According to: http://www.sram.com/sram/road/technologies/powerlock
"SRAM chain engineers developed PowerLock as a tool free, sure and consistent way to connect our 10 speed chains. While PL does not require special tools for install, the especially tight tolerances of 10 Speed drive trains mandated that each PowerLock is good for a one-time application only."
According to: http://www.competitivecyclist.com/sram-pc-1051-chain
The SRAM PC-1051 Chain is compatible with both SRAM and Shimano 10-speed drivetrains. Please note that while the PowerLock installation can be done tool-free, it's recommended to be used only once due to the extremely close tolerances required by the narrow 10-speed design. So if you must break your chain for maintenance reasons, a new 10-speed PowerLock link will be required to reassemble it.
- Why is this the case?
- Have people hear observed or seen tests about what happens if you re-use?
I use the Park Tool Master Link Pliers to remove master links. I have a hard time believing that doing it that way stresses it significantly.
Related, from http://www.bikeradar.com/us/mtb/gear/article/trail-tech-mastering-master-links-36757/:
"According to SRAM, the ridge that joins the two plates of the PowerLock together can be damaged when unlocking it, increasing the risk of failure if reused. So yes, if you choose to reuse a PowerLock there is an increased likelihood of if failing, according to SRAM."
I know a number of professional and team mechanics who routinely reuse PowerLocks on their own bikes, but replace them with a new link when dealing with a customer or athlete, so it’s a bit of “do as I say, not as I do.”