While awaiting a replacement part for the hub on my commuter, I'm riding my fun bike to work. It's got 27 x 1 rims with 27 x 1-1/8 tires, rated to 90 psi. And I got to thinking... reportedly, fatter tires have less rolling resistance, but will I really notice the difference? A couple of possibilities:

1. I don't know if I can put even fatter tires on 27 x 1 rims. There must be a point where the tire is in danger of rolling off the rim, going around turns. Or, some other evil that I don't know about.

2. I could give myself a winter fun project and string up some wider 700c rims. I've got enough clearance in the brakes to accommodate what I think is a 4 mm reduction of rim radius.

Any thoughts?