I noticed that my rear spocket had weird teeth wear after I estimated about 3000 miles on my coaster brake trek that was causing sounds from my bottom bracket.
After I greased my bottom bracket and replaced my rear wheel I still used my original rear sprocket(gear) because I replaced my chain in time,but after closer examination I notice on the inside of the teeth where the top of the chain rollers would be is a point,like when the chain rolls off the rear sprocket it would cause a sound from most of the teeth,from rolling over the points.
I turned the original gear over,despite the chainline a little off,it doesnt do it any more.
Is this weird sprocket wear?it would appear that the chain was crushing the insides of the metal sprocket creating a point on the inside of the teeth(best I could describe it).The front crank is fine.
I think so,when the chain leaves the sprocket it makes a sound(sounds like the bb),I flip the gear over(you can do that) and all sound stop.On my feet with the sound it feels like something may be hooking on something.a sharp point on the inside of the teeth,also when I noticed it originally I belt sanded the sharp point down,and it got better but still there,then I turned the gear over and stopped completely. I know a worn chain causes points but this was not the kind of point that I seen on sheldon browns website.