Do NOT try to adjust the collars on the 1981 and later pushrod tubes...they are brazed in place. It is unclear to me exactly when the brazing first began; I believe it was phased-in during the 1981 production year. I HAVE seen earlier brazed ones! Some literature will state that it was from the 1981 change to Nikasil cylinders. If you have earlier adjustable ones, you could back them off a bit before assembling the cylinders to the block, and adjust them after you are all done. Frankly, I feel these should not be touched at all unless grossly wrong; and setting them too tight to the seals is hard on the seals, particularly the /5 types. The WORST thing you can do would be to bang on them and damage; or, WORSE, move the tubes. If you insist, there is a BMW tool ....HOWEVER, a very simple tool from a piece of old electrical conduit can be used to work on the collars. See any Clymer's or Haynes for the sketch....but, again, I feel you should leave the movable version of the collars alone, unless grossly at the wrong depth. The collar ring is about 5 mm below the cylinder base seating plane surface at the highest point. One thing you sure want to do is avoid ever having to replace a pushrod tube, as the process and special tool needed is unpleasant, and you surely will ruin some new tubes in the learning process. Aftermarket stainless steel ones are the way to go. You need a well-fitting mandrel. Seibenrock makes one, I think.....and there is also the front axle! More information later in this article, because some of you WILL someday replace tubes. Perhaps yours are rusting or leaking.