The Truth experiment using a 650B front wheel (that's a 27.5-inch tire) is revealing much better results than I ever expected...actually I was not sure how it would ride or handle even though I spent an abundant amount of time designing this thing (I knew a total flop was possible and just part of the risk that goes with bike experimentation).
I put a lot of miles on the Truth as a 26"-wheeled only bike so I already had a feel for it's handling and biases in different situations. Since putting the 650B wheel up front I have put a the bike through a few "gentle" thrash tests...the ride results thus far are truly amazing in comparison the the 26" only wheels. Just to be sure I was not on some euphoric new-bike high I swapped the front wheel back to the 26" a few times and found that the 650B wheel up front was the only way to go in everything I rode through.
My test have mostly been at Hells Gate State Park - a place I am beyond familiar with that has a huge variety of trail conditions and geograghy...i.e. twisty-fast single-track, an uphill with some obstacle laden switchbacks, a steep downhill that is always full of rocks and sometimes slick muddy patches, short-fast rollers (some with 90-degree corners and off-camber turns), big-ass endo rocks, ruts galore, deep sand patches, billions of horse-hoof divets, small (but deadly) rock gardens, weeds, and sometimes snow. So far the 650B front wheel has me smiling big on everything...
Soaking up trail-noise: The 650B-wheel really made a difference in soaking up the smaller trail noise similar to what I have found riding 29ers. Trail noise in this riding area are horse-hoof divits, which have a tendency to rattle your teeth a bit even with the finest forks. But the larger front wheel really shined in this stuff. I rear suspension of the Truth works so well that I never really notice the bumps transmitting from the rear wheel...hmmm once again dare I say it works as Ellsworth advertises.
Endo testing: The 650B-wheel also proved to be much more endo proof - I actually tried to endo in my favorite deep V-shaped rut and couldn't make the bike do it with the 650B-wheel, but with the 26" wheel on front it wanted to endo every time.
Cornering - WOW is all I can say...I was appoaching these well-known-to-me turns just as I have thousands of times before (i.e. brake just before the apex then let up and rail though), but I started noticing I could take the corners faster and faster until I was not braking at all - a scary-thrill to say the least. Again, just to be sure I was not on some sort of super-human high I rode the Truth with 26" wheels and one of my 29ers through the same stuff and could not come anywhere near to speed in the same corners, then I did it again on the 650B Truth and was again railing through at unchecked high speeds. A large part of this ability I would say comes from the tires - the Pacenti Neo-Moto grips remarkably well, yet it is a nice large volume, fast rolling tire...a rare combination.
Rocks, ruts, and sand: The 650B rolls over the worst of it with ease...let's just say that there is a huge difference between the 26" only Truth and the 650B Truth and say enuf said.
I even took it out at night and rode the entire place (including the Devil's Slide) after it snowed - again I must say that the Pacenti Neo-Moto 650B tire is beyond impressive for traction...I did not slide out or ever loose control on the worst of it, I popped in/out of ruts with ease, and basically rode to the limits of my lights (which was stooopidly fast since I was doing this alone). The only problem I encountered was a face-to-face near death collision with a set of terrified running antlers attached to a wild-eyed deer (I'll bet I was a little wild-eyed at about the same time plus I was screaming as I was braking hard).
I'm still planning more "tests" (rides in disguise)...