Dear Tom and Ray:

My third, black Mercury Grand Marquis, "Batmobile," is a 2002 with 80,000 miles on it. Yesterday my dealer told me that the air bags have aged -- lost their elasticity, inflatability and verve. My mind leapt to my 62-year-old breasts as the service manager described the problem. If they were not replaced, he said, one day I would see my car riding very low and hear the pump, which inflates the bags, running hopelessly. The cost of replacing these bags is 1,200 dollars. I plan to keep the car at least another two years. A good new bra is 30 bucks. That's a big difference. What is your advice? Shall I make the repair?

-- Fee

TOM: 1,200 dollars is a lot of money, Fee. That's 40 bras.

RAY: The air bags your dealer is talking about are not the driver and passenger air bags that protect you in an accident; they're the rubber air bladders that serve as springs in this car's air suspension system.

TOM: That's what gives you that pillowy, tush-coddling ride you know and love. But it has a downside.

RAY: Over time, the rubber degrades and starts to leak, and then the air pump has to run more and more frequently to try to keep the bladders inflated. In the worst-case scenario, one or more of the bladders fails completely, and it'll be like driving without springs.

TOM: But if the dealer is just warning you that they're starting to wear out, and he's suggesting that you replace them in advance of any problem, I'd hold off. They may degrade slowly enough that your problems during the next two years will be minimal, or even nonexistent.

RAY: If the bladders are actually leaking, then you have a couple of choices: You either can pony up the big bucks and pay the dealer for a whole new system, or you can replace the system with a more traditional set of springs.

TOM: There are "conversion kits" available for cars with air suspension systems. Why? Because when people find out they have to fork over 1,200 dollars for a new system, they freak out.

RAY: So your other option is to find an independent shop you like (try searching at www.cartalk.com/mechanics), and ask a mechanic there to give you a price on the purchase and installation of a conversion kit. It'll still cost you hundreds, but at least you'll be able to afford underwear. Good luck, Fee.