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If you have ever had a flat tire, you know how frustrating and inconvenient it can be. Luckily, most cars come with a spare tire to help you get back on the road until you can fix or replace the damaged one. But have you ever wondered why spare tires have higher PSI than regular tires? This article will explain what PSI is, why spare tires have higher PSI, and how to properly check and maintain your spare tire.
What is PSI and Why Does It Matter?
The unit of measurement for air pressure is PSI, or pounds per square inch. Air pressure is the force exerted by the air molecules inside a tire on the tire walls. The higher the air pressure, the more rigid and inflated the tire is. The lower the air pressure, the more flexible and deflated the tire is.
Air pressure is essential for several reasons:
Why Do Spare Tires Have Higher PSI?
Now that you know what PSI is and why it matters, let’s answer the central question: why do spare tires have higher PSI than regular tires? The answer depends on the type of spare tire you have. There are two main spare tire types: donut spare tires and full-size spare tires.
Donut Spare Tires
Donut spare tires, compact or temporary spare tires, are smaller and thinner than regular tires. They save space and weight in your trunk and serve as an emergency solution. Please only use them for short distances or low speeds.
Because of their smaller size, donut spare tires need higher PSI to support the weight of your car. The recommended PSI for donut spare tires is usually around 60 PSI, almost twice as much as regular tires. This higher pressure gives them more stability and control for short-term use. However, it also makes them more prone to overheating and blowouts. Do not drive them for more than 70 miles or exceed 50 mph. Replace them promptly with a regular tire.
Full-Size Spare Tires
Full-size spare tires, or conventional or permanent spare tires, are the same size and shape as regular tires. They can replace any of your standard tires and last just as long. Typically, larger vehicles like trucks or SUVs have them, offering more trunk space and weight capacity.
Because of their standard size, full-size spare tires do not need higher PSI than regular tires. The recommended PSI for full-size spare tires is usually the same as that for common tires, typically between 32 and 38 PSI. This normal pressure gives them the same performance and durability as regular tires. However, it also means they take up more space and weight in your trunk, which might affect fuel efficiency and cargo capacity.
How to Check and Maintain Your Spare Tire Properly
Regardless of your spare tire type, you should always check and maintain it properly. Here are some tips on how to do that:
- Check the PSI of your spare tire regularly, at least once a month, or every time you rotate your tires. Use a tire pressure gauge to find out the PSI of your spare tire. To do that, locate the valve stem on your spare tire, unscrew the cap, press the gauge against the valve stem, and read the PSI on the meter. If the PSI is too low or too high, adjust it accordingly using an air compressor or a tire inflator. You can find the recommended PSI for your spare tire on the tire sidewall, either on the sticker inside the driver’s door or in the owner’s manual.
- Check the situation of your spare tire regularly, at least once a year or every time you use it. You can use your eyes and hands to inspect the condition of your spare tire. To do that, look for any signs of damage, such as cracks, bulges, punctures, or wear. If you find any, replace your spare tire as soon as possible. You can also scan the tread depth of your spare tire using a penny or a tread depth gauge. To do that, insert the penny or the meter into the tread grooves of your spare tire. If you can see the top of Lincoln’s head on the penny or the gauge reads less than 2/32 of an inch, your spare tire is worn out and needs to be replaced.
- Store your spare tire properly in a cold, dry space and away from direct sunlight and heat sources. You can use an extra tire cover to protect your spare tire from dust, dirt, and moisture. You can also use a spare tire carrier or a spare tire mount to secure your spare tire in your trunk or under your car. Doing this can stop your spare tire from shifting and breaking down while driving.
Spare tires are lifesavers when you have a flat tire, but are not the same as regular tires. Depending on your spare tire type, you might need to inflate it to a higher PSI than standard tires. It’s so because donut spare tires are smaller and require more pressure to support the weight of your car, while full-size spare tires are common and need the same pressure as regular tires. To confirm the safety and performance of your spare tire, you should always check and maintain it properly. By following these tips, you can make the most of your spare tire and get back on the road safely and smoothly.