Hello,

I have to exchange the front bottom bracket. ( captains side )
Are there some tips for fixing the new bb with the resault, that both cranks ( captains + stokers )
are in the same position ?

You should not have a problem re-timing the cranks after installing the new bottom bracket. When you re-install the timing side crank, put on the chain while the stoker's crank is strait down, pull the chain tight with the captain's crank strait down, rotate the BB to match the splines or tapers, slide on the crank. Before tightening the crank bolt, check that both arms are in time. If not, take off the crank and move the chain as necessary on the captain's timing gear to time the cranks and re-install.

Edit: Here is a trick you could try if you are only replacing the bottom bracket, not the timing chain or rings:

Rotate the cranks so the timing side cranks are pointed forward and level. Take some twisty ties and tie the chain to both timing rings in several places to hold the chain on the rings - 2 or 3 ties per ring. When you go to re-install the captain's timing crankarm, just pull the chain tight by the pedal, level with the ground and rotate the bottom bracket to meet the splines or tapers and slide it on. Since the chain did not move off the rings, the bike will be in time as before.

Assuming they are aligned they way you want them to begin with (aka, in-phase or in a desired out-of-phase position), you can put alignment marks on the chain and chain rings which will ensure the chain goes back on each crank in the exact position it came off. Use a little spot of touch-up paint or an indelible marker to put marks next to each other on both the front & back chainrings and chains, i.e., with both crank arms hanging down in the 6 o'clock position, put marks on the chain/chainring at the 5 or 1 o'clock position on the rear (stoker's) cranks and at the 7 or 11 o'clock position on the captains. Note: if you go 3 & 9 o'clock back and front you've got a 50/50 chance of getting the chain reversed. If you put the marks on a clean chain & chain rings they'll usually stay there a pretty long time if you don't remove them with solvent.

Other than using alignment marks, just use the seatposts as alignment references. If both crank arms fall in line with the seatposts then they will usually be in-phase.

Note: If you have a situation where both cranks can't be perfectly aligned it's usually best to have the captain's crank "leading", that is slightly ahead of the stokers.

Final comment: If the timing chain has been on the bike for a while it really is a good idea to use alignment marks or some other method (such as described by Galen) to make sure the chain goes back on in the same position that it came off. Timing chains tend to become "matched" to their timing rings if left on too long (e.g., beyond normal chain wear replacement guidelines of 1/8").

Rather than blathering on about it, if you haven't visited Sheldon Brown's "sync chain page" before let me suggest that you give it a read: http://sheldonbrown.com/synchain.html. This particular issue is addressed near the bottom of the page.

Normal chain wear replacement guideline of 1/8" wear per foot of originally 1/2" pitch chain.

Twenty miles today on the single. 96 more days and I am a cyclist again....might get two tandems out tomorrow to victimize friend and her boyfriend (on one tandem) and her daughter (with me on the other one).

No I don't have flu or bronchitis or a sinus infection. Yes, I am riding. Yes, I am happy...