Today's weird idea was sparked by Cannondale's newish Slate series... basically, a road bike with 650B (gag, 27.5") wheels, fat tires, and Cannondale's mono-legged Lefty front suspension. Yep, it's one of those super-trendy (gag, again) "gravel" bikes. If you have $3k just burning through your pocket, you can get this one with Shimano 105 (that's the budget model).
The concept, I'm on board with -- make a road bike that's ready to handle anything (though I find it hilarious that the Cannondale marketing team has decided to call this category "New Road" -- um, why does one need fat tires and suspension on a "new" road?) But I'm no fan of disc brakes, and I've always found the Lefty fork weird and off-putting (even though - brag mode on - I worked in one of the first bike shops to ever see a Lefty in the wild, since we were just down the road from Bedford). In this case, it's a Lefty crunched down to only 30mm of travel, which seems like a lot of fork for not a lot of function. So I got to wondering, didn't Cannondale do "suspension road" before? And couldn't that platform be turned into a capable all-surfaces bike?
Answer to question 1: They did. Exhibit A, the 1999 Silk Road 500...
(Image horked from bikepedia.com.)
Of course, that's no all-surfaces bike. The tires are 700x23, and the bars are so freakin' low, it makes my back hurt just looking at them. But the bones are there... light, wide gear range, and a 25mm-travel suspension fork to take the edge off, without the weirdness of the Lefty.
So how do you answer question 2? Through the magic of those 650B (argh, gag, 27.5") wheels. A 650B wheel has a diameter of 584mm, while the 700c wheels on the Silk Road are 622mm. Math is hard for English majors, but even I can figure out that 622-584=38 (the difference in diameter between the two wheel sizes) and 38/2=19 (the difference in radius between the two wheel sizes). A smaller radius is going to need more brake reach, so if you can find a brake that will reach an extra 19mm, you can put the smaller 650B wheels on the Silk Road and create a ton of tire clearance. Being a race bike, the stock brakes are 39-49mm reach (positioned with the pads around mid-slot, likely 54mm or so), so you could plug-and-play the Tektro R556 brake (with its 55-73mm reach) and probably get there just fine.
Are you seeing it now? Race bike, chubby tires, some suspension. It just needs that slammed stem flipped over, and voila. Cannondale invented the gravel bike in the late 90s and didn't even know it.
(Credit where credit is due: I didn't come up with this idea on my own. iBOB list member Ed Braley was an early proponent of using 650B wheels to make otherwise useless road race bikes into something more fun, and you can see examples of this conversion in real life on bikeman.com's 650Blog. But I've never heard it attempted on a Silk Road, in theory or in practice.)