Someone else may answer your rolling resistance question but another
consideration is snow traction.  Wider tires aren't as good in snow.    I
know this from 25 winters in Wyoming with various vehicles and tire combos.
Newcomers to Wyoming winters would show up with big fat showy tire combos on
their vehicles and soon learn this..or start complaining to the highway
department that "driving on their road was hard, and there was too much
snow. " A taller narrower tire configuration works better in snow.
  Don Hanson

On Tue, Sep 8, 2009 at 10:26 PM, Jeff Palmer <jpalmer@mts.net> wrote:

> Hi all,
>
> It's getting to be time to replace the 14 inch tires on my 85
> Westfalia.  So I'm thinking about an upgrade to 15 inch wheels.  I
> know on my hybrid bicycle the tires are much narrower than on my
> mountain bike, and the rolling resistance is much lower (empirical
> testing from an arts student!).  So I'm wondering how moving to larger/
> wider wheels and tires would affect my fuel economy.
>
> Thanks in advance
> Jeff in Winnipeg (hey summer just arrived!)
>