I have a two year old Shimano 105 5603 triple drivetrain on my bike. This drivetrain now has about 8000 miles on it. I’ll soon be replacing, for the second time, the chain. I was going to replace the cassette at the same time; I don’t want to shorten the life a new chain by installing it on worn cogs.
However the cassette looks like new. The bike also shifts well and I don’t have any problems with the drivetrain.
Does a cassette show wear? Should I change it anyway, based on 8000 miles of use?