Tire - pressure gauge - wikipedia Tire - pressure gauge A tire - pressure gauge in use. The example in this image is a Bourdon tube gauge. A tire - pressure gauge, or tyre - pressure gauge, is a pressure gauge used to measure the pressure of tires on a vehicle. Since tires are rated for specific loads at certain pressure, it is important to keep the pressure of the tire at the optimal amount. Tires are rated for their optimal pressure when cold, meaning before the tire has been driven on for the day and allowed to heat up, which ultimately changes the internal pressure of the tire due to the expansion of gases. The precision of a typical mechanical gauge as shown is ± 3 psi ( 21 kPa ). Higher precision gauges with ± 1 psi ( 6.9 kPa ) uncertainty can also be obtained. Contents 1 Built - in tire pressure sensors 2 Regulations on tire pressure 3 References 4 External links Built - in tire pressure sensors Many modern cars now come with built - in tire pressure sensors that allow all four tire pressures to be read simultaneously from inside the car. In 2005, most on - board Tire Pressure Monitoring Systems ( TPMS ) used indirect pressure monitoring. The anti-lock brake sensors detect one tire rotating faster than the rest and indicate a low tire pressure to the driver. The problem with this method was that if tires all lost the same pressure then none would show up against the others to indicate a problem. Regulations on tire pressure Since September 2007 all new automobiles below 10,000 lb ( 4,500 kg ) in weight sold in the United States are required to incorporate a Tire Pressure Monitoring System, which is capable of monitoring all four tires and simultaneously reporting under - inflation of 25 percent of cold placard pressures in any combination of all four tires. TPMS known as Direct TPMS are capable of TREAD Act legislation requiring simultaneous pressure measurement for each tire pressure. Early TPMS sensors required batteries, but the latest TPMS technology eliminates all sensor batteries. References Jump up ^ http://www.nhtsa.dot.gov/cars/testing/ncap/Tyres/pages/TPandLoading.htm Jump up ^ http://etv.com.au External links Wikimedia Commons has media related to Tyre pressure gauges. Retrieved from `` https://en.wikipedia.org/w/index.php?title=Tire-pressure_gauge&oldid=807310838 '' Categories : Tires Pressure gauges Hidden categories : Commons category without a link on Wikidata Talk Contents About Wikipedia Nederlands Edit links This page was last edited on 27 October 2017, at 05 : 10. About Wikipedia

Question: instrument used to measure air pressure in tyres
Answer: tyre-pressure gauge