You might be better advised to drop an inch, or even two, for a set of rims for winter tyres. Honest. I'm not sure what availability is like for winter tyres to fit 20" rims, plus the fact that winter tyres need to be a bit higher profile to be effective as far as I'm aware.
Thanks Gromit - the RS has simply enormous 8 pot brake calipers (each containing 4 disk pads) so clearance would rapidly become an issue, I think Spike pointed out that the parts list show's 19" rims though I've never seen an RS on 19s, seeing another RS Q3 on the road is pretty unlikely.
To be fair though there is quite a good choice of winter tyres in 235/35 20 - it seems quite a few cars use this size and as an example I'm using Luxury saloon (Jaguar fitment) Pirelli PZeros summer tyres - quieter and more fuel efficient than the AO Audi versions.
Hi I have a set of genuine Audi q3 sq3 alloys for sale in excellent condition hardly used tyres are 225/50/18 Dunlop winter tyres bought new from Audi costing £2300 asking £1000 plus £70 p&p any questions call or txt 07891323430