"training bike" versus "racing bike"
"Back in the day" it was common to have a "racing bike", or at least "racing wheels", and a set-up more generally used for training. The idea was the training bike would take more wear & tear, while the racing bike was kept in more refined condition for racing where small efficiency gains were truly important. Examples of tradeoffs include: cost: given a fixed amount of wear & tear or damage risk, it's better to use a cheap part than an expensive one, since the cheap one is easier to replace. Examples of this include wheels, cassettes, and chains: these parts wear out (wheels from rim brakes, drivetrain from normal use) and if the performance gains of expensive stuff aren't important in a particular ride, it makes sense to go with the cheaper parts for these. reliability: lighter parts tend to be less reliable, with less wear life, so even at the same cost (which they're not) it makes sense to stick with more durable stuff if the t...