On 7/15/2018 1:00 PM, wrote:
I have a friend who just bought a new 29"-wheel Motobecane MTB and swears that, due to the larger-diameter wheels, it "pedals easier" than his old 26"-wheel MTB did.

Have you ever heard anyone say this before? I have.

Since the contention does not seem correct to me, I was just curious about how you gentlemen would respond to it?

I might point someone to the book _Bicycling Science_ by Wilson.

All things being equal, on typical road surfaces, a larger diameter
wheel should roll easier. But for slight differences in diameter, I'd
expect the differences in rolling resistance to be slight.

I'd expect tire choice to have a greater effect. That includes tire
width, as well as tire construction. Choice of pressure will also be
significant, and higher pressures do not always mean lower rolling
resistance on real roads.

Then there are the psychological effects to deal with. If he believes it
rolls easier, his 29er may indeed post faster times. Ditto if he paints
the bike red, if it has European cachet, if he replaces his steel water
bottle screws with titanium ones, if he buys more aerodynamic
sunglasses, etc.


--
- Frank Krygowski