A few years ago, Mark here put some 700C disc wheels on his Surly Troll, which is a bike designed around 26" mountain bike wheels. Mention this on any bike forum, and you'll be met with "experts" who insist that changing wheel sizes will make handling too weird. But in reality, a 700x32 and a 26x2.4 have similar overall diameter, so handling is affected minimally. Since then, we've converted at least two 26" Disc Truckers to 650B and even 700C. Yes, things change about a bike when you change wheel sizes, but that's why we do it. Like all bike choices, there are trade-offs to swapping wheels. There are circumstances where one wheel size is just what you need, and the other would be less optimal. Then there are other circumstances where the reverse is true. Luckily, these decisions aren't permanent.
I have two wheel sets for my Ice Cream Truck. Here it is with a typical fat wheelset, Clown Shoe rims and Bud tires:
|These fat tires are just the ticket for riding into an uncertain future.|
And here is the same bike with 29+ wheels, Stan's NoTubes Hugo rims and 29x3" Knard tires:
|It doesn't even look weird.|
Here's another example - two Surly ECRs, one with the usual 29x3 tires on Rabbit Hole rims:
And the other with normal width 29"/700C rims and the amazing Compass 700x38 tires.
Again, the internet experts will insist that this is a bad idea. But listen to this: The wheelbase and bottom bracket drop on the ECR is nearly identical to that of a similar sized 700C Disc Trucker. Nobody would suggest that 700x38 isn't appropriate for a Disc Trucker. Not surprisingly, the handling of the skinny-tire ECR is reminiscent to that of a Disc Trucker, and it has all the braze-ons for rack touring... So here again, we have one bike with two wheelsets serving a wide variety of needs.