Anyone see this: http://www.cyclingnews.com/features/...f-wheel-energy ?

Wider tyres roll faster than narrower ones: Many riders have argued for years that narrower tyres – especially on the road – are faster and more efficient than wider ones when in fact, the opposite is true. According to Wheel Energy, the key to reducing rolling resistance is minimising the energy lost to casing deformation, not minimising how much tread is in contact with the ground.

All other factors being equal, wider casings exhibit less casing 'bulge' as a percentage of their cross-section and also have a shorter section of deflected sidewall. How big a difference are we talking about here? For an equivalent make and model of tyre, Wheel Energy claims the 25mm-wide size will measure five percent lower rolling resistance on average – the supposed average limit of human detection – than the more common 23mm-wide one.

Unless you're a pure climber and solely focused on weight, the takeaway message here is that you'll go generally faster on wider rubber even if it's slightly heavier.