We really like the Mercedes-Benz E-Class, but something let us down with our year-old 2021 E450 test car. How could a model that offered such sublime ride quality in our initial testing provide more average responses in subsequent test cars? Without upgrading to 18-inch wheels like the 2021 Car of the Year sedan, we decided to fit a new set of tires for our year-old E450 and see if we could improve the image. And things have changed, but not in the way we expected.

For a luxury sedan, our year-old 2021 E450 test car simply emitted too much road noise into the cabin on imperfect surfaces. We also found the car journeys too difficult. It’s a tough balance, meeting expectations for handling and acceleration while being both comfortable and luxurious. There’s nothing glaring here; but it’s not as good as a few editors remember the E450 sedan in the 2021 Car of the Year tests. Our E450 should have everything it needs to be a great tourer, with the available air suspension and the Quiet Acoustic Comfort Package.

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

“While wind noise is relatively controlled, tire noise is noticeably louder,” Cortina said.

So, thanks to our friends at Tire Rack, we replaced our Goodyear Eagle Sport all-season run-flat tires (245/40R19) with a set of Bridgestone DriveGuards, an all-season run-flat tire optimized more for handling and longevity. what a sport.

To our surprise, the new Bridgestone tires had their biggest impact not on the road but on the track. Braking distance from 60 to 0 mph decreased from a sub-par 135 feet to just 122 feet. That’s a more competitive number in the midsize luxury sedan category. Acceleration to 60 mph improved by a tenth of a second to 4.5 seconds, but the beauty of this mild hybrid I-6 engine has always been how it feels on the street, not its abilities to surprisingly fast sprints.

Handling has also improved. The E450 cornered at 0.89g (average) on the skid, compared to 0.86g before the tire swap. Thanks to the new tyres, the Mercedes also improved its performance by eight. A MotorTrend signature test, the Figure-of-Eight Rating tests braking, cornering and acceleration, as well as transitions in between. Before the tire swap, the E450 completed the course in eight in 26.3 seconds at 0.68 g (average). With the updated rubber, those numbers jumped to 25.7 seconds at 0.72g (average).

Here’s what road test editor Chris Walton had to say about the E450 on the figure-eight course: “These tires seem to have better grip than the previous ones. They didn’t fall off a cliff this time. Decent and predictable under braking, then it corners well and strikes a very neutral balance. There’s even a whiff of oversteer that the all-wheel drive sorts out nicely…. Overall, probably a lot sportier than most drivers E450 will need. Noticeable improvement in behavior and results.”

What hasn’t noticeably changed, however, is comfort or noise cancellation. Our E450 still feels about the same for ride quality and highway tire noise as before. It’s unfortunate, but we’re at least happy with the performance results. Much like the E450’s superb powertrain, the added performance value on a luxury sedan isn’t in using it every day, but in knowing it’s there.

As of this writing, Bridgestones for the E450 are $273.99 per tire or just under $1,100 for a set of four. Although flat tires can roll harder than other tires, we were reminded of their value when they returned from testing. After hitting a nasty pothole and flat tire, the MotorTrend employee at the wheel was able to safely drive a few more miles to the office.

That said, a few of us still wish our year-old E450 test car’s tires sounded better on the highway and in the ride. Our advice remains the same: if you’re considering an E-Class in E450 form, pair the standard 18-inch wheels with air suspension, otherwise consider the more performance-oriented E53.

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