Anticipate that this study will add more fuel to the fire. 

Posted by Bike Radar:
After years of arguments and speculation as to which mountain bike wheel size is fastest, we tracked down someone who's trying to prove it... with actual science!

Test Protocol described in Part 1 (posted Jan 23, 2015):
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Results described in Part 2 (posted Jan 30, 2015):
The data is in, the maths have been done, and Dr. Howard Hurst is ready to declare a winner... sort of.

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this was a pretty cool video.

one thing i am curious about is that 29er may have been the best out of this study but is the wheel going to be stronger given the bigger diameter? its easier to compress a larger diameter than a smaller given they both have the exact same specs.

Strava tells me my 27.5 is fastest followed by 26 followed by 29

29 -> XC, 26 -> DH, 27.5 -> bike companies trying to sell new bikes after saturating the market...

For trail, a 29er is fine...I consider XC and trail the same thing.  But the wheel base on those slacker bikes makes the steering even more sluggish with 29" wheels.  While 29" do roll over smaller obstacles better when decending, the steering gets to be an issue when it gets real chunky.  This opinion was formed by owning/riding a 140mm 29er.   

Now, this is all one man's opinion, but all of our opinions are based in our experiences and observering the experiences of others.  So take that for what it's worth.

I honestly take experience based opinions in high regard. Thanks for the info it helps me know what to look out for. I may like what others did not. Or I might be like "oh this is what they were talking about" and not like it either. 

I'm always interested in others opinions.

Mr.B wrote on 02/06/15 at 7:15am:

You should ride the new Specialized Enduro 29er!  Word from one of my part timers who raced on the Specialized GROM is it manuals as well as the 26.