Measure saddle-to-bar reach and drop

Set your saddle height and setback first: the handlebar position is measured from the saddle, and every saddle change throws the measurement off. Then stand the bike on a flat floor, tyres inflated, against a wall or in a work stand, front wheel straight.

Find where on the bar your hands rest most of the time: the brake hoods on a drop bar, the grips on a flat bar. That is the point you are going to measure to.

Stretch the Tape measure (or else Steel ruler) in a straight line from the nose of the saddle to the middle of where your hands rest. Write the distance down in millimetres.

Take the same measurement on the other side of the bar: both values should match. A difference of more than a few millimetres means the bar has rotated in the stem or the levers are mounted crooked.

Lay the Steel ruler (or else Tape measure) flat across the saddle, halfway along its length, and measure the height from the top of the saddle to the floor. Then measure the height from the top of the handlebar to the floor, where your hands rest.

The difference between the two heights is the saddle-to-bar drop. Note which way it goes, too: bar lower or higher than the saddle.

Common starting values, to adapt to how flexible you are: on a road bike, bar 4 to 10 cm below the saddle; on a gravel bike, 2 to 6 cm below; on a mountain bike, roughly level, within 2 cm either way; on a city bike, 0 to 6 cm above the saddle. A kids' bike keeps the bar between 2 cm below and 4 cm above.

Numb hands, a sore neck or a sore lower back often mean the bar is too low or too far. A bike that feels twitchy, or a very upright position that tires your back on climbs, points the other way.

To raise or lower the bar on a threadless stem, loosen the stem clamp bolts and then the top cap with the Allen keys (or else Multi-tool), move spacers from below the stem to above it or the other way round, then refit the top cap. Flipping the stem also changes the height. To bring the bar closer, you need a shorter stem.

Set the headset by tightening the top cap just enough, line the stem up with the front wheel, then tighten the stem bolts in turn to the torque printed on the stem, using the Torque wrench. Change one centimetre at a time and ride before going further.