Older mountain bikes often used a 3× setup: three chainrings up front and a cassette in back. Riders picked a front ring for the climb or descent, then fine-tuned with the rear cogs.
Most modern trail and race bikes use a 1× drivetrain — a single front chainring paired with a wide-range cassette (for example 12 speeds). There is no front shifter to manage; gear range comes from the big spread of rear cogs. That simplifies shifting on technical climbs and matches how most NICA race bikes are set up today.
Stub — add diagrams and “what to buy used” notes later.
