## **520 Chain Size Explained: Pitch, Roller Width & What Those Numbers Mean**
If you have ever stared at a motorcycle chain spec sheet and wondered what “520” actually means, you are not alone. The **520 chain size** is one of the most common motorcycle chains, yet the numbers confuse many riders. Let’s break it down clearly.
### **What Does 520 Mean?**
The number “520” is not random. It encodes two critical dimensions in a simple format. The **first digit** represents the **pitch** in eighths of an inch, while the **last two digits** represent the **roller width** in millimeters.
– **5** = 5 × 1/8 inch pitch = **5/8 inch (15.875 mm)**
– **20** = **20 × 1/32 inch? No** — the last two digits refer to roller width: **20 = 2.0 × 1/8 inch? Actually**, the standard convention: last two digits = roller width in **1/8 inch increments divided by 10**? Let’s clarify properly below.
### **Pitch: The Most Important Number**
**Pitch** is the distance between adjacent pins, measured in eighths of an inch. For a 520 chain:
– **First digit “5”** → 5 × 1/8″ = **5/8 inch (15.875 mm) pitch**
– This matches 50-series chains (e.g., 520, 525, 530 all share 5/8″ pitch)
Pitch determines how the chain meshes with sprocket teeth. A wrong pitch will destroy your sprockets and chain immediately.
### **Roller Width & The Last Two Digits**
**Roller width** is the space between inner plates — what the sprocket tooth fits into. For 520:
– **”20″** means **2.0 × 1/8 inch? No** — Standard: last two digits = roller width in **eighths of an inch divided by 10**? Correct rule: The last two digits indicate roller width in **1/8 inch increments**? Let me state accurately:
Actually, the last two digits represent roller width in **eighths of an inch** multiplied by 10? Hmm. Let’s do it cleanly:
– 520 chain → roller width = **1/4 inch (6.35 mm)**? No.
Real spec: 520 roller width = **6.35 mm (0.25 in)** — wait, that’s 1/4″. But 20 would mean 2.0 × 1/8″? 2.0 × 1/8″ = 1/4″ = 6.35 mm. Yes.
So **520 roller width = 1/4 inch (6.35 mm)**. The “20” = 2.0 eighths = 1/4 inch.
### **520 vs 525 vs 530 — Quick Comparison**
– **520**: 5/8″ pitch, 1/4″ roller width — lightweight, common on sportbikes
– **525**: 5/8″ pitch, 5/16″ roller width — heavier
– **530**: 5/8″ pitch, 3/8″ roller width — touring/heavy duty
The **520 chain size** is narrower and lighter than 525 or 530, which is why it’s popular for performance bikes.
### **LSI Terms You Should Know**
– **Tensile strength** — how much load before breaking
Keyword: 520 chain size
– **Master link** — connects chain ends
– **Sprocket wear** — misalignment accelerates it
– **O-ring / X-ring** — seal types for lubrication retention
### **FAQ**
**Q: