[Plutus]

I would like to know your opinion about change my rims M 18 inch for the 19 M 871 or 20 inch M872. What do you think looks better? Will I lost much confort? and fuel economy? My car is a X1 30e, waiting for your comments, thank you.

[kenrok1]

Fuel economy should be negligible if any (the overall profile / number of rotations remain the same more or less); comfort is subjective but less rubber and more rim is going to be stiffer… and last looks are also very subjective.

[DaveMc]

My M35i came with the 20" M872 and 245/40x20 Pirelli P-zero tyres. For winter, I've bought a set of used M871 19" wheels and fitted Michelin 245/45x19 CrossClimate 2's. The overall diameter is the same (1mm)
It's obviously not an apples to apples comparison, as the Michelin's are allseason tyres and the Pirelli's are summer tyres with PNCS noise cancelling system
The Pirelli's on smooth tarmac are pretty quiet, impressively so to be honest, but for £300 a corner, they should be. Even though I like them and don't buy rubbish tyres, I doubt at that price point they won't be replaced. That said, for many years now, I have only ever fitted 'allseason' tyres to my cars.
So to try and give some light to your question. Is there a noticeable difference?
Noise - Slight increase in noise on Michelins, but certainly not loud or irritating in any way.
Ride comfort - Michelins slightly less harsh - yes I can tell the difference, but not night and day different. But, to be fair, the Michelin's tread is noticeably softer than the Pirelli's and will be more compliant too.
Economy - Too soon to say, but I expect there will be some penalty in economy, but that to me is a price worth paying for safer winter motoring.
Dynamics - To be honest, I don't really challenge my tyres, but on a 'spirited' acceleration burst yesterday, nothing bad to report. The 19's weigh about 3lbs less than the 20's at 56lbs each, so the smaller wheels 'should' improve dynamics to some degree, but subjective.