Bought myself a chain wear tool as I will be looking to replace my chain and cassette myself once they get a bit worn. Do I replace at 0.75% wear or 1%? The "tooth" doesn't quite fall all the way into the space between links at 0.75% but does with a little bit of pressure (only a little). Also my cassette was replaced with the last chain change at the start of September so should I replace that as well or wait until the next chain?? Any help really appreciated.