What is the 3% rule for tires?
It’s called the “3 percent rule. Essentially, the rule states that the overall diameter of the new tire on the wheel should be within three percent of stock tire and wheel’s diameter. Bear in mind that the tire width and sidewall height are inversely proportional. This second number actually represents the height of the sidewall expressed as a percentage of the width of the tire. So in our example image, this tire has a width of 235 millimeters, and the 55 indicates that the tire height is 55% of the width or 129.
What’s the best tire pressure?
Running your tires at the correct pressure is important because it keeps you safe, cuts down your gas bill, and makes your tires last longer. Each vehicle has its own specifications for tire pressure, but most fall between 28 and 36 PSI (pounds per square inch). No, for most cars a tire pressure of 40 psi is too high. You might find 40 psi suitable for some vehicles, especially if they’re carrying heavier loads or if the manufacturer’s recommendation is close to that figure. However, it’s generally too high for most passenger cars, which usually recommend between 30-35 psi.Higher pressures (40PSI and higher) should be reserved for high-speed driving (at the racetrack, typically). The ride on the road will be hard and uncomfortable, and a vehicle with pressures set so high might exhibit premature signs of uneven tyre wear, leading to earlier replacement.No, for most cars a tire pressure of 40 psi is too high. You might find 40 psi suitable for some vehicles, especially if they’re carrying heavier loads or if the manufacturer’s recommendation is close to that figure. However, it’s generally too high for most passenger cars, which usually recommend between 30-35 psi.