Originally Posted by
Grand Bois
What washer? There's no washer. Be careful about using a wrench on the pivot bolt. That's the end of it you see in the picture above. If you apply too much torque, it will spin in the plate with the tab and you'll have no spring tension. It doesn't take much. I learned that the hard way. There's really no need to use a wrench at all. Just tighten the bolt from the backside. The pivot bolt won't turn because the tab stops it.
The pivot bolt is actually a nut in this application because the threads are female.
You are correct, that is not a washer. Pardon me for using incorrect terminology. I have corrected the original post. However in this case, as the plate is not installed on the pivot bolt, the OP will need to use an allen wrench in order to pretension the spring to install the plate on the pivot bolt in the correct position. To further clarify for the OP, note there are flats on the pivot bolt and in the mounting hole of the plate so that it won't just spin. You may have to tap or press the plate onto the pivot bolt. Once that is done, it can be mounted, making sure the tab is on the front side of the hanger, and the retaining bolt can be installed. If done correctly the derailleur will swing toward the back of the bike. The picture I shared earlier shows the correct orientation of the plate.