High-Tech Old-School Luxury ; Lexus flagship comforts its occupants without wallowing on the road.

It doesn't take long behind the wheel of a Lexus LS 430 to recognize it as a traditional luxury car. The key attribute is isola-tion from the outside world; it's a stress-reduction therapy chamber on wheels. Think ``serenity.''

Nor does it take long at the track to recognize that serenity is not incompatible with performance: The Lexus LS 430 accelerates to 60 mph in under 6.5 seconds and stops from 60 mph in 117 feet, decent benchmarks for a sport sedan, let alone an isolation booth.

The Sport model tested corners at 0.81 g and averages 42 mph through our tight slalom-better than what we've recorded in midsize domestics like the Taurus and Monte Carlo. On the one hand, those are middle-of-the-road numbers for a car in the $70,000 class; on the other, high g loads and quick maneuvers aren't likely to appear in the LS 430 driver's playbook. With this much power, there's no real need to run the freeway on-ramp very hard, because the silky smooth, amazingly quiet V8 does a more than ample job merging.

It was the braking performance that most astonished our testers. A 3955-pound sedan on tires chosen as much for their comfort and low-noise qualities as for grip and performance is likely to need 130 feet or better to come to a stop, experience suggests. The Mercedes-Benz S500 we test-ed in 1999 took 137 feet to do it, autobahn-tuned brakes and all. ``This car has no right to stop like this,'' said our wheelman of the LS 430, mystified.

If the LS 430 is all about serene motoring, though, good brakes are an excellent idea. This is the box for which the expression ``all the toys'' was invented, and one of those toys is radar cruise control, which maintains a set following distance from the car ahead. If you're going to rely on that, you want good brakes. Other toys are GPS navigation system, voice recognition, parking warning detector, theater-quality sound and a wide array of gizmos and geegaws that can include massaging seats and refrigeration units. We won't say the LS 430 driver is more likely than anyone to be distracted from the task of driving, because that's a choice drivers make individually. Cell phone-chattering, burger-chomping drivers cross socioeconomic and marque-preference boundaries as often as they ...