If you look closely at the photos, you will see that both mechanics are putting the connector pin through the leading end of the outer link they are connecting. In other words, when the connected outer link comes over the top of a cog and is simultaneously engaging two cogs during a shift, the connector pin will be the first one to move across the gap. The stress is higher on the rear pin of the link, as it is being released from the previous cog, so this choice ensures that the stronger, factory-installed pin is in that position. When connecting the chain at the bottom as in the photos, to make sure the connector pin leads over the cog, the connector pin needs to be on the end of the outer link closer to the rear derailleur.
Now comes the critical step. This is a section from the chain chapter of the revised edition of Zinn and the Art of Road Bike Maintenance that I am working on now: Rather than having both ends of the connecting pins protruding a bit from their plates (as they are for 7-, 8- and 9-speed chains), you want the 10-speed connector pin slightly recessed, beyond flush. The key is to go by feel rather than sight, and to keep pressing where you would normally stop with a 9-speed chain, because it feels hard. It will then feel easy, then very hard while continuing to push. At this point, stop to check for binding. You will know that you are done when there is no binding at the connector pin link, without flexing it sideways to free it up. Back off on the chain tool screw, check the link for freedom of movement, and re-tighten the tool if you feel any binding. If the link is still binding, Shimano says that there is a 99-percent chance that the pin isn't pushed in far enough to be fully seated.
Most mechanics free up a tight link by flexing it back and forth laterally by hand, and this is a hard habit to break, especially if you have been doing it for decades.
Shimano's Wayne Stetina says, "Never, never never (flex the link sideways to free it) especially 10-speed, but also for 9-speed chains. We need to get people away from this lazy bad habit when installing Shimano chains. If a Shimano chain does not move freely, the pin is not correctly seated in the back plate. If it is correctly seated, it WILL automatically be correctly centered. Loosening it like this may cause the connector pin to pull out of the plate. It will definitely cause a 10-speed chain to fail."
http://www.velonews.com/tour2005/tech/articles/8534.0.html
Now comes the critical step. This is a section from the chain chapter of the revised edition of Zinn and the Art of Road Bike Maintenance that I am working on now: Rather than having both ends of the connecting pins protruding a bit from their plates (as they are for 7-, 8- and 9-speed chains), you want the 10-speed connector pin slightly recessed, beyond flush. The key is to go by feel rather than sight, and to keep pressing where you would normally stop with a 9-speed chain, because it feels hard. It will then feel easy, then very hard while continuing to push. At this point, stop to check for binding. You will know that you are done when there is no binding at the connector pin link, without flexing it sideways to free it up. Back off on the chain tool screw, check the link for freedom of movement, and re-tighten the tool if you feel any binding. If the link is still binding, Shimano says that there is a 99-percent chance that the pin isn't pushed in far enough to be fully seated.
Most mechanics free up a tight link by flexing it back and forth laterally by hand, and this is a hard habit to break, especially if you have been doing it for decades.
Shimano's Wayne Stetina says, "Never, never never (flex the link sideways to free it) especially 10-speed, but also for 9-speed chains. We need to get people away from this lazy bad habit when installing Shimano chains. If a Shimano chain does not move freely, the pin is not correctly seated in the back plate. If it is correctly seated, it WILL automatically be correctly centered. Loosening it like this may cause the connector pin to pull out of the plate. It will definitely cause a 10-speed chain to fail."
http://www.velonews.com/tour2005/tech/articles/8534.0.html
