yes, tires

Okay, first of all, I used my friend "search" and read all the threads on this well worn topic. My main question has to do with how much I can vary from the spec tire sizes, i.e., front tire is supposed to be 110/90 - 16 and I've seen on other threads that some have used 100/90 - 16 and others 120/80 - 16.

How about the rear tire, which should be 130/90 - 15? Can we use 140/90 - 15? Which is the key variable to consider, the width or the radius? By the way, I have a local shop who quoted me a price of $116 to install and balance both tires (on the bike). It's a good price for around here, but I wondered if others around the country think it sounds high, low, etc.?

Thanks again,

Keith