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By Tire Agent Staff
December 21, 2021
Before we answer the question "What causes dry rot in tires," let's first understand what dry rot means.
Dry rot is a term that's used to describe a fungal condition in wood (thanks to BobVila.com for the wood rot tutorial). Wood dry rot isn't actually caused by dehydration or drying; it's caused by moisture. Because of the way the moisture and fungus eat away at the wood, the decayed effect makes the wood look dry and rotted. Hence, the name "dry rot." In nature, dry rot causes timber to break it down and decompose -- it's a very natural process. In a home or building, dry rot is a nightmare, as fans of house-flipping HGTV shows are well aware.
So, back to dry rot and tires. Dry rot in tires is not caused by moisture or a fungus. Tire dry rot refers to the aging process and breaking down of the rubber and polymer materials. It's also more accurately known as sidewall weathering and sidewall cracking.
Four things cause dry rot in tires:
In the next sections of this post, we explain how each factor affects a tire's life. In reality, it's a combination of age, weather, lack of use, and poor tire care that contribute to tires drying out and rotting.
To get the most miles from your tires, do the following:
Did you know that tires have expiration limited shelf lives? All tires that are sold in the U.S. are required to be stamped with their manufacturing date. In this post, "What do the numbers on tires mean," we explain all the letters and numbers on the sides of tires. Look for the DOT stamp on your tire; the last four numbers are the week and year the tire was made. A tire with 0321 was made in the third week of 2021.
Rubber can be made from organic and synthetic materials, both of which eventually will dry out. We've all found dried up, old rubber bands in the deep recesses of our furniture. They look and feel dry and cracked, and it doesn't take much effort to snap them into pieces, right? The same effect happens on all types of tires -- bicycle tires, vehicle tires, trailer tires, etc.
Vehicle tires have finite life, typically 5 to 6 years. People who live in arid climates, like the deserts of California, Nevada, Arizona and New Mexico, can experience sidewall cracking sooner than people who live in four-season humid climates. Their tires might not last 6 or more years. So, in reality, it's a combination of age and weather that affect how long the tires will last and start to crack and dry.
If you have to store a vehicle (vintage car, UTV, equipment, and even bicycles), Goodyear recommends doing this to prolong the life of your tires so they don't dry and crack:
If you take two identical tires, made on the same day, and place one on a vehicle that's driven every day and one on a vehicle that's stored in a garage, the tire that is driven on every day will last longer than the one in storage (under "normal" driving conditions). Tire rubber is engineered with protective compounds that activate when tires are driven (Polymersolutions). When tires are used regularly, they stay more flexible and more resistant to sidewall cracking. That's one reason why it's important to drive vehicles regularly, even collector cars and seasonal vehicles. Not only does starting the motors help lubricate the parts of the vehicle, but driving on the tires helps prevent tires from drying out.
This is also why tire sun protection or tire preservatives are not effective at protecting tires so they don't dry rot. Today's tire manufacturers build tires with protective materials that preserve and prolong tire life. As long as they are cared for properly, and driven regularly, your tires should not suffer from sidewall weathering.
Tire manufacturers generally say that tire age is between 6 and 10 years, but closer to 6 years. The real "life" of a tire is more about miles driven, which depends on your driving style, terrain you drive on, vehicle you drive and your driving style. However, the shelf life of a tire is about 6 years. No matter how old a tire is or how many miles it's been driven, if you notice cracks in the sidewalls, you should replace the tire immediately.
If you notice cracks in the sidewalls of your tires, it's time to replace them.
We do not recommend that you repair or patch tires that have dry rot. Tires that have started to crack and dry are beyond their useful age and should be replaced. We're not saying this just because we're in the business of selling tires. We'd say this no matter what business we were in: If the sidewalls of your tires show signs of drying and cracking, they are aging and dangerous. Don't drive on weathered tires. They are in danger of blowout.
You will find products for sale that claim to fix dry rot on tires. The only time that you want to "fix" a dry rotted tire is when you are trying to get it to the auto shop to replace the tire.
We recommend that you have your local tire professional look at your tires, if you suspect they have dry rot. The general rule for dry rot on tires and tire safety is the only place you should drive on tires with dry rot is to your auto repair shop.
If you're trying to get as many miles on your tires as possible because price is a concern, Tire Agent offers payment plans that can alleviate the stress of buying a full set of tires at one time.
Are dry rotted tires safe?
Does tire shine prevent dry rot?
No, not really. The best way to prevent tire dry rot is to drive on tires regularly, keep them properly inflated, have them rotated and inspected every few months (with your oil changes).
Can you buy UV protection for tires?
Yes, but the real question is, do these products work? According to Consumer Reports, several tire manufacturers do not recommend using tire dressing, especially for prolonging a tire's life. Today's tires are built to resist ozone and UV damage. Rubber conditioner for tires will make them look pretty, but it doesn't prolong your tire's life.
How do you stop dry rot on tires?
Once tires have dried and started cracking, it's time to replace them. You can prevent tires from becoming dry by caring for them: Drive on them regularly, keep them properly inflated, and rotate your tires as the manufacturer recommends.
How long before tires get dry rot?
Six to 10 years, depending on where you live and how well you care for your tires.
Sometimes, sidewall cracks on tires can be difficult to spot, while other times they are quite obvious. Dry rot in tires can look like tiny, thin lines, like you'd see in crackle-finished pottery. You can spot them on the sidewalls, as well as in the grooves between the tires' treads.
If you spot cracks in your treads or sidewalls, it's time to shop for tires.
Dry rot can appear as very fine vein-like lines in a tire. Even tires that have never been driven can dry out and rot, especially if they're left in the sun or outdoor weather too long.
Look closely at the above photo and in the 10 o'clock position, note what appears to be a crack in the tire. This is likely tread separation and not dry rot. Tread separation is just as dangerous to drive on and needs immediate attention.
In its extremes, above is a tire that has severe dry rot.
Commercial vehicles that spend a lot of time outdoors are susceptible to dry rot (sidewall cracking or sidewall weathering), as you can see in the photo above.
Above is a closeup of a tire with severe dry rot. If you see even one line like the ones above, it's time to replace your tires.