Should You Read the Inner or Outer Scale on a Tire Pressure Gauge?
3 Answers
Tire pressure gauges can display readings on both the inner and outer scales, but the units of measurement differ between them. The inner scale uses bar as its unit, while the outer scale uses kPa or psi. According to the international standard GBT2978-2008, the recommended tire pressures for different types of tires are as follows: Standard tires: 2.4-2.5 bar; Reinforced tires: 2.8-2.9 bar; Maximum pressure: should not exceed 3.5 bar. Hazards of overinflated tires: Reduced tire friction and adhesion, affecting braking performance; Causes steering wheel vibration and veering, reducing driving comfort; Accelerates wear on the central tread pattern, shortening tire lifespan. Hazards of underinflated tires: Increases friction coefficient with the road surface, leading to higher fuel consumption; Creates heavy steering and veering tendencies, compromising driving safety; Increases movement in various parts of the tire, causing abnormal heat buildup due to excessive compression.
I've been driving for over 20 years, and every time I use a tire pressure gauge, I always check the inner scale because it's in psi units, just like the recommended tire pressure range in the manual for my American SUV, which is marked in psi. The outer scale is in bar units, more commonly used in European cars, but I'm used to the inner scale—it's so convenient. I remember one time when the tire pressure was too low and I didn't adjust it in time, I almost had a blowout on the highway, and my fuel consumption skyrocketed. Since then, I've made it a habit to check my tire pressure every month. Tire pressure is incredibly important—it affects handling, fuel efficiency, and tire lifespan. I recommend all car owners refer to their vehicle's owner's manual to find the correct unit for measurement, and take readings when the tires are cold for better accuracy. Don't underestimate this detail—safe driving starts with basic maintenance.
As an average car owner, I was quite confused about how to read a tire pressure gauge when I first started driving, but later learned that the inner scale shows psi while the outer scale displays bar. I mainly use the inner psi scale now because I often drive Japanese cars in the city, and the owner's manual specifies standard tire pressure in psi. Which scale to read depends on your car brand and preferred unit—just don't guess randomly. Incorrect tire pressure affects braking distance and ride comfort, so I recommend spending more time checking tire pressure in your garage rather than relying on gas station equipment. By the way, tire pressure also impacts environmental protection; maintaining recommended values saves fuel.
