QDear Tom and Ray:

It happened again! I get my oil changed, 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! Apparently there's a huge amount of ignorance out there about tires. -- Ken

ARAY: 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.

Dear Tom and Ray:

Soon I will be receiving as my first car -- drumroll, please -- a 1993 Buick Roadmaster Station Wagon! My parents have given me permission to decorate it in any way, as long as it does not destroy the "value" of the car. So, as my big design, I decided to cover the wood details with Astroturf, or another substance like it. My question: What can I use to keep the Astroturf on the car? It would need to be windproof, waterproof and removable. When it needs to be removed, it cannot damage the "paint job." Thanks. -- Aaron

TOM: Well, your parents are very lucky, Aaron. My kid's first move would have been to try to lay a Sealy Posturepedic in the back of the wagon. So Astroturf sounds wonderfully innocent to me.

RAY: Unfortunately, this is not an easy problem to solve. Big sheets of Astroturf are pretty heavy. You have to make good and sure they're not going to fly off while you're driving. If a guy driving behind you suddenly gets his windshield covered with an Astroturf doormat at 60 mph, he's likely to have an accident. And then -- rightfully -- come after you with a baseball bat. And a lawyer.

TOM: Unfortunately, the adhesives that stick the best are also the most difficult to remove. You can try a contact cement and a release agent, but they're probably going to mar the car's finish. So try it out first in a nice, inconspicuous spot.

RAY: Like on your neighbor's car.

TOM: If that sounds too risky (it does to us, Aaron), you might look into magnetism. There are lots of magnetized decorations you can buy for your car, and those will come off in a snap when Mom and Dad repo the Roadmaster.

Got a question about cars? Write to Click & Clack in care of The Post, or e-mail them by visiting the Car Talk Web site at www.cartalk.com.

(c)2004 by Tom and Ray Magliozzi

and Doug Berman