If I replace the cassette on my road bike, should I replace the whole drivetrain? Relatively new to road cycling, have bought a 2nd hand bike and am thinking some parts of the drivetrain need replacing. Have tried to find this online and can't find any answers. Thanks!
If the new cassette has the same gears (# teeth) as the old one, you may not need to. If your chain is worn or in bad shape, this would be the time to replace it. If the new cassette has a different number of teeth in the larger cogs, you may need to lengthen or shorten the chain.