Originally Posted by
HillRider
Incidentally, Shimano rear derailleurs have their guide pulleys with the built in sideplay engraved "Centeron" meaning they self-center under the chosen cog.
The Centeron™ design is pretty brilliant. I put 10-speed shifters on my bike with an 8-speed cassette. There were two gears that required two shifts to get into, but other than that, it worked flawlessly because of that feature. Shifting and pedaling were silent.
I decided to replace the cassette, so now I have a true 10-speed system.