Unused Tires Still Age: The Garage and Spare Myth

The myth

"It's never been on the road, so it's basically new." People say it about the set of tires in the garage, the spare that's never been used, and the bargain "new old stock" tires that sat in a warehouse.

Tread depth is the only thing that stays new. The rubber keeps aging from the day the tire is made. Here's what NHTSA and tire makers say, and what it means for the tires sitting in a hot Florida garage.

What the evidence says

Tires age whether or not they roll. NHTSA's TireWise guidance says tire aging comes from service, storage and environmental conditions. Storage is on that list. A tire on a shelf isn't wearing its tread, but it is getting older.

Age limits are measured from manufacture. NHTSA notes that some vehicle and tire makers recommend replacing tires that are 6 to 10 years old, regardless of treadwear. Bridgestone and Michelin recommend a professional inspection at least once a year from five years old, and replacement 10 years after the tire was made, even if the tread looks new. Your vehicle maker may set a shorter limit in the owner's manual. Our guide on how old is too old compares the recommendations.

Heat speeds it up. NHTSA's research found tire aging is a greater concern in the southern Sun Belt. A closed garage in a Broward summer is a warm place to keep rubber.

So the myth is backwards. A stored tire doesn't stay new; it just stays unworn.

Where unused tires hide

The spare. It's often the oldest tire on the car, because it rarely touches the road and may be as old as the car itself. Bridgestone's guidance is to check the spare and replace it if it's more than 10 years old, even if it appears new. Our spare tire types guide explains what kind you may have.

The set in the garage. Old wheels and tires kept "just in case," or a second set for a car you sold. Their age started at their date code, not when they came off the car.

New old stock. A tire can sit in a warehouse before it's sold. NHTSA's Tire Buyers' FAQ suggests checking the date code when you buy and knowing your vehicle maker's recommended replacement timeframe. Our post on how old tires are when you buy online covers what to ask.

The car that sat. Snowbirds know this one. Our post for cars that sat all summer covers the tires still on the car.

Find the real age

Every tire carries a DOT code on its sidewall. The last four digits are the week and year it was made. Try reading one:

Our DOT date code guide shows where to find it, including on tires that only print the full code on one side.

How to store tires in a Florida garage

You can't stop aging, but storage makes a difference. Michelin's advice for stored tires:

• Indoors, in a clean, cool, dry and dark place, out of direct sunlight.
• Away from heat sources such as hot pipes, and away from ozone sources such as electric motors and generators. That includes the garage freezer, the pool pump area and the generator you keep for hurricane season.
• Clean and dry before storage, so nothing corrodes on the wheels.
• Mounted on wheels? Stack them horizontally. Unmounted tires can stand upright, side by side.

In South Florida, the coolest dark place you have is often inside the house, not the garage. A covered spot off the concrete, away from the water heater and the generator, beats a sunny corner.

Should you buy tires ahead and store them?

Sometimes it makes sense: a second set of wheels, or a spare set for a vehicle you'll keep for years. But buying far ahead just to have tires on the shelf uses up part of their life before they ever roll. Three questions to ask first:

1. How long until they'll go on? The longer the wait, the more of their age limit they'll have used.
2. Do you have the right place to store them? Cool, dry, dark and away from ozone, per Michelin. Many South Florida garages don't qualify in summer.
3. Will the size still be right? If you change cars, a stored set may not fit the next one.

Don't forget the spare's pressure

An unused spare loses air like any tire. NHTSA says to check pressure monthly on every tire, and that includes the spare. A spare that's in date but flat won't help on the shoulder of I-95.

Before you mount stored tires

1. Read the DOT date on every tire, not just one.
2. Look closely at the sidewalls and tread for cracks, bulges or flat spots.
3. Have them inspected if they're five years old or more, as Bridgestone and Michelin recommend.
4. Check that they match the size, load index and speed rating on your door placard.

The verdict

If the spare or the stored set is past its limit, shop by size and ask about the DOT date on what you buy. Shipping is free to the 48 contiguous states and DC, and in Miami-Dade, Broward and Palm Beach we install at our Sunrise shop or by mobile van. Not sure about the set on the car? Do I Need Tires Yet? walks you through it.