Dear Tom and Ray:

I was wondering if you could answer another question about driving on the beach. I have a permit that allows me to drive on the nearby beaches, and to be able to drive on the beach, you must first let some air out of each tire to give you better traction. The National Park Service recommends 12 psi. Of course, as you said in a previous column, as soon as you get off the beach, you have to refill the tires to avoid tire damage on normal roads. My question is, does lowering the pressure and then filling the tires back up affect tire balance? -- Virgil

Ray: Sure. If all the nitrogen molecules, which are lighter, ended up on one side of the tire, and all the argon molecules, which are heavier, ended up on the other, the tire could end up seriously out of balance.

Tom: Don't listen to my brother, Virgil. He barely graduated from the Massachusetts Institute of Technology with a degree in Humanities. The answer is no. Adding or removing air from a tire will have no effect whatsoever on wheel balance.

Ray: Unless you accidentally whack off a weight with the end of the air filler hose while you're refilling it.

Wait! Don't buy another car without the mechanic's checklist that's included in Tom and Ray's pamphlet "How to Buy a Great Used Car: Secrets Only Your Mechanic Knows." It will help you get a good used car and avoid the clunkers. To order, send (check or money order) to Ruin, P.O. Box 536475, Orlando, FL 32853-6475. You can also order online.

© 1999 by Tom and Ray Magliozzi and Doug Berman Distributed by King Features Syndicate, Inc.

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