Why Can't a Spare Tire Be Used as a Regular Tire?
3 Answers
Spare tires cannot be used as regular tires for the following reasons: spare tires have different friction coefficients, ground adhesion, and air pressure compared to other tires. Prolonged use can affect the vehicle's braking system, steering system, and suspension system, posing significant safety hazards. Additionally, since spare tires and original tires are manufactured at different times, their aging, hardening, lifespan, and deformation vary. Therefore, long-term use is unsafe. Spare tires should be replaced with original tires as soon as possible after emergency use. Moreover, regardless of their width, spare tires have specific production and usage requirements set by manufacturers. Since spare tires are not used regularly, they do not experience wear. Using a brand-new tire alongside heavily worn tires can create safety risks. Currently, there are three internationally recognized types of spare tires: the first type is identical to the regular tire, known as a full-size spare; the second is a non-full-size spare, commonly referred to as a narrow tire, usually smaller in size; the third is a folding spare tire, which is stored folded in the trunk and inflated when needed for emergency use. The difference in size between spare tires and regular tires is primarily for safety reasons. Since car tires inevitably wear over time, even if a spare tire is of normal size, the difference in wear between the spare and the other tires can create safety hazards. To discourage long-term use of spare tires, manufacturers intentionally make spare tires smaller to prompt drivers to replace them with regular tires promptly. Spare tires also require maintenance: Regular inspections are necessary because spare tires are rarely used and often overlooked. When needed, drivers may find the spare tire flat or cracked, leading to significant issues. Avoid oil contamination. Oil products should not be stored with spare tires, as rubber, the main component of tires, is highly susceptible to damage from oil exposure. Some externally mounted spare tires are exposed to harsh weather conditions, which may shorten their lifespan.
A spare tire cannot be used as a regular tire primarily because it is designed only for temporary emergency use. I once used one, and the speed was limited to 80 km/h—exceeding this could easily lead to danger. The size and tire pressure of a spare tire often differ from the original tire. For instance, many cars come with a compact spare tire that has a much narrower tread, making handling unstable at higher speeds, especially when turning on wet or slippery roads where insufficient grip may cause the car to skid. Additionally, the material of a spare tire is less durable; the rubber tends to age and crack over time, and prolonged use at high speeds will inevitably lead to a blowout. Long-term use can also cause uneven stress on other tires, accelerating wear and even damaging the suspension system. Therefore, manufacturers emphasize that after installing a spare tire, you should repair or replace the original tire as soon as possible, driving no more than a few dozen kilometers before stopping. Remember, safety comes first—don’t risk your life to save money or effort, as even a dashcam can’t capture these unexpected moments.
As a car owner, I only realized how unsuitable spare tires are for daily replacement after trying one. Spare tires are designed with weight and specifications aimed at saving space, such as foldable or narrow tires, which noticeably increase noise and cause bumpy rides. They come with strict speed limits—exceeding them leads to instability and affects braking distance. Their durability is also poor, with simpler rubber composition and structure making them prone to punctures. Long-term use can damage the balance of the chassis system and increase fuel consumption. More importantly, managing tire pressure is troublesome, as spare tires often require higher pressure, and forgetting to check can lead to leaks mid-journey, making things worse. It's recommended to repair the original tire immediately after temporary use; otherwise, it can negatively impact the vehicle's overall lifespan.
