Dry rot, sometimes called sidewall cracking, refers to the small cracks that form on the side of a tire. They start out as small, hairline cracks that are often difficult to see, and eventually extend all the way to the tread and can become quite large. The rubber itself can also turn from black to an ash-gray color. Dry rot poses imminent danger in tires, as the cracks eventually lead to air escaping – this can cause flat tires and dangerous sidewall blowouts. The environment is mostly responsible for causing the rubber (a natural compound) to break down, but it’s not the sole perpetrator.
1. Oxygen – This is perhaps the most damaging to tires because it affects both the outside and inside of the tire. Obviously tires encounter oxygen externally, but the compressed air inside a tire is also approximately 21% oxygen, so this degradation happens internally as well.
2. UV light – This radiation comes from the sun. Multiple polymers (natural and manmade) that make up the rubber will absorb sunlight and subsequently break down as soon as they are exposed to this form of radiation.
3. Ozone – This is another form of oxygen, but there is a lot of manmade ozone in our atmosphere from various sources of pollution. It is particularly damaging to tire rubber, so areas like big cities (with more pollution) will actually see tires dry rot more quickly than rural areas (with less pollution).
4. Temperature fluctuations – When tires are exposed to extreme and rapid changes in temperature – particularly high heat – they will break down more quickly.
5. Infrequent use – When tires sit for long periods of time without being used, they deteriorate at a faster rate. This is because tires include a kind of wax that is used to protect them from oxidation; it only reaches the surface of the tire when it’s driven. When tires aren’t used, the surface rubber doesn’t get the benefits of this protective wax.
6. Tire shine – Products that are applied to the outside of the tire to make them look shiny will dry them out and expedite the dry rotting process.
7. Age – Regardless of how well you shield a tire from the elements, they will dry rot at some point. The industry standard is to replace tires once they are 10 years old, regardless of how they look. However, tires that are 5-6 years old are at risk for dry rot, so most tire shops won’t sell tires older than that, even if they’ve never been used.
What Can Be Done?
While some of the above contributors may be avoided, dry rot is inevitable and will eventually happen no matter what you do to escape it. There is no way to repair dry rot. Some claim that, if caught early enough, certain products can be used to seal small cracks and prolong the tire’s life; however, these methods are not universally agreed upon. The industry standard – and the safest way to address the issue – is to replace your tires once you notice dry rot. Because dry rot can often be difficult to see in its early phases, and can also happen inside the tire, it’s best to have your tires inspected regularly by a professional.
How to Prolong Tire Life
There are certain things you can do to prolong your tire’s life and put off dry rot as long as possible. Avoiding the elements – sunlight, water, and harsh temperatures – will be your best bet at combating the issue.
If you’re able to store your vehicle and/or spare tires indoors (like in a garage), do it.
Do not let your tires sit unused for long periods of time. Even relatively short drives (a few miles) at frequent intervals can keep your tires in better condition than if they sit in one position for a long time.
Do not use tire shine on your tires, and if tire shine is on them when you purchase your vehicle, wash it off. If your local car wash uses it, you can ask them not to apply it to your tires.
However, you should avoid over-washing your tires, as excess exposure to water and soap can actually dry them out.
You should consider using nitrogen-fill in your tires rather than normal compressed air. Nitrogen-fill has a much lower percentage of oxygen than regular air, so it may help slow the process of dry rot on the inside the tire.