Originally Posted by dubbelop
The builders of our other tandem clamp all their bikes at the front seatpost. And why not, if the seatpost is inserted well into the seat tube it can't do too much harm (as long as you don't twist & rock the bike too much in the workstand). Or can it ...... ?
Not surprising; back in '94 you could run a Cannondale tandem over with a car and they wouldn't dent. Seriously, clamping any bicycle by frame tubes is -- IMHO -- the least desireable approach I know of and, at a minimum, the clamp and/or surface to be clamped needs to be protected with a cloth or plastic wrap to prevent maring of the frame's finish or any decals. Adding bulk to the area to be clamped and noting that most tandems use oversized tubing further increases the risk of crimping a tube with a pre-tensioned clamp used primarily on 1/2 bikes.
Back to captain's vs stoker's seat post...
Yes, it is possible to clamp at the front seatpost; however:
1. it requires you to lift the entire tandem to place it in the clamp (30 - 40lbs on average)
2. because of the stoker stem, it usually requires the captain's seatpost to be raised -- sometimes quite a bit -- which can be further complicated if the stoker's bars are fitted with a wired-in computer
3. it tends to be very unstable unless you remove the wheels and, frankly, there's not much you can do without the rear wheel with regard to drive train adjustments
4. removing either of the wheels completely upsets the center of gravity
5. given all of the foregoing, any wrenching on the bike usually causes the whole thing to twist back and forth in the clamp
Clamping at the stoker's seatpost:
1. requires only the rear of the tandem be lifted as the front wheel stays on the ground
2. more than 1/2 of stoker's seatposts don't need to be raised to fit the clamp and if they do it's not complicated by computer wires or stoker stems, etc..
3. tandems tend to be very stable when clamped by the stoker's seatpost since the tandem is also resting on the front wheel
4. removing the rear wheel is a snap and the front wheel can be raised off the ground using a 5 gal bucket or homemade brace for front end work
5. with the exception of removing the fork or headset, a tandem clamped by the stoker's seatpost is incredibly stable
All of that said, I will clamp tandems at the captain's seatpost for initial assembly of a new tandem where the headset and/or fork have not yet been installed. However, once the headset is in, the stoker's seatpost goes on and then the front wheel is installed so that the tandem can be taken down and then reclamped at the stoker's seatpost for all of the reasons previously stated.