That's 700C to 650B for all y'all. I recently bought a used Salsa La Cruz specifically with this project in mind. With disc brakes and a high-ish (68mm drop) bottom bracket, it looks like the perfect bike to do a quick and easy conversion on. Inspired by this, http://www.bikeman.com/bikeman-blogs/650blog/1888-salsa-la-cruz-650b-conversion I knew I was good to go.
I found a used Velocity Blunt wheelset on Craigslist, and was able to get a pair of Vee Rubber Speedsters (I know, hard to make out the name on them) from my friend Mike. So far the entire investment is under $1000 which is where I wanted to be in this experiment.
You can see the comparison between the two wheelsets below. The 700C is about 10mm taller at the top. Five mm at the axle. Imperceptible ride height difference.
But what a difference in ride quality! Riding off-road with the 700X31C stock tires was miserable on this bike. I don't know if it was the tire or an extremely rigid fork, but my hands and arms would ache after riding. Really disappointed about that. I might play around with some different 700C tires and see if it can be improved. Probably some SOMA C Lines in the future.
The Vee Rubber Speedsters measure 47mm, and are slower on the road, but excel in the dirt. Especially on hardpack fire road type riding that I do a lot of here in Inland Southern California. They're not so great on singletrack, but everything in life is a compromise! The hand pain I mentioned above is eliminated. The bike just flies over irregularities in the trail now.
There is a weight penalty with the 650B wheels though. About 225grams/8oz. per wheel. That's with disc and skewers installed. The 700C does have a lighter disc. Hubs are both XT M756, 32 butted spokes, Velocity Blunt 650B and Salsa Delgado 29er rims.
I'm going to raise the bars and bring them closer, as a stretched out road position doesn't work so well in the dirt. Other than that and maybe eventually putting some knobbier tires on, this bike is a dream to ride in the dirt!
One final look:
