**AMENDED - Version 2 please disregard prior submission **

Because many operators feel that "more is better". More air in the tires, a brighter TV picture, etc.

I myself allow up to 1-2psi above the pressure listed by the car mfg, particularly for winter. But no more.

I sometimes wish that tire mfgs would leave the maximum inflat. value off the tire sidewall, to discourage operators from referencing it when maintaining their tires. That maximum value just provides a "canvas", of sorts, for a wide variety of applications. The same make and model of tire, with a max. inflat. value of 51psi, might see service under anything from a Ford Fiesta to a large Honda Pilot. Of course, the size and aspect ratio of that make & model tire will be different for those two examples, as well as the cold inflation pressure specified for each.

It's also critical to follow, at least closely, any 'offset' pressure requirements, EG, the GM Corvair, in its day, specified an 11psi offset from front to rear cold inflation(F: 15psi, R: 26). Those numbers represent values suitable for the non-radial bias ply tires of 50-60 years ago.

Today, many performance-oriented vehicles, such as from Porsche, BMW, and even Volvo, recommend different front and rear cold pressures. Those pressures were arrived at via hours, and even weeks, of combined calculations, road tests, tread wear and pyrometer analysis, coupled with the goal of arriving at pressures that are the best compromise between load capacity, handling, and comfort.

Varying from those pressures, EG: inflating all four tires to 40psi when only 34 might be specified in front, and 38 in back, or, inflating more than 2psi over or under the pressures in general, EG: 30 or 40psi on a vehicle calling for 33psi at all four corners, might cause unexpected results during even ordinary day driving.

Tires manufactured since 2000 are among the most advanced and safest in world automotive history, and are quite resilient and forgiving of even egregious pressure variations, up to 10psi above or below vehicle requirements, short term. And I emphasize short term, because, not just for wear to the tires themselves, but for reasons of vehicle safety and handling, such pressures should be corrected within a reasonable time of being noticed.

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For full context, visit https://www.motorsforum.com/tech/tire-pressure-77070-.htm