175 question about gearing

I drive a 06 ultra with a sidecar and need a better option than the stock Dunlop. The stock tire is 140/80r16 and I know from reading the austone will fit and I might order one. My question is I have a built 107 motor and need the revs up and was considering gearing down the front pulley to raise my rpm. I am assuming the 175/60r16 might have the same effect and solve my tire life problem. Seems that it is lower and I do not know the overall Impact. I saw a guy installed one and hated it but for a hack it might be ok.

Any thoughts

Here is a link to a tire size calculator http://www.discounttiredirect.com/direct/infoTireMath.do
It is also posted in a sticky in the Tech forum.
Plug in your tire sizes in to get the revs per mile then it is simple math
to figure your sprocket ratio to give you the engine rpm, at mph, that you are looking for.