The previous-generation Mustang, a modified, welded version of a chassis that dated to 1979, was about as stiff as wet rope. Ford claims the current Mustang's body/frame is 31 percent stiffer, and we won't argue. This Mustang is simply much more rigid and rattle-free than its predecessor. A rigid foundation provides the basis for a host of good things, including improved ride quality, sharper handling and less interior vibration.

The new-found solidity even applies to the convertible. It's a fact: Cars that cost five times as much as the Mustang tend to get shakier when the fixed roof is removed to design a convertible version. In the Mustang convertible, you will notice some shimmy in the windshield frame that you'll never see in the coupe. Yet when it comes to overall rigidity, the current Mustang convertible is light years better than its predecessor. Our test car was solid enough to think that it would remain largely rattle-free even after a couple of winters pounding over Midwest roads.

The convertible's folding top is simple and straightforward to operate. Unhook it from the windshield header and it powers back behind the back seat with the touch of the button. The ultimate in posing requires that you manually install the optional boot, but the folded, exposed top and frame don't look too bad without the cover.

It doesn't look it, but the 2006 Mustang has a wheelbase six inches longer than the previous generation, and that makes all the difference. The ride has smoothed out, and the remaining harshness is of a completely different order. The new rear suspension uses coil springs and a lightweight three-link design with a Panhard bar and other locators to keep things constant. It's about as good as a solid axle gets, and greatly reduces skipping and bouncing at the back of the car.

The 4.0-liter V6 engine has more technical sophistication than any previous Ford V6. It's a solid performer for urban, exurban and suburban duties, and the ratios in the five-speed automatic transmission seem well matched to the available torque. When the automatic gets into overdrive fifth gear, the engine goes quietly into economy mode until called upon for a lane change, a pass, or an uphill charge. This is a large-displacement V6 and it sounds more muscular at full throttle than any previous Ford V6 engine.

Indeed, the Mustang V6 Deluxe is the most popular model (about 70 percent of Mustangs sold today are V6s), and we like it. For under $20,000, it delivers good torque, good acceleration and generally good road manners, with a sportier feel then previous six-cylinder Mustangs. Interestingly, while it has 90 fewer horsepower and 80 foot-pounds less grunt than the V8, with smaller tires, the V6 seems slightly more eager to turn and more agile than the nose-heavy Mustang GT (the GT weighs about 150 pounds more, and almost all of that is on the front tires).

One of the biggest improvements in this Mustang is the steering. Its predecessor had a mushy steering feel with a large dead spot on center, and hard cornering required a leap of faith. This one's steering is more crisp, more precise and more confidence inspiring.

The brakes, too, are improved, 15 percent larger than the previous generation. They work well in high-speed highway driving situations, as we found during a test in Los Angeles. If you want ABS, you will automatically get, and pay for, traction control, which has a dash-mounted off switch for special situations. Like drag racing, for instance.

The GT is a 300-horsepower, five-speed pavement-ripper for about $25,000. The new three-valve V8 engine features both variable camshaft timing and electronic throttle control, with new, smarter, faster-acting engine management electronics. It will run 0-60 mph in about 5.5 seconds, it will outbrake a large number of sporty cars and it handles better on canyon roads that any previous Mustang GT, with a minimum of body roll and a large portion of tire grip.

The GT looks mean, and it drives mean, with 320 pound-feet of torque, a decent shifter and a brawny, loud exhaust note. It's everything a pony car is supposed to be, without the teeth-rattling stiffness of the muscle cars of another era. The Mustang GT also has one of the world's largest aftermarket speed-part networks for those who want even higher performance.