Tire Swap Gives Our Mercedes-Benz E450 Huge Performance Gains

We like the Mercedes-Benz E-Class a ton, but something has disappointed us with our yearlong 2021 E450 test car. How could a model providing such sublime ride quality in our initial testing deliver more average responses in subsequent test cars? Without switching to 18-inch wheels like the 2021 Car of the Year sedan, we decided to install a new set of tires for our yearlong E450 and see if we could improve the picture. And things did change, but not in the way we expected.

For a luxury sedan, our yearlong 2021 E450 test car simply emitted too much road noise into the cabin over imperfect surfaces. We found the car rides too rough, as well. It's a tough balance, meeting expectations for handling and acceleration while being simultaneously comfortable and luxurious. There's nothing egregious here; but it's not as good as a couple editors remember from the E450 sedan at 2021 Car of the Year testing. Our E450 should have everything it needs to be a great highway cruiser, with the available air suspension and the quiet Acoustic Comfort package.

Choose 19-inch wheels, though, and your experience may echo ours. On a recent road trip to Gilroy, California (just over 300 miles north of Los Angeles), Mexico editor Miguel Cortina found plenty to like but wanted more from the ride quality and highway noise levels.

"While wind noise is relatively controlled, tire noise is definitely louder," Cortina said.

So, thanks to our friends at Tire Rack, we replaced our Goodyear Eagle Sport all-season run-flat tires (245/40R19s) with a set of Bridgestone DriveGuards—an all-season run-flat tire optimized more for ride and longevity than sport.

To our surprise, the new Bridgestone tires made their biggest impact not on the street but on the track. Braking distance from 60 to 0 mph shrank from a subpar 135 feet to just 122 feet. That's a more class-competitive number for the midsize luxury sedan segment. Acceleration to 60 mph improved one tenth of a second to 4.5 seconds, but the beauty of this mild-hybrid I-6 engine has always been the way it feels on the street, not its surprisingly quick sprinting abilities.

Handling improved, too. The E450 cornered at 0.89 g (average) on the skidpad, up from 0.86 g before the tire swap. Thanks to the new tires, the Mercedes also upped its figure-eight performance. A MotorTrend signature test, the figure-eight evaluation tests braking, cornering, and acceleration, as well as the transitions in between. Pre-tire swap, the E450 finished the figure-eight course in 26.3 seconds at 0.68 g (average). With the updated rubber, those numbers improved to 25.7 seconds at 0.72 g (average).

Here's what road test editor Chris Walton had to say about the E450 on the figure-eight course: "It does appear these tires have better grip than the previous ones. They didn't fall off a cliff this time. Decent and predictable under braking, then it turns in nicely, and takes a very neutral balance. There's even a whiff of oversteer that the all-wheel drive sorts out nicely. … Overall, probably much sportier than most E450 drivers will need. A noticeable improvement in demeanor and results."

What didn't appreciably change, however, was comfort or noise suppression. Our E450 still feels about the same for ride quality and highway tire noise as before. That's unfortunate, but we're at least pleased with the performance results. Just like the E450's superb powertrain, the value of the added performance on a luxury sedan isn't in using it every day but in knowing it's there.

As of this writing, the Bridgestones for the E450 cost $273.99 per tire or just under $1,100 for a set of four. Although run-flat tires can ride harder than other tires, we were reminded of their value on the way back from testing. After hitting a nasty pothole and blowing out a tire, the MotorTrend staffer at the wheel was able to safely drive a couple additional miles to the office.

Having said that, a couple of us still wish our yearlong E450 test car's tire noise on the highway and ride were better. Our advice remains the same: If you're considering an E-Class in E450 form, pair the standard 18-inch wheels with the air suspension—otherwise, consider the more performance-oriented E53.