Hello just got a c250 2.1 sport and it has to Toledo 255 / 35 zr18 95w tires on it , it's ok on the motorway but at 50mph it makes a droning sound , will it be the tires hope it's not the diff.
Have you not downloaded the mercedes guides? That should have your car and all the info you need.
I have it on my phone as an app
It's been a very useful tool, helped me out loads of times
His - Denim Blue A220 AMG Line Premium / Hers - Obsidian Black R172 SLK55
Most likely the tyres. If it's the diff, then going between neutral throttle, slight overrun and slight acceleration will change the volume of the drone. Bet it doesn't...