As we know, the climbs in the HotW are tougher than the climbs in the ronde.
Also, there isn't any flat. Whereas in the ronde there is 90+km before you get to the start of the climbs.
But even the pros use slightly lower gearing - Sagan had 39x26 this year.
http://roadcyclinguk.com/gear/tour-of-f ... cPL3GYE.97
But the had other tricks to make it easier.
36x24 on 23mm is the reference for hotw. And it's not easy to do it on that. . Most people were on lower gears and wider tyres than that