BMX Race Rims

What is a BMX Race Rim and what makes it special?

The Race Rim is the outer ring of your wheel and defines the tire size and stability. Unlike freestyle rims, race rims are designed for the best possible Stiffness-to-Weight Ratio. Every gram saved on the rim reduces rotational mass, making your acceleration out of the gate significantly faster. Modern rims are often "Tubeless Ready" or specifically optimized for disc brakes (without brake tracks).

How is a BMX Race Rim constructed?

Double Wall

The standard for race rims. Two layers of material providing high stiffness and stability against impacts.

Brake Surface (Flanks)

Machined (Silver): For rim brakes. The CNC-machined surface ensures optimal braking power.
Disc Specific: No brake track. Clean look and aerodynamic shape, designed exclusively for disc brake hubs.

Eyelets

Metal inserts in the spoke holes that reinforce the rim and prevent the spoke nipples from pulling through under high tension.

Overview Table: BMX Race Rim Sizes & Use Cases

Key measurements for BMX race rims include the ETRTO diameter (e.g. 406mm or 451mm) and the rim width, which determines which tires will fit. Below is an overview of the most common combinations used in BMX racing.

Technical Definitions: ETRTO & ERD

ETRTO (European Tyre and Rim Technical Organisation)

A standardized size specification ensuring compatibility. The number consists of two parts (e.g., 16-451):

• First number (16) = Tire width in mm.
• Second number (451) = Inner diameter of the rim in mm (where the tire seats).

Tip: In our shop, filter by "ETRTO Diameter" to find the right rim.

ERD (Effective Rim Diameter)

The "Effective Rim Diameter" is the diameter of the rim base measured between opposite spoke holes. This value is essential for calculating spoke length. It tells you how long the spokes need to be to reach through the rim.

Special Focus: OS20 – 20" but Bigger!

What is OS20?
OS20 is a 20-inch BMX wheel size with a larger diameter of 451 mm (compared to the usual 406 mm for 20"). It offers similar widths to standard 20" race wheels.

Are OS20 tires and rims compatible with Expert sizes?
No. OS20 tires and rims are not compatible with the narrower 451mm rims used in Junior/Expert setups.

Is OS20 allowed in BMX racing?
Yes, OS20 wheels and tires comply with UCI BMX sizing regulations for 20".

What parts do I need for OS20?
You will need an OS20-specific frame, OS20 wheels, and OS20 tires (including OS20 rim tape and OS20 tubes). Many standard 20" forks are compatible.

What are the advantages of OS20?
OS20 rolls faster and carries momentum better due to a stiffer tire casing and smaller contact patch. This can translate into higher top speed and improved efficiency when maintaining speed.

Which materials are used?

Aluminum 6061-T6

The reliable standard. Light, stiff, and affordable.

Carbon Fiber

The High-End choice. Extremely stiff and ultra-light. Carbon rims transfer power more directly than aluminum but are significantly more expensive.

How do I assemble a wheel?

1. Calculate Spoke Length: Use the ERD of the rim and the flange dimensions of your Hub.
2. Lacing: Insert the Spokes according to the desired pattern (usually 3-cross for Pro, sometimes radial for Mini fronts).
3. Tensioning: Tighten the nipples evenly. A true race wheel needs high, even spoke tension for direct power transfer.
4. Truing: Eliminate lateral and vertical wobbles.

What do the specifications mean?