Performance and "rolling" weight

First off, I am no expert here - so if anyone has better information to add (correct mine) please do.

I was thinking of upgrading my wheels to 20", but got to thinking about the performance impact. As I thought more on it, I think there is room for improvement - but I am not certain it lies in the 20" rim arena. Here are the known factors that weigh heavy on my (or yours also) decission...


[1] Unsprung Weight - This is one of the most critical factors affecting a vehicle's road holding ability. Unsprung weight is that portion of a vehicle that is not supported by the suspension (i.e. wheels, tires and brakes) and therefore most susceptible to road shock and cornering forces. By reducing unsprung weight you, in effect, provide more precise steering input and improved turning characteristics.

[2] Reduced rotation force - Improved acceleration and braking are the major benefits from a reduction in wheel and tire weight. Given 2 wheels of identical circumferences and coefficient of friction - the lighter wheel will provide better overall performance. Reducing the wheel mass, also reduces the gyroscopic effect of the wheel. When a wheel is spinning, it is very difficult to make it change direction, but the lower the mass of the wheel, the easier it is to steer.

The best argument I can think of in favor of a 20" setup is that by reducing the sidewall height, this would reduce the "squishy" feel and provide a stiffer and more stable turn.

I would hink that the 18's are likely the best bet (as I think that I can get the lightest setup this way), but am interested in seeing if there is a good argument in favor of the 20's (I'm deadset against the 22"). If there was a 20" setup that didn't significant penalize a similar 18" setup (or other unconsidered performance benefit) then I'd like to know now before I begin looking to get baby some new shoes!