Roller and chain sort of centers itself to the tooth U being that sloppy for this purpose, so it is not alignment per say of the roller to tooth. Alignment is if my adjuster has one or more flats past than the other side. That more or less is cocking the axle some. This is called misalignment when the axle is cocked in the swing arm, not the roller and hoop so much being out of line.
Roller and hoop show wear riding up the hoop, at the sides of the hoop and that is thrusting the tooth wide upon, horizontal push, accel, and lift. Add those 3 wear points, this tends to make the U wider and elongates the tooth hoop.
When the 2 pins [thru the link] curl around the sprocket, it wears the one pin side down inside that roller. The rollers move 1/2 past the tooth U, because that half pass wears, causes the chain to stretch. See how the pin could not keep the roller held steady in the center? The pin is sheered off on one side, but the drawing does not show that damage. If better lubed, the pin damage is minimal and no galling off the pins. This is how you want to keep the chain well lubed at those pins inside the roller.
So look at the roller in proportion to the pin's moving. So the roller is not centered over the pin but to the right/left are those 2 wear points on the crunch/gall/sheer happening on half the pin: as it rounds the smaller sprocket and etches maximum gall/sheer around the pin.
Align: is look down at the swing arm. || This means the rear axle is square to the swing arm axle. |\ This means the rear axle is misaligned with the swing arm's axle.
Lube points: are those roller pins needing a squeezing of grease into the roller; or a dipping of links into a heavy gear oil and let that soak. There is no way chain lube can move horizontally into the pins but a good soaking and then that's only half a level flowing in, no top half being lubed like a forced squeeze or a soaking submerged.
Pin gall: is how a chain stretches; where the most critical lube point is; why you measure the pin stretch sheering off using more links; why they say the weakest galling off the pin is the weakest link.
Tooth U: is still clay, dough, putty, moving molecules you can stretch is the metal not wearing but if you sit at a light, ride over a hump? That's the tire torque as it leaves and curls that tarmac up like a mountain, you ride over that hump. Same goes for that metal stretching out 3-ways is how that tooth looks.
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