Tire Pressures Revisited

I was online the other night and was part of a conversation related to tire pressures that really brought home how active this topic still is. The actual quote was “My daddy told me to always put the tire pressure to the number on the side of the tire. My daddy didn’t raise no car fool.”

Unfortunately, “Daddy” was wrong. We run across this type of thing a lot- people remember a datum from a long time ago, given by someone who is not a professional, and it’s stuck. Cars, their tires, their maintenance, all of these things have been changing at a rapid pace for many years. We go to dozens of classes each year specifically to keep up with these changes. That being said- listen to us!

Setting your tire pressures is a remarkably misunderstood topic for many people, so I’m going to give you the straight info. The key is remembering that tire manufacturers and auto manufacturers have slightly different interests when calculating and advertising recommended pressures. You want to follow what the AUTOMAKER says. You own a car, not just some tires.

The vehicle manufacturer will put their recommended tire pressures on a sticker located in the driver door jamb and in the owners manual. IN MOST CASES THIS IS THE NUMBER YOU WANT TO USE. The vehicle manufacturer takes into account the weight of the vehicle, what ride quality is required, and the suspension geometry of the vehicle. On most PASSENGER CARS this number will be between 28-35 psi. Light trucks have a whole different set of operating parameters depending on the amount of weight the vehicle will be carrying.

Tire manufacturers will put their MAXIMUM recommended pressure on the sidewall of the tire. This is NOT the optimum number, and usually operating with the tires at this pressure will result in poor ride quality, reduced traction, and reduced tire life. Tires manufacturers make tires, and usually there are a variety of vehicles that will use the same tire size so the tire manufacturer cannot issue a recommended pressure for your vehicle specific application. DO NOT EXCEED THE MAXIMUM PRESSURE STAMPED ON THE TIRE FOR ANY REASON.

My personal recommendation is to use the tire pressure numbers inside the driver’s door or vehicle owners manual.
Some Tips to make life easier:

  • Get a DIGITAL tire pressure gauge from an auto parts store and use that. The “stick type” gauges are very inaccurate, and the ones attached to the hose at the gas station are the worst. If that’s all you have, well, you have to make do with what you’ve got, but you can get a digital tire pressure gauge for less than $15 and it’s accurate and easy to use.
  • Set all your tire pressures at the same time. The relative humidity and ambient temperature has a SLIGHT effect on how the tire pressure will change as the tire heats up and cools down through driving. Set them all to the correct numbers at once.
  • DON’T rely on how your tires “look”. A properly inflated radial tire will frequently look low. Use that fancy gauge thingy in part 1- that’s what it’s for.
  • DON’T over inflate your tires. This causes excessive wear, reduced traction, and loss of ride quality just like tires that are too low.

If all else fails We’ll set you tire pressures for free- just stop by!

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