What is the appropriate tire pressure for a car's spare tire?
2 Answers
The air pressure of the spare tire should be between 2.3bar and 2.5bar. While driving, if the tire pressure is too high or too low, or if the tire encounters sharp objects, the car tire may experience a blowout. Hazards of low tire pressure: Increased friction coefficient with the road surface, leading to higher fuel consumption; Causes the steering wheel to feel heavy and may lead to deviations, which are factors detrimental to driving safety; Increases the movement of various parts of the tire, causing excessive rolling and abnormal heat generation; Reduces the functionality of the cords and rubber, leading to delamination or cord breakage, and excessive friction with the rim, causing damage to the bead area and abnormal wear; Multiplies the friction between the tire and the ground, rapidly increasing tire temperature, softening the tire, and drastically reducing its strength. High-speed driving may result in a blowout; Increases tire body deformation, making the tire side prone to cracks, and generates flexing motion, leading to excessive heat, accelerating rubber aging, fatigue of the cord layer, and cord breakage. It also increases the tire's contact area with the ground, accelerating shoulder wear. Hazards of high tire pressure: Reduces the tire's friction and adhesion, affecting braking performance; Causes steering wheel vibration and deviation, reducing driving comfort; Accelerates wear on the central tread pattern of the tire, shortening its lifespan; Increases vehicle body vibration, indirectly affecting the lifespan of other components; Causes excessive stretching and deformation of the tire cords, reducing the tire body's elasticity and increasing the load on the car during driving; Decreases puncture resistance. When encountering sharp objects like nails or glass on the road, they can easily penetrate the tire, causing internal cracks and blowouts due to impact.
Last time I had a flat tire on the highway, I realized the spare tire pressure was only 3.5 bar after changing it, making the drive extremely unstable and nearly causing an accident. Later, I checked the manual and found that spare tires generally require 4.5 to 6.0 bar, depending on the vehicle model. For example, compact spare tires like mine for small cars require 5.0 bar. Spare tires aren't for regular use; higher pressure helps maintain shape and prevent deformation, making them suitable for temporary use over a few dozen kilometers. Too low pressure is unsafe, increasing the risk of skidding during turns; too high may warp the wheel rim. Now, I use a portable pressure gauge to check my spare tire's pressure monthly, keeping it at the recommended level, and record it in my phone notes. If you're lazy, just ask the technician to check it during each maintenance—don't wait until an emergency to realize it's unusable. Though spare tires aren't used often, maintaining proper high pressure is what responsible car owners do.
