Recommended psi and maximum psi are two very different things when it comes to air pressure.

Dear Car Talk

Dear Car Talk | Jul 01, 2004

Dear Tom and Ray:

It happened again! I get my oil changed at Jiffy Lube, and they inflate my tires to just under the maximum pressure indicated on the tire (42 psi, max 44). I tell them that's wrong, that you should go by the driver's-door placard (28 psi), and the bozo argues with me! Then he says it's Jiffy Lube policy, and I'm starting to think it might be, given my experience. I've seen this three times and argued with different guys at two different Jiffy Lube outlets about this. I'm thinking I should call "60 Minutes" and get Mike Wallace on this, but I thought I'd try you guys first. Apparently there's a huge amount of ignorance out there about tires. -- Ken

RAY: There certainly IS a lot of confusion about proper tire inflation, Ken. So we called Alan Greenspan, the nation's foremost authority on inflation.

TOM: But he just issued some murky parables and told us to get lost. So, we'll have to clear this up ourselves.

RAY: "Maximum" and "recommended" tire pressure are two different things. Maximum is the greatest amount of pressure the tire can safely hold, before it's in danger of exploding. That's the number you should never, ever exceed, no matter what.

TOM: "Recommended" tire pressure (which is usually listed on a placard on the driver's doorjamb, or on the glove-compartment door) is what the manufacturer says is the best pressure for all of your normal driving. That's the number to use when inflating your tires.

RAY: Take sleep as an analogy. What's the maximum number of hours you can sleep? Who knows? Maybe it's 12 or 18 hours. For my teenage son, it could be days. But the recommended amount of sleep is more like eight hours. That's a more meaningful number if you want advice on how much sleep to shoot for.

TOM: If you inflate your tires to or near the maximum -- as this bozo did --you can really wreak havoc on the car's handling and braking, particularly in wet weather. It's a serious safety issue. You'll also cause the tires to wear improperly.

RAY: And worst of all, you'll be tying up the emergency room. When the tires are overinflated, the vehicle really bounces around, leading the driver and passengers to get welts on their heads from hitting the ceiling.

TOM: And this is not Jiffy Lube policy, Ken. We called the company to confirm that. Jiffy Lube stores are run by independent franchisees, so it's not easy for the folks at corporate headquarters to police each and every bozo who owns a store. This guy clearly made up the "Jiffy Lube policy" line to get rid of you. And maybe the same guy owns several franchises in your area, which is why you keep running into this.

RAY: Show him this article, Ken. Let's hope he gets the message before he causes someone to have an accident. Or another welt.

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