I'm surprised to hear this. I don't mean this to sound rude but did you test drive the car first? The ride on the RCZ with 19ins alloys is...erm..."firm"...there can be no denying of that but then you're comparing it to your Merc which is built for comfort (unless you have an AMG version). The Ka probably is a softer ride. My wife's Fiat 500 is too but I certainly wouldn't say that it "drives much better". It's just more comfortable on our pot hole filled roads. You have to bear in mind the tyre profile and the size of alloy. Both of these are going to provide a firm ride with fair amounts of road noise. Be interested to learn what you decide but sorry to hear you feel this way. can fully understand what you are saying, and yes i did test drive it but the roads i drove on were quite smooth, the roads where i live are not quite as smooth, i didnt expect the same ride as the merc, even though the clk was a cab, and 5 years old, it didnt rattle and vibrate like this car does,just being honest thats all, maybe it will grow on me, but at the moment i feel gutted,think i should of stuck to german cars,before the merc i had a 525d and before that i had a audi a4 cab, i dont know perhaps ive been spoilt.