Originally Posted by
miniapple3
The Co-Motion Periscope has a wide range of adjustable in the stoker position. The dual telescoping seatposts gives a lot range to adjust. There are to frame sizes for the front.
I thought the main advantage of the periscope was to allow particularly small stokers as well as normal-sized ones - that wouldn't seem to help in the current situation.
My wife and I are very similar sizes, I'm maybe 1" taller, we're both around 5'8". We both have rather short legs and longer torsos, this doesn't cause many problems in getting single bikes to fit well, but it has turned out to complicate things with our tandem a little.
We've found that the stock length of the stoker's compartment on our Co-motion Speedster is actually a little on the short side, to get the same reach as on our single bikes, we use a stoker's stem of just 110mm, plus the stoker's seatpost is a ThudBuster, which has a decent amount of setback. This puts the stoker's bars right under the captain's seat; we might put the stoker's bars 1cm higher if we could, but that just isn't possible, but we're OK with that because they are JUST high enough where they are.
I'd therefore recommend not only thinking about seat tube lengths when choosing a frame, but also top tube lengths. I did this when we bought our frame, and the captain's top tube length is what I would have on a single bike, but now that I have to use a zero setback seatpost to keep out of the stoker's way, I have to use a 2cm longer stem than I would normally so that I maintain the same reach. It was hard to consider what length of stoker top tube would be needed before we bought it and had got used to the bike, because the stated length of a stoker's top tube is not really comparable to the equivalent dimension on a single bike. I made the assumption that since even the largest stock Co-motion frames have the same length stoker's top tube, then this size cannot be particularly short.
If we were to get another frame, we would get it custom made with the same seat tube lengths, but 2cm more on the stoker's top tube, and 1 or 2cm more on the captain's top tube. However, we'd then probably not be able to use the Gate's carbon belt drive that we have on this bike, the frame might flex a tiny bit more, and it would be harder to pack in the S&S travel cases, so there are some advantages of what we ended up with, and I'm not entirely certain that I'd want to give up these advantages since we have now been able to get it to fit almost perfectly.