520 Chain Size Explained: Pitch, Roller Diameter & Compatibility Guide

If you ride a 250cc to 500cc motorcycle, you have likely encountered the term 520 chain size. It is one of the most popular chain sizes for small to mid-displacement bikes, but what do those three numbers actually mean? This guide breaks down the 520 chain size in plain English, covering pitch, roller diameter, and inner width so you can replace your chain with total confidence.

What Does 520 Chain Size Actually Mean?

The number “520” is not random. It is a standardized code defined by ANSI and JIS, where each digit carries specific dimensional information:

5 — the pitch code (5/8 inch or 15.875 mm)

2 — the roller diameter code (2/8 inch or 6.35 mm)

0 — the inner width code (0 = 1/4 inch or 6.35 mm)

In other words, the 520 chain size describes a chain with a 5/8-inch pitch, a 6.35 mm roller diameter, and a 6.35 mm inner width between the inner plates. These three dimensions determine whether the chain fits your sprockets and your bike’s swingarm clearance.

Pitch: The Most Important Measurement

Pitch is the distance between the centers of two adjacent pins. For a 520 chain, that distance is exactly 15.875 mm (5/8 inch). Pitch must match your sprocket tooth spacing perfectly. If you install a chain with the wrong pitch, it will not seat on the sprocket teeth, causing rapid wear, noise, and potential drivetrain failure.

How Pitch Affects Sprocket Compatibility

All 5xx-series chains share the same 5/8-inch pitch. This means a 520 chain, a 525 chain, and a 530 chain all use the same sprocket tooth spacing. The difference lies in width and roller size, not pitch. So if your sprocket is designed for a 520 chain, the pitch will match — but the width still matters.

Roller Diameter and Inner Width Explained

The roller diameter of a 520 chain is 6.35 mm (1/4 inch). The roller is the cylindrical part that contacts the sprocket tooth. A larger roller spreads load over a wider area, while a smaller roller reduces weight.

Why Inner Width Matters for Fitment

Inner width is the gap between the inner plates where the sprocket teeth sit. For a 520 chain, this is 6.35 mm. A 530 chain has the same pitch and roller diameter but a wider inner width of 9.53 mm. This is why you cannot swap a 520 and 530 chain on the same sprocket without checking clearance.

Understanding these dimensions helps you avoid the common mistake of buying a chain that is too wide or too narrow for your sprocket set.

520 vs 525 vs 530: Quick Comparison

520 chain — 15.875 mm pitch, 6.35 mm roller,