To be honest I was a little worried about the dubs. Giant 21 inch alloys and low profile tires seemed about the last thing Mercedes-Benz's comfortable and capable GL-series SUV needed; pointlessly expensive Beverly Hills bling that would surely prove as useful as a chandelier on the Space Shuttle.

I like the GL-series a lot. It was our 2007 Sport Utility of the Year, and deservedly so. It's the best vehicle Benz builds off the hardware that also supports the ML-class and the R-class, offering just the right mix of roomy functionality (including a third row adults can use, with seats that fold in and out of the floor at the touch of a button), confident road (and off-road) manners, and quiet Mercedes luxury.

The GL550 is the top of a three model GL range for 2010. It boasts a number of minor cosmetic tweaks, including a bolder, deeper grille and LED daylight running lamps up front, and quad exhaust outlets at the back. Under the hood is Benz's muscular and versatile 5.5-liter V-8, which develops 385hp and 391 lb-ft of torque, a useful 75 percent of which is available from just 1000rpm. And then there are those standard-issue dubs: Gorgeous five spoke AMG alloys, shod with meaty 285/40/R21 Continental Cross Contact all-season run-flat tires.

Dubs might look cool, but they add a lot of unsprung weight, as Ron Kiino pointed out a few months back when he tested Ford's Edge Sport, which rolls on giant 22-inchers. More unsprung weight makes it harder for suspension engineers to deliver superior ride quality, as spring and damper rates invariably have to be stiffened to keep the heavier wheels under control. Compounding the problem is the fact bigger diameter wheels also demand lower profile tires with stiffer sidewalls.

Sure enough, I noticed a little edge to the GL550's ride that our long term GL450, fitted with 19-inch wheels and plumper 275/55 tires, never had. Then there was the subtle disconnect between the super-sharp initial response of the low profile Contis and the languid transients you'd expect from a 5313 lb SUV. I was prepared to be annoyed. But in the middle of a 436-mile stint behind the wheel, on a quiet two-lane that alternated from fast open stretches to a yee-hah! roller coaster ride along a twisting, heaving canyon, I learned to love the dubs

The big Benz was more fun down that road than any truck had a right to be. And what made the GL550 impressively quick and composed through the twisties were those massive Contis, which offered a ton of grip, and plenty of mid-corner feel. I flicked the air suspension into sport mode, and made the most of the 385-horse V-8, using the steering wheel mounted paddles to run up and down the seven-speed automatic transmission's ratios, left foot braking into the turns. I can't think of another seven passenger vehicle that would have been as good along that stretch of road. Caddy Escalade? Nope. Honda Odyssey? Forget it.

Minivans bore me to death and most full-size SUVs corner like a drunken water buffalo. So if you really have to carry more peeps than you can fit in a luxury sedan, and still want to enjoy the drive, there's probably no better way to roll than a GL550. On dubs.