Why can't the total mileage of a spare tire exceed 100 kilometers?
4 Answers
It depends on whether it's a full-size spare tire or a compact spare tire. If it's a compact spare tire, it is designed for short-term emergency use only, with lower specifications and speed ratings, so the speed generally should not exceed 80 km/h. Full-size spare tire: A full-size spare tire has exactly the same specifications as the other four tires on the vehicle and can replace any temporarily or permanently unusable tire. Compact spare tire: This type of spare tire has a slightly smaller diameter and width compared to the other four tires, so it can only be used as a temporary replacement and must be installed on non-driving wheels. Additionally, the maximum speed should not exceed 80 km/h.
Once when I was on a long drive using the spare tire, the mechanic specifically warned me to replace it within 80 kilometers at most. The spare tire is thinner than regular tires, with a different rubber compound, primarily designed for emergencies. Standard tires have 7 reinforced cord plies on the sidewalls, while spares only have 2 layers—prolonged driving can cause the rubber to overheat and soften. The tire width is over 20% narrower, reducing grip during sharp turns and increasing the risk of skidding. Most critically, the tire pressure system isn't compatible; extended use can easily deform the wheel rim, and repairing a rim costs far more than replacing a spare. My neighbor once insisted on driving 150 kilometers with it, resulting in complete failure of both the wheel hub and bearings, costing nearly 5,000 yuan in repairs.
A colleague drove on the spare tire for three days after a flat before getting it repaired, and ended up getting lectured by the 4S dealership. Their workshop manager explained that spare tires are designed for single trips—exceeding 100 kilometers causes the internal steel belts to loosen, with tread temperatures reaching 90°C. While regular tires undergo dynamic balance testing for up to 80,000 kilometers, spare tires only endure 30-hour durability tests. Moreover, non-full-size spares are smaller, and prolonged use can lead to abnormal wear on the transmission differential gears. Replacing a differential costs over 20,000 RMB—definitely not worth the minor savings in mileage.
When my friend was changing the spare tire at the highway service area, the traffic police specifically warned not to exceed 80 km/h for 100 kilometers. Regular tires have anti-slip grooves on the tread, while spare tires only have a few shallow grooves, resulting in a braking distance that's 5-6 meters longer in rainy conditions. Those narrow tires marked T125 lack sufficient centrifugal force when turning, and the car body starts to sway at higher speeds. The rubber compound is also designed only for 60°C, making it prone to delamination when the road temperature reaches 70°C in summer. The worst case I've seen was a spare tire blowing out and damaging the wheel arch, costing 3,000 just for repainting.
