Originally Posted by
cyclotoine
This forum is full or unqualified statements like this. This is a subjective opinion with no explanation.
My experience is you can break a shimano chain as many times as you wish. Just be sure to only break factory pins and never a replacement pin and always use a replacement pin. I use shimano chains on campy, sram and shimano bikes. Why? I feel personally that they are quieter, shift better and last longer. That is my opinion based on my years or riding and time spent working on 1000s of bikes in a shop full time from 2008-end of 2011. Have things changed? Possibly and probably, but I am sure new 8/9 and 10 speed shimano chains are the same as ever. Use a replacement pin, it's super easy to use, follow the instructions and you won't have any trouble.
I did the above and subsequently 'broke' a shimano chain, which then got caught up within the rear derailleur and pulled it around the axle. One of the pins pulled through the plates and spread the plates apart causing them to bind in the derailleur. All I'm saying is be careful, I'm not saying to not do it. User error can have...detrimental effects (as in my case). The thinner the chain, the thinner the plates, and the less purchase they have on the pins.