Tyres are Continental rear 255 x 35 x18, fronts 235 x 40 x18 and mileage is 24k.
They are the same size tyres that are on My 2018 SLC43, with ContiSportContact Tyres - Do You have the AMG 10 spoke as per picture below or the optional multi-spoke design? (Not that it should make any differenc)
Another strange thing the car does is not move when put into gear or at least not until you gently stab the throttle. My wife almost crashed into the driveway gate yesterday. I manage to get around it by keeping my left foot on the brake and giving it a bit of gentle throttle until it breaks loose. Is this normal? Seems like it might be a function of the electric handbrake..
Coming from a manual V6 engine with a nice hydraulic clutch, I find all auto's difficult to manoeuvre at very slow speed, especially over the garage door lip (well I did till I took the grinding disk to it..!!) Using left foot braking at low speed is a good skill to have.
With the new SLC 9 speed auto box, all I do is select "D" and press the accelerator to go - No need to release the electric parking brake..!! I do find the new 9G box in the SLC different in operation to the 7G box in My old R171/350 SLK - Has taken a time to get use to how it works to get the most out of it.
Going back to Your original comment about asking a dealer about the ride, as there are less than 500 x SLC 43's in the UK, it's difficult for them to be an expert on them...
If You ever make it over to the M3 or M4 - West side of London, I'd be more than happy to meet up to see how the two SLC43's compare.. If there was a difference/problem, You could then go back to the dealer, especially if any of the 3 years warranty is left?