Attach a pointer, and as the tube unwinds you’ll get a pressure reading. The principle is that a flattened, curved tube will try to straighten when pressurized. Usually offer only two measurement scalesĪlso called analog tire pressure gauges, these used to be seen only in commercial environments but are now widely available. Questionable accuracy (We could not find one with American National Standards Institute certification.) You read the tire pressure off the rod nearest the end of the body of the gauge.Ĭan reach inner tires on commercial vehicles and trucks with dual tire setups (large versions with twin heads) The higher the pressure, the more of the rod appears.
A calibrated rod is attached to the piston, and the air forces a certain amount of the rod out of the end of the body. These gauges have been around almost as long as tires! When pressed onto a tire valve, escaping air forces a piston down the main body of the gauge. Kilograms per centimeter squared (kg/cm2) is another European system. Kilopascals (kPa) is a European standard that isn’t widely used. Pounds per square inch (psi) is the most common.Ītmospheric air pressure (bar) is equal to the pressure felt at sea level. Depending on the gauge you buy, it will measure in one or more of these: There are four pressure measurements you’ll see on tire gauges. There are three main types of tire pressure gauge: pencil (also called stick or rod gauges), mechanical dial, and digital. The center wears out more quickly than the edges.
Tire’s contact patch wears out: A smaller contact patch (or footprint) means weight isn’t distributed properly. Tires lose grip: When tires “round out,” less rubber is in contact with the road, reducing grip. Department of Motor Vehicles (DMV) gives figures of 0.2% more fuel for every pound per square inch of under-inflation. Tires overheat: The overheating of a tire can lead to the tread section separating from the casing (or carcass), resulting in a blowout.Ĭar handling worsens: While traction might actually increase slightly, the sidewalls aren’t doing their job properly so handling suffers and you can’t stop as quickly.Ĭar uses more fuel: Incorrect inflation increases fuel consumption. Tires wear out: More of the rubber is in contact with the road, so your tires wear more quickly. Warnings can sound overly dramatic, but tires with too little or too much air can lead to numerous problems. The only accurate way to measure tires is with a good-quality tire pressure gauge. Off-road vehicle tires in particular often seem a little soft. You can’t tell if a tire needs air just by looking at it.