Sprockets

Q: What is a BMX Sprocket and what is its main purpose?

The BMX sprocket (or chainring) is mounted on the crank and transfers your pedaling power to the chain. Its size (number of teeth) determines how hard it is to pedal and how fast you can go (gear ratio). It also needs to be strong enough to withstand impacts from grinding and crashes.

Q: How is a BMX Sprocket constructed?

Teeth The outer ring that engages the chain. Common sizes are 25T or 28T for Freestyle, and smaller sizes (e.g., 22T) for Flatland. Bore / Center Hole The hole in the middle where the crank spindle passes through. Usually 23.8mm with adapters for 19mm or 22mm axles. Drive Hole The mounting point for the sprocket bolt (on Bolt Drive sprockets) that fixes the sprocket to the crank arm.

Q: What types of Sprockets are there?

Bolt Drive The standard system. The sprocket is fixed to the crank arm with a bolt. Compatible with almost all cranks. Spline Drive The sprocket has a hardened steel insert with teeth (Splines) that matches the crank spindle (usually 48-Spline / 19mm or 24mm). No sprocket bolt is needed. Requires a matching 48-spline spindle! Micro Drive Sprockets with fewer than 25 teeth (e.g., 22T). Primarily used in Flatland to provide clearance for tricks and an easier gear ratio. Note: Requires a specific crank mounting hole (Micro Drive bolt). Guard Sprockets Feature a built-in or replaceable guard (bash guard) to protect the chain and teeth from damage when grinding rails or ledges. Essential for street riding.

Q: What materials are used for Sprockets?

7075-T6 Aluminum The industry standard for high-end sprockets. Very hard, durable, and lightweight. Often CNC machined. 6061-T6 Aluminum Slightly softer and cheaper than 7075. Good for budget-friendly sprockets. Steel Basic stamped steel sprockets are heavy and prone to bending. They are cheap alternatives found on entry-level bikes and not recommended for serious riding. Nylon / Plastic (Guards) Often used for the replaceable guard rings on sprockets to reduce friction while grinding.

Q: Which Sprocket size (Teeth) is right for me?

The standard gear ratio for modern Freestyle BMX is 25/9 (25 teeth front, 9 teeth rear driver). However, personal preference plays a role: Sprocket Size Effect Best For 18T - 23T Easy Ratio / Clearance Flatland: Micro Drive sizes offer maximum clearance for legs/feet during tricks and a lighter gear ratio for balance moves. 25T Standard Ratio (2.77) Street / Park / Allround: Perfect balance of acceleration and top speed. Ideal for grinding (smaller diameter = more clearance). 28T Harder Ratio (3.11) Trails / Flow / Speed: Harder to pedal at start, but higher top speed. Great for big jumps and flowing lines. 30T+ Very Hard Ratio Trails / Race: For maximum speed.

Q: How do I install a BMX Sprocket?

Remove the crank arm and old sprocket. Check Spindle Size: Ensure you use the correct adapter ring (19mm or 22mm) if your sprocket bore is larger than your spindle. Alignment: Place the sprocket on the spindle. Ensure it aligns perfectly straight with the rear driver to prevent chain issues. Tighten: For Bolt Drive, tighten the sprocket bolt securely to the crank arm. For Spline Drive, simply slide it on (it locks via the splines). Reinstall the crank arm and chain.

Sprockets FAQ

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

The BMX sprocket (or chainring) is mounted on the crank and transfers your pedaling power to the chain. Its size (number of teeth) determines how hard it is to pedal and how fast you can go (gear ratio). It also needs to be strong enough to withstand impacts from grinding and crashes.

How is a BMX Sprocket constructed?

Teeth: The outer ring that engages the chain. Common sizes are 25T or 28T for Freestyle, and smaller sizes (e.g., 22T) for Flatland.
Bore / Center Hole: The hole in the middle where the crank spindle passes through. Usually 23.8mm with adapters for 19mm or 22mm axles.
Drive Hole: The mounting point for the sprocket bolt (on Bolt Drive sprockets) that fixes the sprocket to the crank arm.

What types of Sprockets are there?

Bolt Drive: The standard system. The sprocket is fixed to the crank arm with a bolt. Compatible with almost all cranks.
Spline Drive: The sprocket has a hardened steel insert with teeth (Splines) that matches the crank spindle (usually 48-Spline / 19mm or 24mm). No sprocket bolt is needed. Requires a matching 48-spline spindle!
Micro Drive: Sprockets with fewer than 25 teeth (e.g., 22T). Primarily used in Flatland to provide clearance for tricks and an easier gear ratio. Note: Requires a specific crank mounting hole (Micro Drive bolt).
Guard Sprockets: Feature a built-in or replaceable guard (bash guard) to protect the chain and teeth from damage when grinding rails or ledges. Essential for street riding.

What materials are used for Sprockets?

7075-T6 Aluminum: The industry standard for high-end sprockets. Very hard, durable, and lightweight. Often CNC machined.
6061-T6 Aluminum: Slightly softer and cheaper than 7075. Good for budget-friendly sprockets.
Steel: Basic stamped steel sprockets are heavy and prone to bending. They are cheap alternatives found on entry-level bikes and not recommended for serious riding.
Nylon / Plastic (Guards): Often used for the replaceable guard rings on sprockets to reduce friction while grinding.

Which Sprocket size (Teeth) is right for me?

The standard gear ratio for modern Freestyle BMX is 25/9 (25 teeth front, 9 teeth rear driver). However, personal preference plays a role:

Sprocket Size	Effect	Best For
18T - 23T	Easy Ratio / Clearance	Flatland: Micro Drive sizes offer maximum clearance for legs/feet during tricks and a lighter gear ratio for balance moves.
25T	Standard Ratio (2.77)	Street / Park / Allround: Perfect balance of acceleration and top speed. Ideal for grinding (smaller diameter = more clearance).
28T	Harder Ratio (3.11)	Trails / Flow / Speed: Harder to pedal at start, but higher top speed. Great for big jumps and flowing lines.
30T+	Very Hard Ratio	Trails / Race: For maximum speed.

How do I install a BMX Sprocket?

Remove the crank arm and old sprocket.
Check Spindle Size: Ensure you use the correct adapter ring (19mm or 22mm) if your sprocket bore is larger than your spindle.
Alignment: Place the sprocket on the spindle. Ensure it aligns perfectly straight with the rear driver to prevent chain issues.
Tighten: For Bolt Drive, tighten the sprocket bolt securely to the crank arm. For Spline Drive, simply slide it on (it locks via the splines).
Reinstall the crank arm and chain.

What do the specifications mean for BMX Sprockets?

Spec	Description	Examples / Available
Teeth (T)	Number of teeth. Determines gear ratio.	22T (Flatland), 25T (Street), 28T (Trails)
Bore Ø	Center hole diameter. Adapters usually included.	23.8mm (fits 19/22mm with adapter), 24mm
Type	Mounting system.	Bolt Drive, Spline Drive, Micro Drive
Material	Used metal.	7075-T6 Alu, Titanium, Steel (Cheap)
Guard	Does it have a bash guard?	No, Full Guard, Plastic Guard