So let's get it out right up front and be done with it. It's true what your mother told you: Convertibles are very dangerous. A lot of people have never thought of this, but your mother has: Almost any hoodlum standing on the sidewalk next to a convertible that has stopped for a light can whip out his stiletto and stab you right through the top. Then there's the bullet problem: The year of the L.A. freeway shootings is not a great time to own a convertible. The slug exiting one of those .25- caliber glove-compartment pistols is not slowed one whit by a rag top. And, of course, you do not need to be reminded that the Russian space station will not be up there forever: Hot space junk falling on the top of even a parked convertible is a very messy situation to say the least -- convertibles cannot be ordered with flameproof interiors.

Pretty scary what can happen when your top is soft, but it isn't what your mother tells you about convertibles that should make you worry. It's what she doesn't tell you: her fears about how you'll, well, how you'll change. "Bobby was such a nice boy until he bought that convertible," she'll tell her friends.

Take, for example, her hidden fears about the problem of directional stability found in convertibles. Many a convertible owner, cruising comfortably down 16th Street on the way to work, has suddenly found the steering completely awry and the vehicle headed east toward the Bay Bridge on Route 50. The problem, labeled "unintended recreation" by the scientific community, often cannot be overcome by the driver until the car reaches Ocean City, Md.

Research psychologists are only now beginning to discover other possible effects of convertibles on character. For example, early tabulations of a simple test now being given by a team of social scientists to more than 500 buyers of convertibles shows that rag-toppers are more subject to reality denial than are other car owners. When buyers first take possession of their new convertibles, they are asked a slew of questions, including the one that researchers are most interested in: How old are you? Several months later, buyers are asked the same questions again. Invariably, convertible owners list their age as approximately 10 years younger the second time they're asked.

Personality deviations and compulsive behavior in convertible owners have been noted since the 1950s, when almost every car line offered a convertible model -- even Nash. But observers agree that things are getting worse as convertibles become rarer (there are only seven convertibles built in the United States, and you can't afford two of them). For example, a prominent Washington psychotherapist drives every day from the Maryland suburbs to his office in the city with the top down on his Chrysler LeBaron. He survives the heat and humidity of August by putting the car's air conditioner on the coldest setting, blasting it full force and turning the vents so that the cold air smacks him in the face. "If it gets really bad, you can roll up the windows with the top down and trap a lot of cool air," he says. "I call it the bucket effect. The car fills up with cold air like a sand bucket in the surf." (The conversation of most convertible owners is littered with references to the beach.) Indulgent? "It's my car and it feels good," he says. In the winter, he and numerous other fanatics can be seen using the bucket trick in reverse: top down, windows up, heater on full blast.

Apparently, the need among convertible owners to keep the top down becomes more excessive the longer they've owned the vehicle. (It's easy to spot convertible owners who secretly wish they had not bought a convertible -- their tops are almost always up.) The truly psychotic can be separated from the merely neurotic by their rain behavior. The real nuts keep the top down even in the rain. They are able to prevent the interior of the car from becoming an algae bed by always driving faster than 40 miles per hour, which, of course, means running all red lights and stop signs. Therefore, these people are often found commuting via Rock Creek Parkway in bad weather.

To avoid rain damage and to keep from ever having to put the top up, most convertible nuts live in houses with garages, and they back their cars into the garages with the grill facing forward -- they like to be able to race off at a moment's notice. Like the Lone Ranger leaping gracefully into the creaky leather saddle of his trusty steed Silver, the average convertible nut can be seen leaping into the garage, placing his right hand firmly on the door top and vaulting over the side of the vehicle, landing squarely in the driver's seat.

Then off he goes, top down, hair flying in the breeze, a glorious tan, a contented smile, if not a bit of smirk, doing maybe 15 over the limit, into the sunset. FOR A FEW BRIEF YEARS, NEW CON- vertibles and their drivers actually did disappear into the sunset. In April 1976, a Cadillac Eldorado rolled off a Detroit assembly line, and that was that -- the last American convertible to hit the streets. American Motors had stopped building convertibles in 1968, Chrysler in 1971, Ford in 1973. Convertibles had become outdated by cheap air conditioning, workable sunroofs and what car manufacturers perceived in buyers as the search for a rattle-free, quiet ride. (Modern convertibles, because they lack the structural support of a metal roof and are not built on significantly heavier chassis than sedans, are as a group among the noisiest, most vibration-prone autos ever made.)

The truth of the matter is that the explanations American auto manufacturers have given for ceasing to build convertibles have never made much sense. It's hard to believe that convertible nuts were really satisfied with hardtops, moonroofs and canvas pasted over metal roofs to make them look like convertibles. It's easy to believe that convertible nuts became as disgusted as anyone by the quality of American cars in the 1970s, and that they became frustrated by the apparent refusal of the Japanese to export convertibles. It's easiest of all to believe that Americans got exactly what Detroit wanted to give them -- or not give them -- and their desires be damned.

The man who ruined what your mother saw as a good thing -- the end of convertibles -- was Lee Iacocca, the father of the Mustang and the savior of Chrysler. When he was shown a full mock-up in the early 1980s of a sketch of how the new Chrysler LeBaron might look as a convertible, he told his staff: "Build it. We'll sell it."

Chrysler moved slowly at first, telling dealers it would build the car only if it had advance orders. The company hoped demand would be high enough to build about 3,000 cars in 1982. It was flabbergasted when nearly 4,000 advance orders poured into Detroit as soon as the new car was announced.

"We started the convertible comeback," says Joseph A. Campana, Chrysler's vice president of marketing, and the company has been wildly successful with them. Last year Chrysler sold 37,000 rag tops --

only about 2 percent of overall sales, but an extraordinary number when you consider that these are cars that were not designed to be convertibles in the first place, that a Chrysler "convertible" coming down the assembly line was actually a sedan. To make it a convertible, someone had to saw off its top.

That changed this year. The 1987 LeBaron convertible was designed from the wheels up as both a coupe and a convertible. And if Chrysler is even more successful with this car, the blame can clearly be laid at the feet of Campana. "I love convertibles," he says. "My first car was a convertible. I had convertibles before I got into the auto business. Ever since I've been in the auto business, I've tried to get convertibles to drive . . . A convertible represents the truest expression of the love affair between a driver and a car. The person who buys a convertible buys it because of the way it makes him feel about himself . . . the statement it makes. People don't buy convertibles for transportation."

Campana, if you hadn't guessed, is just like all the rest of them. After a hard day at Chrysler corporate, he will put the top down on his new LeBaron, hit the local interstate and bring his speed up to "between 55 and 65 miles per hour." At this point, he looks up at the sky. If it looks like rain, he may chuckle to himself. "The aerodynamics on this new convertible are so good that you can drive through a moderate rain without getting wet," he says with glee. "What's really interesting, though, is seeing the expressions on the other drivers' faces. They think I'm some kind of nut."

It makes you wonder: Where is this guy's mother? :: WHAT PRICE OPEN AIR?

Sometimes Esteban Milla cannot believe what he sees rolling into his narrow little garage in Kensington where he replaces the tops on convertibles.

"Sayvehn-thousan dohlars," he says, the words thick with his Peruvian accent. He shakes his head from side to side. "Sayvehn thousan dohlars," he repeats for emphasis, "for a Volkswagen." He stares at a Volkswagen Bug convertible, stripped bare of its canvas, the skeletal steel frame of the folding roof looking like a heavy spider web over a decayed car. The man who brought the car in, Milla says, was "happy to have got the car for sayvehn thousan dohlars."

Milla cannot believe how much money people pay for "junk" just because it's a convertible. Worse, he almost feels guilty telling them how much more they'll have to spend to keep the snow out. A new top for a Volkswagen, for example, can easily cost $1,000, and that's if the top is vinyl. You want genuine West German canvas? Eighty-five bucks a yard and highly recommended by Milla: "doesn't stretch." With West German canvas, the top could cost $2,000. Heaven help you if the Volkswagen is pre-1973. Then you may have to replace a rotted wood frame around the back window ($400) or a rotted wood bow frame at the front of the top ($265).

Got a 1982 to 1986 Chrysler or Dodge convertible? All of the ones Milla has been asked to fix have little tears at the back of the roofline. So do a lot of late 1960s and early 1970s General Motors cars he sees. Is the metal frame for your top too rusted? Many are no longer made, and junkyards get about as much as they want for them -- if they have them at all.

As for the replacement tops and parts themselves? "Not as good as they used to be," Milla says. "The vinyl, it's not as good; the rubber, it's not as good; the motor's not as good. Everything is cheaper now, made to last less. Always, the original top lasts longer than the replacement."

Not long ago a man brought in a Mustang convertible for a new top. "The customer had already invested $11,000 in it," Milla says. "He took pictures of me putting a new top on." Craziness, says Milla.

And what does Milla drive? "A 1966 Chevrolet convertible. A wonderful car!"