Do smaller rim sizes make for a smoother ride usually? Assuming they have all-season tires and not performance tires.

 

Maintaining the circumference of the stock tires is important to maintain the accuracy of your speedometer as well as optimizing the stock gearing. However, if you find the ride quality too harsh as many do, you can install smaller diameter rims with higher profile tires (maintaining stock circumference) to reduce the harshness a bit but that comes hand in hand with a reduction in the handling precision. You will only achieve so much as the shocks and springs are tuned for a sporty ride but I did find the rid eof the 16 inch rims better that the 17 inch S rims and Waayyy better than my 19 inch Konigs which were just silly.

I hope this helps.

 

yes

 

Not to state the obvious but, I will. If you currently have run-flat tires, chuck-'em!! They destroy ride quality.

 

Yes a smaller rim with the recommended tire size to match on the car will increase ride quality because there is more tire to absorb the impacts. Also, usually a smaller rim is lighter and lends to less unsprung weight which allows the suspension to be more effective. But as mentioned above RFT's will adversely affect ride quality no matter what because the design of the tire has a stiffer sidewall to maintain rigidity when there is no air in the tire, this in turn reduces the shock absorbing effect you would get from a conventional tire.

 

You need to understand which brakes are on your car, they will limit how small you can go. A base cooper will handle 15" wheels, a S requires a 16" wheel, and factory JCW cars require a 17" wheel.

On my S, I had 16" runflat snows and 17" non-runflat all seasons. The ride quality was similar between the two, just for a comparison.

I agree with the above comments, runflat tires are harsher than non-runflats, and generally smaller wheels will give a more compliant ride.

Have fun,
Mike