Car tires are the only parts of a vehicle that directly contact the road while driving, whether cruising comfortably or rushing to make it to the restroom in time. Although tires aren't the most expensive component on a car, they can determine whether everything else remains fine or ends up broken down roadside. Checking tire condition is therefore very important. This Thairath Online Sunday article discusses how to check tires and when to replace them.
After recently writing shorter columns because readers preferred them—and I, Arkom Ruamsuwan, also liked it since it's quicker to check—well, this suits me perfectly. Writing long pieces can tire readers searching for information while blocking pop-up ads. But sometimes, following the trend of readers not wanting long texts is acceptable. This week, I write about tires because I recently wished a happy birthday to Na Plin, one of the senior figures in our automotive media, telling him not to get nails in his tires often this year. Na Plin is lucky in many ways, except when it comes to nails or sharp objects puncturing his tires; he seems to encounter that bad luck more than anyone else. So, I decided to write about tires.
To determine when it's time to replace your tires, several factors come into play. The simplest, albeit cheeky, rule is: if after changing tires you find the car doesn’t grip the road well enough, isn’t smooth, or performance is unsatisfactory, it's time to replace them—if you can afford it. Or secondly, if your wife complains that the tires feel too harsh, of course, you should replace them as soon as possible. But if we disregard these two points, then we must consider the tire condition from several aspects.
First is the tire’s service life. Essentially, we count from the date the tire started bearing weight or was first used on the road. Tires stored properly can last up to five years without performance degradation. I say this because I once tested tires aged 1, 3, and 5 years on a track, and lap times differed by less than one second. To be safe, stock tires shouldn’t be older than 3 years. After installation, wear occurs with use. Generally, from my experience, whether low-cost or high-cost tires (excluding racing tires), they typically last about 50,000 kilometers without causing you to have an accident roadside.
Therefore, my simple and safe guideline is that tires in use should be replaced after 50,000 kilometers. For vehicles driven less, even if only 10,000 kilometers per year, tires should be replaced after 5 years. If unsure whether to replace or not, or if you bought a used car and the previous owner doesn’t remember when the tires were changed, check the four-digit number on the tire sidewall inside a capsule-shaped box, such as 1124 or 5023. The first means the tire was made in week 11 of 2024; the second, week 50 of 2023. For example, if it’s 2025 and you see 2119, the tire was made in 2019. If you have money left, replace it because even if the tread remains, you can’t be sure the rubber still grips well.
Remember, a stock tire stored for five years is different from a tire that has been mounted and used for five years. Also, sometimes you don’t know how many kilometers the previous owner drove on it.
If we ignore obvious old tire age, what else can we check? Next is tread condition. Tread is especially important in rainy areas. On dry roads, rubber grip is key, but on wet roads or puddles, tread channels water away quickly to prevent hydroplaning. Tread usually has wear indicators called tread wear bars—small raised lines in the grooves. If the tread wears down to the level of these bars, it’s time to replace the tires. If you can’t find the bars, estimate visually: if tread depth is less than 2 mm, replace the tire as it won’t drain water effectively.
Additionally, on the outer sidewall is a small triangle mark about the size of a cicada called the sidewall triangle mark. While tread wear bars indicate tread wear on the tire’s surface, this triangle indicates sidewall wear. If this mark fades or disappears, it’s time to replace the tire. If the triangle is nearly gone but tread bars remain, it may mean you take corners hard. If your wife knows how to check tires, she might scold you. Sometimes, misalignment causing wheels to tilt inward or outward (visible from front or rear) can cause sidewall wear faster than the tread center. Besides changing tires, checking wheel alignment is recommended.
External tire appearance can also help assess condition. Cracks or checks on sidewalls indicate rubber deterioration, perhaps from frequent driving in hot conditions or loss of rubber elasticity, suggesting replacement is needed. Bulges on the sidewall from impact may mean structural damage. If you can’t afford new tires immediately, avoid harsh driving. Similarly, punctured tires can be patched and reused, but patched tires require frequent air pressure checks. If patched tires don’t leak compared to others, they’re usable but should not be driven at high speeds aggressively.
Cuts or tears in the tire rubber vary. If they cause air leaks, the tire must be replaced. For shallow cuts, such as from sharp stones, check depth. For soft passenger car or eco-car tires, cuts less than 1 mm deep can be used further. For trucks or off-road tires with thicker sidewalls, cuts 2-3 mm deep may still be usable. However, you should manage your own risk based on experience.
Another factor to consider is abnormal tire behavior during driving. If one tire loses air faster than others after 500-1,000 kilometers, it might indicate tire deterioration or valve stem failure, which a tire shop can check. Also, deteriorating performance such as brakes causing tire squeal where none existed before, loud tire noises when cornering, understeer or oversteer, howling sounds, or unusual noises not present when tires were new, all suggest tire issues.
If the noise sounds like a four-stroke motorcycle chasing you, that’s a wheel bearing issue, not a tire problem. But if you recently replaced wheel bearings and hear that noise, check if you accidentally left the gas station without paying and the attendant and manager are chasing you. Tire noise from worn tread often sounds like a diesel locomotive passing about 20 meters away, especially when driving at 90-110 km/h. Vibration while driving doesn’t always mean tire wear; sudden vibration that wasn’t present before may be due to lost wheel weights inside the rim, possibly from adhesive failure or high-pressure washing. Without the weight, the wheel runs unbalanced and vibrates.
Some try to check tire hardness by pressing with a fingernail, but this works only if you have prior experience comparing new tires. For most people, this is difficult. It’s better to use other methods. Importantly, tire condition checks should be done regularly, at least once a month or every 10,000 kilometers, for safe driving. If the car is parked at home, inspect the tread surface. Even better, if you don’t like doing vehicle maintenance yourself and have time and money, visit a tire shop to rotate tires front to rear or cross-rotate, depending on tread pattern compatibility. When tires are removed, observe sidewall condition inside and outside. Some tire blowouts occur due to unseen inner sidewall wear or cuts, which you can only see by crouching down and looking closely. Be careful.
That’s enough about tires this week. If you realize you haven’t checked your tires in a long time, close this page and go check your tires now. Checking air pressure is one thing, but inspecting tire condition is a different matter. Wishing you safe and happy travels.
Pan Paitoonpong