tire Tread Depth

Measuring tire tread depth is easy, and all you need is a $3 auto parts store tread gauge. First, look at how the tread on the tire separates. There are usually four channels that run around the length of the tire, and you want to measure from the central two channels.

Simply place the gauge in the tread channel or between the tread and measure how deep it goes. Usually, 'good' is marked with green, 'decent' is marked with orange, and 'replace' is marked with red.

How to Tell the Age of a Used Tire

Tires come with a lot of information written on the sidewalls. In many cases, tires also have a date code that indicates the week and year of manufacture.

If you've ever had an old or classic car, this situation may be familiar: you blow a tire and look for the spare, only to discover that it is deflated and fossilized—because the date code says it was made in 1981.

Tires don't last that long, so it's essential to read the date code on used tires regardless of how good the tire looks. Tires made 30 years ago look exactly the same as brand new tires, so there's really no other way to know.

So, how do you find the date code on a tire? If it has one, it'll usually be located after the DOT registration and tire size designation. The date code has four numbers, such as "3301." The first two, in this case, 33, indicate the week that the tire was made. That's sometime in August. The second two numbers, 01, indicate the year. In this case, 2001.

If you were to encounter a tire with a 3301 date code on a used tire lot, you should probably avoid it as the tire is 20 years old, and nobody knows what kind of condition the rubber is in.

The Lifespan of Used Tires

How old can a used tire be, and how safe is it? In the example above, we used a tire with a 3301 date code which was produced in August of 2001. A tire like this is a pretty solid example of a no-go, regardless of what condition it appears to be in.

Tires have a limited useful life. At most, a tire should last about 5 to 6 years on the road or outside on a used tire lot. Anything beyond that is taking chances with decomposition, as both natural and synthetic rubber decay and lose elasticity with time.

As a general rule, only purchase used tires that are between 2 and 5 years old. These tires should still have useful tread depth, and they haven't been around long enough to experience most forms of serious tire decay.

Once they're installed on your car, you can use them for a few years without too much concern. This is because you're the owner and can keep an eye on the condition. Plus, you'll notice cracks and decay immediately if they're inflated on a car.

Used Tire Storage

Tires are made of natural or synthetic rubber—mostly natural rubber. Natural rubber is latex, which is harvested from rubber trees primarily in Southeast Asia. Rubber, being an organic material, decomposes when exposed to the weather for too long.

Tires left out in the sun—especially in the desert—can reach varying levels of decay depending on their initial condition, age, and how long they've been sitting outside. This is an important factor to consider when purchasing used tires.

That said, just because a tire is stored outside doesn't mean that it's junk. As with all used tires, when purchasing tires stored outdoors, use caution and inspect the sidewalls and tread for cracks. Press down on the tire and make sure it has a rubbery consistency and isn't hard as a rock. If the surface cracks when it is stressed, walk away.

Used Radial Tires

Radial tires are by far the most common kind of tires used on modern cars. Radial tires have a band of steel sandwiched between layers of rubber. This steel band helps protect the tire from puncture through the tread—but doesn't protect the sidewall.

Radial tires are also the most common kind found on used tire lots. These tires last a long time, and provided the tread is in good shape; they should be perfectly safe to use again. These tires are safe to use on virtually all kinds of vehicles, both new and classic.

Used Bias Ply Tires

Bias-ply is an older kind of tire, and it can occasionally be found on used tire lots. Bias-ply tires have largely been replaced by radial tires, so finding them on used tire lots in usable condition is rare. Bias-ply tires use corded rubber for strength instead of steel.

You should probably stay away from any kind of bias-ply tire unless you're specifically looking for one. These tires are often much older than they look, and the outside condition is no fool-proof indication of their road safety.

One exception is for classic vehicles, as new bias-ply tires are still manufactured with white walls and other bias-ply tread patterns. These replica tires can sometimes be found in good condition on used tire lots—just be sure to check the date code and inspect the rubber for cracks.

Can You Mix and Match Used Tires?

Yes, you can mix and match used tires as long as the size and tread type is the same. Generally, though, it's always better to get a matching set, so they're not unevenly worn.

Also, don’t mix bias-ply tires with radial tires if you can avoid it, because the wear patterns and tread type of these types are quite different.

It's better to get four tires from the same vehicle that are made by different companies than to get four of the same brand from different vehicles. But the brand doesn't matter much if the tires fit and aren't badly worn.

Can I Run Worn Out Tires Safely?

This is an interesting question with a fairly simple answer. If a tire has cracks in the sidewall, numerous patches, or smooth worn-out tread, it can't be used safely. But in a pinch, many people buy these worn-out tires assuming they won't randomly explode.

And quite often, they don't randomly explode on the highway. But they may deflate overnight, and they're much more likely to get punctured or rupture—especially at high speeds.

Additionally, tires with no tread are extremely unsafe in wet conditions and cause a large portion of accidents. Around 15,000 accidents in the United States are directly attributable to tires, so it's essential to be smart and find a set that's not too old and has good tread.

How to Maintain Used Tires

Maintaining used tires is relatively straightforward. You should periodically clean them and inspect the tread for nails, which should be repaired promptly.

It's a good idea to replace the Schrader valves and valve caps when you get new tires. These are the one-way valves that you use to fill the tire, and they're a lot easier to replace when the tire is off than when the tire and wheel are bolted up to the vehicle.

Additionally, wash and apply tire protectants like Armor All regularly. Get your wheels balanced immediately after installing new tires, and have your tires rotated periodically to ensure a long tire life. Also, check the tread depth once every 5,000 to 10,000 miles, and check tire pressure regularly.