Cranks

What is a BMX Crank and what is its main purpose?

The BMX crankset connects your pedals to the bike and transfers your pedaling power to the chain. It has to be incredibly strong to withstand drops, landings, and grinding. Modern freestyle cranks are almost exclusively 2-piece or 3-piece designs, compatible with Mid BB or Spanish BB standards.

How is a BMX Crank constructed?

Crank Arms

The two levers where you attach your pedals. They usually feature a boss for the sprocket bolt (unless Spline Drive).

Spindle (Axle)

The shaft connecting the two arms through the bottom bracket. Common diameters are 19mm (standard), 22mm (stiff), and 24mm (ultra-stiff).

Splines

The teeth on the spindle that engage with the crank arms. 48-Spline is the industry standard for high-end cranks (allows micro-adjustment), while 8-Spline is common on entry-level bikes.

Spindle Bolts

The bolts that hold the arms onto the spindle.

What types of BMX Cranks are there?

3-Piece Cranks

The most common and robust design. Consists of two separate arms and one spindle. If one part breaks, it can be replaced individually. Great for street and heavy abuse.

2-Piece / 2.5-Piece Cranks

One crank arm is permanently welded to the spindle (2-piece) or pressed on (2.5-piece). This reduces weight and simplifies installation (fewer bolts).

1-Piece Cranks

Old-school design found on cheap kids, beginners bikes or vintage rides. Not suitable for modern freestyle riding.

Race Cranks

Designed for maximum stiffness at minimum weight (often aluminum or carbon). These are optimized for speed on the track and are not suitable for freestyle tricks.

Key Features & Compatibility

RHD / LHD / RHD & LHD

Refers to the drive side. RHD (Right Hand Drive) is standard. LHD (Left Hand Drive) places the sprocket on the left, which is useful if you grind on the right side to protect the drivetrain. Most modern 3-piece cranks are compatible with both (RHD & LHD).

Spline Drive

A system where the sprocket is not fixed with a bolt, but engages directly with the 48-spline profile of the spindle. Requires a matching 48-spline spindle and a Spline Drive sprocket.

Micro Drive Compatible

Refers to cranks that have mounting holes for very small sprockets (usually under 23T), often used in Flatland riding.

What materials are used for BMX Cranks?

4130 CrMo (Chromoly)

The standard material. Heat-treated CrMo is incredibly strong and resistant to bending.

Titanium

Used for high-end spindles or complete cranksets. Titanium is about 40-50% lighter than steel but extremely strong and corrosion-resistant. The ultimate upgrade for weight weenies (but expensive).

Aluminum

Rare in Freestyle (sometimes used for crank arms with steel inserts), but standard in BMX Race due to low weight.

Which BMX Crank is right for my needs?

Besides the axle diameter (make sure it fits your Bottom Bracket!), the Crank Arm Length is the biggest factor.

How do I install a BMX Crank?

1. Install the Bottom Bracket bearings into the frame.
2. Grease the spindle and slide it through the bearings (use the internal spacer!).
3. Install the sprocket (ensure alignment with the rear driver).
4. Slide the crank arms onto the splines. Make sure they are at 180° to each other.
5. Tighten the spindle bolts evenly. Ensure the crank spins freely but has no side-to-side play.

How do I maintain my BMX Crank?

• Grease is key: Keep the splines and pedal threads greased to prevent annoying creaking noises.
• Check bolts: Spindle bolts can loosen over time. Check them regularly.
• Pedal washers: Always use pedal washers between the pedal axle and the crank arm to protect the material.

What do the specifications mean for BMX Cranks?