^ +1, a new chain or cassette often works well with a old chain or cassette even on the work stand. However, hand cranking under no load generates an insignificant amount of torque compared to what the drive system experiences on the road. Only a road test will reveal wear related incompatibility. Unfortunately, shop mechanics do not have the time to conduct road tests on repairs and even if they did, customers would rant over the extra cost. Consequently, a certain amount of repair returns are cost of doing business.