Can any tell me the difference between these rim sizes as far as driving dynamics?
20" definitely look better, but with less rubber between the rim and road, do you feel the bumps more.
Also would you revommend the 19"'s for winter tires?

 

I drive 20's on the street and drive 19's on the track and 19's for the winter. If you are planning on participating in any track events, 19's are the way to go. They respond much better in the corners than 20's due to more flex in the 19 sidewall.

I drive 19's to the track (Michelin Sport Cup 2) and they are a slightly less bumpy than the P Zero 20's. The P Sotozero in the 19 version are even less bumpy.

Truthfully, if the ride is that important you can compensate with tire pressure. I use different pressures to alter the ride to the tire depending on how I am feeling about being bounced around that week.

 

I am surprised you feel 19" wheels are quicker in the corners

 

I think most people that are track experienced would agree with my comment. I have driven both 20 and 19 on the track. The 20's give very little feed back as they don't have the flex in the sidewall that the 19's do. The 20's just break loose whereas the 19's give you the "feel". When I first started road racing, I could not find one experienced reviewer that placed 20's over 19's. This is why most, if not all track tires are max sized at 19.

Hey, if you prefer 20's, that's okay too.

 

+1, smaller wheels and more tire make for more a more pleasant track experience. What blows my mind is that the GT3 RS (the definition of a track car) comes with 20 inch fronts and 21 inch rears.

 

didnt think we were talking about comfort

 

Who said anything about comfort?

 

Re using 19's or 18's for the track, is the thinking to actually select a tire to equal the same diameter as OEM?

I thought part of the reason to use smaller tires/wheels was to reduce costs and weight for consumables.
And that when using a smaller wheel, one would stick to using a similarly proportion wall height?