When the casing on your bike tire starts to dry rot, there’s no question if it’s deteriorated. The only questions are why did it happen, how bad is it, and what (if anything) can you do about it?
A tire has dry rot when cracks appear in the treads or sidewall. This usually occurs due to age, wear and tear, improper storage, or all three—and it’s a sign that the tire is on its last legs.
If you see dry rot on your bike’s tire, the right thing to do is to discard it and replace it with a new one. This is especially important on tubeless tires, as the tire itself is meant to hold air pressure.
Contrary to what some cyclists think, dry rot shouldn’t be neglected on clincher and tubular tires, too. When dry rot sets in, the rubber is no longer in its prime and doesn’t have the smooth roll and puncture protection it once did.
In other words, riding with rotted tires is a recipe for a flat or a blowout. And, although there’s no good moment for your bike’s tires to fail you, by Murphy’s law it always happens in the worst possible moment!
Let’s break down the causes of dry rot and what you can do to prevent it in more detail.
Why Do Tire Casings Dry Rot?
Tire casings are made mostly out of rubber, and rubber doesn’t last forever.
Over time, even the highest-quality bike tires oxidize and dry out, losing their protective oils and drying out. When it happens, the rubber is no longer supple and becomes brittle. Cracks form and the tire starts to break apart.
If you don’t use your bike very often—or you live in a state with extreme temperatures and rough weather—there’s a risk that your bike’s tires will rot faster. Dry weather, sunlight exposure, and high temperatures are the top causes of dry rot.
Unlike dry rot on wood, which is caused by fungi and can spread from one plank to another, dry rot on tires is caused by age and deterioration, and will not spread from one tire to another. (Although it isn’t uncommon for both of your bike’s tires to develop dry rot if they are the same age.)
To better understand dry rot, we should take a closer look at all the factors that lead to it.
Weather That’s Too Hot or Too Cold
Temperature is an important factor in the development of dry rot, so you need to think about where—and how—you store your bike. Is it well protected from heat and frost?
Air gets denser in the cold and expands in the heat. This means that you can squeeze more air into your tires in frosty wintertime than you can in sultry summer. It also means that extreme temperatures will affect tire pressure, causing the rubber to contract or expand.
If this happens repeatedly, the rubber will break down faster. Sooner rather than later, its degradation becomes visible to the naked eye in the form of dry rot.
Tip: Keep your bike where it’s temperate. If you keep it in your home, do so away from heaters and air conditioners. If you store it in the backyard, especially for long periods of time, consider getting an all-weather bike cover.
Not Keeping Your Tires Well Inflated
When the tires are topped up to the proper pressure, they will hold their shape instead of deforming under the weight of the bicycle during storage and the weight of the rider and bicycle combined during cycling.
The air absorbs and distributes the weight evenly, ensuring that no part of the tire deforms. This, in turn, helps the tire to stand up to dry rot and keeps it in mint condition for longer.
Tip: Top up your bike’s tires with air before every ride. Air permeates rubber and bike tires lose tire pressure over time—even when they’re brand new—so check on them at least once every 1-2 weeks.
Exposure to Corrosive Liquids
You might be thinking that you seldom expose your bike tires to corrosive liquids, but you do almost any time that you ride it. The petrochemicals on the roads, such as oil, gasoline, and propylene-based anti-freeze, will come into contact with the tires.
How severe this factor is depends on where you live and what time of year you use your bike. For example, the salt and liquid de-icers that they spray on Nordic and Western European roads in winter can eat away and degrade the rubber of your tires in a very short time.
Tip: When in doubt, scrub the tires with lukewarm water, dish soap, and a soft sponge, then give them a dry and pat them dry with a rag. This will remove the residue and help the tire to last for longer.
Mud and Moisture
You may think that mud and moisture can’t possibly cause dry rot on your tires—and you’d be right. However, their evaporation off the tire’s carcass can, and very often does, cause it to dry out excessively.
When water evaporates from the surface of your bike’s tires, it evaporates along with many of the protective oils in the rubber that help to keep it moist and supple. This is also the main reason why it’s not a good idea to park or store your bike when the tires are all muddy and wet; they need to be washed and blotted.
Tip: If you ride your bike on muddy terrain, whether for commuting or recreation, give them a good rinse with the garden hose before storage and pat them dry with an old rag (or at least shake the water off).
As any beachgoer can attest to, the sun’s rays are not kind to the skin—and one needs protection. They are also not good for your bike’s tires and can quickly cause dry rot to set in.
Your bike should not be stored in direct sunlight, or you will find that the rubber in the tires starts to break down and develop cracks quite quickly. This is particularly true in Tropical, Pacific, and Mediterranean climates, but will occur anywhere if too much sunlight falls on the tires.
Tip: If your bike is being stored outdoors, cover it, with an old bed sheet or an all-weather bike cover, to keep the sun off the wheels and ensure that the rubber is protected.
Tires are meant to roll. So, to keep them spick and span, you need to use them.
Even if you are a recreational rider and you don’t take your bike out very often, go for a quick ride at least once a month. To be helpful, this needs to be long enough to warm the tires up.
Doing this regularly helps to keep the rubber supple and flexible, and this prevents it from rotting. You don’t have to do this daily, but frequent short rides will keep the tires in better condition than long, infrequent rides.
Tip: Take your bike out once per month. Apply Armor All tire protectant, or any other high-rated tire protectant, to the sidewalls if you see them drying out.
Dry rot on a bike tire is frustrating and cannot be repaired (although you may be able to reverse it in the early stages) so it’s important to know what causes it and how to prevent it.
Taking good care of your tires will reduce the risk of dry rot and make them last longer.