車の所有者は車体の傷や汚れに気を配るが、タイヤの点検や交換については知識が不足している場合がある。タイヤ交換時にはスリップサインや製造年月日を確認する必要があり、タイヤの摩耗や負荷などの要因を考慮して交換時期を決定することが重要。スタッドレスタイヤの場合も点検が必要であり、未使用のタイヤは適切に保管することが重要である。専門家に相談し、タイヤの交換方法や保管方法を学ぶことが安全運転につながる。
Owning a car makes you concerned about scratches and dirt on the body. Many people check them frequently because they can see it themselves. On the other hand, what about tires? Tires are essential for driving a car, but for those who are not familiar with cars, they may not know how to inspect or replace them. If you use the car for your child’s lessons or club activities, imagine if the tires wear out and cause an accident… It’s scary to think about, isn’t it?
So, let’s consult with an expert. Mr. Hiroyuki Ishikawa of Omakase Auto Ishikawa in Nasu-Shiobara City, Tochigi Prefecture, will explain the inspection and replacement methods for tires.
Tire Replacement Checkpoint 1: “Tread Wear Indicator”
–We don’t usually pay much attention to car tires, but they are consumables, so they need to be replaced at some point. What criteria should we use to determine when to replace them?
Mr. Ishikawa, Omakase Auto Ishikawa Representative: To determine the time for tire replacement, there are mainly two methods. One is the “tread wear indicator.”
When you look at the groove extending from the apex of the triangular mark on the side of the tire, it looks like small mountains. This is a sign of skidding. It is dangerous when the tire wears down to the height of this skid mark.
When you measure the depth of the groove with a dedicated tread gauge, it will be about 7mm.
The depth of the skid mark groove is about 5mm, so when the tire wears down to the skid mark, there is only 2mm left. It is dangerous to reduce it further. It is best to replace it before signs of skidding appear, and the groove depth must be at least 1.6mm to pass the vehicle inspection.
–If you don’t drive much, the wear on the tires will be less, right?
Mr. Ishikawa: Indeed, if you don’t drive the car, the tires won’t wear out, but there is a possibility of cracks forming in the tire’s side wall if you don’t drive. This is because the same part of the tire is always facing downward, causing weight to be placed on that part. Driving too fast on the highway can cause a burst tire to explode. In some cases, whether there are cracks in the tire’s side wall is more important than the tread depth.
Tire Replacement Checkpoint 2: “Manufacture Date”
–What is the second checkpoint?
Mr. Ishikawa: You can also determine this by looking at the manufacture date stamped on the tire.
This tire is made by Dunlop and has a label that reads “IB1023”. The first two digits of the 4-digit number represent the week, and the last two digits represent the year. In this case, it was created in the 10th week of 2023. This applies to all tire manufacturers.
–How often should tires be replaced after they are manufactured?
Mr. Ishikawa: This is entirely influenced by how much you drive on a daily basis, making it difficult to judge. However, generally, the recommended lifespan is 5 years from the initial use. As mentioned earlier, it would be good to mark the skid marks on the groove to check and regularly inspect for any cracks on the side.
–Is there a need to inspect studless tires when driving on snow-covered roads?
Mr. Ishikawa: Studless tires are slightly different from regular tires. In addition to checking for grooves and cracks, we also check if the tires are getting harder when pushing on them. Normal studless tires are surprisingly soft when pushed by hand. The grooves absorb the snow sponge-like and quickly remove it. If the tire becomes hard, it won’t be able to do this, and even with the grooves, it will slip. I only use studless tires in winter, and I think the guideline for replacement is every 3 years.
It is better not to stack unused tires. ?
–If you have to change tires seasonally, you need to store the ones you don’t use. Are there any appropriate storage methods?
Mr. Ishikawa: After changing tires, it is best to wash and air dry them, storing them in a place where they don’t receive direct sunlight. If you had them changed at a gas station and they were placed in a plastic bag for you, you can just keep using that plastic bag.
–Considering storage space, I am thinking about stacking the tires. Is that a good idea?
Mr. Ishikawa: Actually, it’s ideal to arrange them vertically. Stacking them is not recommended. When stacked, the pressure on the bottom tire increases, increasing the risk of tire deformation. However, it may be difficult due to space constraints, so using a storage service is also an option. You can store them securely, so you won’t need to take them out of the warehouse when you need to put them in the car for tire replacement.
Editor’s Note
We don’t usually pay much attention to tires, but I learned that they need to be replaced at some point. In order to drive the car safely, it seems that checking the tires is as important as the car itself. The next article explains how to reduce tire wear and how to choose when buying.
To be continued in Part Two.
Cooperation: Hiroyuki Ishikawa, President and CEO of Omakase Auto Ishikawa
Official Site
Interviewer/Writer: Komomo Editor: Kuju Illustration: Watanabeko