Not quite happy in the saddle
Well, I am near the end of my options, so it is time to cast about for other ideas. I got into tandems last year at about this time. I meticulously (ok, not quite so meticulous as it turned out) built the captain's area to be as close as possible to my single bike, which I am totally comfortable on. This required lots of changes to stems, etc.
I have never been completely comfortable on the tandem. The primary point of annoyance is the right sit bone. It gets sore, and eventually the whole right leg starts to feel like it is not right. I have measured and tweaked over and over to get it identical to the "control" position on the single. [Seat height from BB axle, seat setback from BB axle, seat setback from handle bars, seat angle] After I really really got them as identical as possible, I am still having problems. So it has to be something else, right?
The first thing I changed this year was the seat angle. I found to my surprise that the single bike saddle was a little down in front, maybe 1 degree (using a bubble, so I don't have an exact value). Changing the tandem to this made a big difference; I was able to last longer before the problems started. This also concluded all my efforts to make the position identical. I am as close as I can get.
So I changed the saddle to be identical (Selle SLK). I had the gel version of the SLK on there before. This definitely helped a little. I now consider the Gel SLK to be a "bad" seat. But I still have the problem. It just takes 20 miles before it become noticeable, and 40 before I really start to think about it.
But I still have the problem. I have the Eastern Tandem Rally, and the The Flattest Century in the East this summer. I need to be able to do 60-100 miles in a day. I am worried that I will not last.
Remaining potential causes:
1. The crank length appears to be different on the two bikes. 170 on the single (which is what I have always had), and the FSA Gossamer ones on the tandem appear to be 172.5. This is definitely a closely related dimension to the issue.
2. The tandem sitting issue. I sit 99% of the time on a tandem. Because of stoker wrist issues, we rarely both stand while pedaling, and just me standing is a little wobbly, although doable. But it can't be done as much as on the single, where I stand a lot.
3. The angle I am making to the saddle. I feel as if I am more upright on the tandem, even though I have gone to great efforts to match the positions.
When I go from the tandem to the single back to back (which I often do, and now more eagerly do to try to isolate this issue), I notice that I feel slightly lower in the saddle and more flat in the back. Measurements do not bear this out, by the way. It is just a feeling.
Another point: when I ride 25 miles on the tandem, enough to get sore, and then switch to the single, I instantly feel better, the problem goes away, and I can ride 35+ without a hint of a problem. This seems to kick out #2 above.
There is something different about these bikes, and I can't put my finger on it. Any ideas? I would love to try 170mm cranks, but swapping captain's cranks on a tandem isn't a casual thing. And could that 2.5mm difference really cause all this pain?