Forks

A BMX fork is the two-legged part that holds the front wheel and connects it to the frame through the head tube. The legs carry the wheel, the steerer tube rotates in the headset, and the stem clamps to the top of the steerer.

What it does

The fork steers the bike, supports the front wheel and takes the shock of landings and impacts. Its design affects how the front end feels when you turn, lean or ride a nose manual.

Offset (rake)

Offset is how far the front axle sits ahead of the steering line, measured in millimetres. It changes the trail, which is the distance between where the steering line meets the ground and the tyre contact patch.

• Lower offset (around 20 mm) gives more trail. The bike feels steadier at speed and wants to run straight.
• Higher offset (around 28 to 32 mm) gives less trail. The steering feels lighter and quicker. Many riders say it makes nose manuals feel easier and the front end more forgiving, since the wheel sits further forward.
• 25 mm is the common middle ground.

None of this is dramatic. Offset works with head tube angle, so a small change in one can be balanced by the other.

Types and standards

Leg shape

• Straight legs. Simple and light. Used on budget and older forks.
• Tapered legs. Thicker at the crown and thinner at the dropout. This keeps strength where it is needed and saves weight lower down. Most mid and high-end forks use tapered legs.

Dropouts

The dropouts are the slots at the leg ends that take the axle. Two widths are common:

Dropout	Matching axle	Notes
10 mm (3/8 inch)	3/8 inch axle	Common on budget and older setups. Lighter.
14 mm	14 mm axle	Stronger. Common on mid and high-end builds.

The dropout slot must match the front hub axle. Some forks come with a spacer to fit both.

Steerer tube and bearing race

The steerer is the tube at the top of the fork. The BMX standard is 1 1/8 inch (28.6 mm) and threadless, so the stem clamps on the outside. The fork needs a crown race at the base of the steerer to seat the lower headset bearing. For integrated headsets, the fork crown race seat is sized to match the headset. Your headset kit usually includes the correct race.

Materials

Chromoly is the standard. It is tough and handles impacts well. Some race forks use aluminium or carbon fibre to save weight.

Sizing and compatibility

• Steerer length. Forks ship with a long steerer. Cut it to suit your stack: head tube, headset, spacers and stem. Measure twice. Leave the steerer about 2 to 3 mm below the top of the stem so the top cap can pull down.
• Axle-to-crown height. Taller forks raise the front end and slow steering. Shorter ones do the opposite. Check the frame geometry before swapping.
• Tyre clearance. Wider tyres need enough gap between the legs. Check the fork's stated clearance.
• Brake and pegs. If you plan to ride front pegs or a front brake, check the fork has the right mounts or clearance.

How to choose

1. Pick the steerer standard first: 1 1/8 inch threadless is the BMX default.
2. Match the dropout width to your front hub axle, or buy both together.
3. Choose offset by feel. If you do not know, 25 mm is a sound start.
4. Pick tapered legs if you want a good balance of weight and strength.
5. Check the crown race and headset match before you cut the steerer.

Maintenance

• Inspect the legs and dropouts for cracks, bends and worn slots, especially after hard landings.
• Keep the axle nuts tight, so the wheel cannot shift in the dropouts.
• Check the steerer and stem clamp area for cracks.
• Replace a bent fork. Straightening weakens the metal.

Related parts

• Frame geometry: head tube angle and fork offset work together.
• Headset: the fork rotates in it.
• Stem: clamps to the steerer.
• Front hub: sits in the dropouts.
• Nose manual: a trick affected by fork offset.