I belive i actually read specificaly last night you are limited to changing your wheel no more then 1" of its org diameter, or it can bump you up a class. how ever i've only read some 24% of the pdf, and only once, i could easily be wrong, other then there is some specific mentions in the rules about wheel changes
smaller diameter means you can rotate it quicker (less hand over hands for 1 rotation) , if you were to loose power steering a smaller wheel should make it harder to turn.
and turning your wheel 60 degrees is still 60 degrees cody.

unless your change your steering ratio