Stretch marks in the chain happen two ways. One is short, the other is a pin wearing process. That is why you take an average of 21 pin lengths, then measure against the factory number on the final wear distance.
Just remember when the chain is made, there is that grease around the inside of the pin and roller. That is squeezed out of the o-rings on the thrust alone. So, there is one loose chain times 106 links about to lose their lube around the pin. That is the one quick and fast stretch in the beginning.
The chain only moves 1/2 way around the sprockets. This is especially around the counter shaft sprocket. It is almost half way around. At one time, you could roll over the lube and not cut into the material of the inner pin. The outer roller and inner pin wear on each other. Now you have these two rubbing against each other no matter if lubed or not. The lube just slows down that pin being rubbed away.
And if you lined the pins all up, there would be one pin with a weak bond to the molecules. This is the one that will break at that wear point. The stress crack has begun somewhere along that weak molecule bonding of that pin. It breaks like glass and makes that line to the end of the stretch of molecules and then, POP!
Off, goes the chain. That friction is still occurring. You need to count 21 pins, then measurement like a tire [wear] block in a rain groove channel. Once you touch it, the tire is done. Once you reach 323 mm (12.7 in.) at the chain pin length, she is played and so are the sprockets.
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I'm going to groom you, Rookie, into thinking common sense applications. Guys will take grease, slap some in their palm then pack a bearing? I take a plastic baggie, corner a blob of grease, drop the bearing in that same corner, twist both together in that pressure/vacuum, I coat a lot more under pressure, yes or no?
So, here I am taking grease in my palm and now squeeze the grease in whatever pressure I can get that grease to go into. Chain lube sprays over the parts like rain on a roof. I take grease and jam them into the openings like a flood, it fills the house to the roof. Whatever was in the way was squeeze out and the grease is in there now. Yes or no?
Tormenting the motorcycling community one post at a time