Originally Posted by
marciero
... one reason I got the bike was that the disc brakes and clearances allowed the option for 650b, which is the way to go if you want to do a lot of gravel riding. A 42mm 650b will have almost the same diameter as a 25 in 700c
We have one tandem with 700c wheels with 28 mm tire (maximum size that clears the frame and fork). Our other tandem has 650b wheels with 42 mm tires. The wide tires are really nice on rough roads and paths. We have plenty of room on that bike to install 700c wheels. I am not sure there is much difference in speed. If we ever downsize to a single tandem, the less versatile one is going to go.