Originally Posted by
Racing Dan
Good question. Who came up with these values and why. Industry standard is 1% and there is no logical reason it why it’s either 0.5% or 0.75% depending on 10s vs 11s. In shimano cassettes the actual cogs are identical in 10s vs 11s. Only spacing and # of cogs differ slightly. Not to mention it’s unclear if its 0.5% actual elongation or roller wear should be included. Park used to have a tool that included roller wear, now they have one that doesn't, but the recommended values stay the same even if different methods give very different results. Makes no sense what so ever.
SRAM says to replace at 0.8% without specifying cassette speeds. KMC says to replace the chain between 0.75% and 1%, again, without specifying speeds. I can’t find anything from Shimano. Park Tool says to replace 10 speed and below at 0.75% and 11 speed and above at 0.5%. Pick your poison.
The rule method, by the way, replaces chains at 0.5%. 0.75% would be 3/32” and 1% would be a full 1/8”.
11 speed and above chains are thinner with regards to overall width. Perhaps the thinking is to replace them at 0.5% since the pressure on the pin is greater.