Sun, Heat and Dry Rot: How Florida Ages Your Tires

The cracks you notice while pumping gas

You're at the pump, glance down, and see it: a web of thin lines across the sidewall, or little cracks at the base of the tread blocks. The tread still looks deep. So is the tire wearing out or not?

In South Florida this question comes up a lot, because the conditions that age rubber are the ones we live in all year. Here's what the cracking is, why the climate speeds it up, and how to tell the harmless-looking kind from the kind that means new tires.

What "dry rot" actually is

Goodyear defines tire dry rot, also called sidewall weathering, as visible cracking in a tire's tread or sidewall caused when the rubber compounds break down. The signs it lists:

• Cracking in the sidewall, often as a web of hairline cracks or lines running around the tire
• Cracking in the tread, usually at the base of the grooves
• A brittle surface that feels hard rather than supple
• A faded or gray color in place of the original black

Michelin calls the early, hairline version weather checking: a sign the rubber has started to dry out.

Why Florida speeds it up

Tire rubber contains weathering agents meant to protect it, but they don't last forever. Several things wear the rubber down faster:

• UV from sunlight. Goodyear says too much UV exposure, especially in consistently warmer climates, is a leading cause of premature sidewall weathering.
• Heat. NHTSA lists exposure to sunlight and a warmer climate among the factors that contribute to tire aging, and says aging is a greater concern in the more southern parts of the Sun Belt states. That's us.
• Ozone. Michelin warns that ozone from electrical equipment and UV from sunlight are among the most damaging things a stored tire can face. It says a tire stored next to an electric motor or against a sunny wall can crack within weeks.
• Sitting still. NHTSA lists infrequent use as an aging factor too. A car that sits in a sunny lot for weeks, or all summer, gets the exposure without the flexing.
• Low pressure. Goodyear lists underinflation among the causes, because it overworks the sidewall.

None of this gives a Florida tire a set lifespan. Nobody publishes a "Florida number," and we won't invent one. It does mean that here, the calendar and the sidewall deserve as much attention as the tread.

Which cracks matter

This is the part drivers most want to know, and the honest answer is that it takes a trained eye. NHTSA says plainly that you cannot detect tire aging simply by looking at your tires. Still, the makers give a useful split:

Goodyear's view is that once deterioration becomes noticeable, the best course is to replace the tires. If you're unsure, that's exactly what an inspection is for. A bulge is a separate, more urgent problem; our guide to sidewall bubbles explains why.

Check the age while you're down there

Cracking and age go together, so read the DOT date code on the sidewall: the last four digits are the week and year it was made. Try it here:

Then compare it with the guidance:

• Michelin: after five years in service, a thorough inspection by a trained professional at least once a year, and replacement ten years after manufacture regardless of tread.
• Bridgestone: an inspection is essential after five years, and tires made ten or more years ago should be replaced. Same for the spare.
• FLHSMV: Florida's tire safety page is stricter, saying never to operate a vehicle on tires more than six years old.

Our guide to how old is too old lays the guidance side by side, and our DOT date code guide shows where to find the code.

How to slow it down

You can't stop rubber from aging, but you can avoid speeding it up:

1. Park in the shade when you can. A garage, a covered space or the shady side of the lot all cut UV exposure.
2. Keep the pressure at the door placard, checked cold, once a month. Our pressure guide shows how.
3. Drive the car. If it will sit for weeks, see our post on a car that sat all summer.
4. Clean with soap and water. Goodyear recommends water and a mild dish soap and warns that petroleum-based cleaning products may degrade the rubber's weathering agents and lead to early cracking.
5. Store spare tires indoors, cool, dry and dark, away from motors, generators and sunny walls, as Michelin advises. Our post on unused tires aging covers storage.
6. Look monthly. Goodyear suggests inspecting sidewalls and tread every month for cracks, discoloration and bulges.

For more on what Florida heat does to pressure and load, see our guide to Florida heat and tires.

If it's time

Not sure your tires are done? Do I Need Tires Yet? walks you through tread, age and damage. If they are, shop by size or vehicle and check the new tires' DOT dates when they're mounted. In Miami-Dade, Broward and Palm Beach we install at our Sunrise shop or at your home or office with our mobile van. Shipping is free to the 48 contiguous states and DC.