alternate tire sizes
Somebody here may know if there is enough clearance to run 255 or 265's, but also do check as to how much speedometer error the increased diameter will cause. You will be going faster than your speedo indicates, thus inducing risk of speeding citations. There may also be some degradation of performance (slower acceleration) due to the taller tires.
Most of the folks who are trying to improve the ride of the E-Class cars with Sport suspension seem to focus on switching to 17-inch rims with the stock 17-inch tire sizes. These ride softer due to their taller sidewalls, but they don't look as "cool" and don't corner as well. The advantage, though, is that these are stock MB parts, and speedometer accuracy can be maintained.
On my previous cars (Lexus LS's), I chose to upgrade from factory 16-inch wheels to factory 17-inch wheels. I then bough wider aspect ratio tires that had the same outside diameter as the stock tires. That way, I got more tread width with no loss of speedometer accuracy and little impact on acceleration. Tires just looked "super wide" from front or back, looked stock from the side. That met my "needs" -- but your intent could be entirely different.
BTW - Unless your dealer service department is unique, don't expect them to offer any help. They will only advise to stay with all stock, or with other size choices that were offered as stock on other models of W213. They usually are not allowed to recommend any "custom" options. Maybe a tire shop (TireRack?) has enough data to know what fits. Call them - they have been very helpful to me in the past.




