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How To Determine Motorcycle Chain Size
The fastest and most accurate way to determine the size of a motorcycle chain is actually the chain itself—go directly to the 3 number (such as 520, 525 or 530) engraved on the outer side panel of the chain link.
But if the steel seal has been worn out, you have to take out the vernier caliper, by measuring two core data to verify the body: one is the “pitch” (the distance between the center of the two pin axis), the other is the “inner width ” (the distance between the two inner chain plates where the roller is located).
Take the most common “5 series” chains on the market as an example. Their pitch is 5/8 inch (15.875mm). The difference is mainly in the width (in 1/8 inches) represented by the last two digits: specifically, the width of the 520 chain is 1/4 “(6.35mm), the 525 is 5/16″(7.94mm), and the 530 is 3/8 “(9.53mm).
However, after getting these size data, don’t forget to count the number of pins in the whole chain, which determines the length of the chain. After all, the “size specification” can only tell you the model of the chain, not whether it can reach your tooth plate.
Method 1: Direct Inspection Of Side Plate Stamp
Watch this video to learn how to decode the numbers on your motorcycle chain:
Industry standards often knock the specification code directly on the metal. Before I start to take the measuring tool, I habitually take a closer look at the existing chain outer link plate.
- Clean up the chain: dirt, sludge, and accumulated chain wax on the road often cover these words. Find a piece of rag and wipe out the outer chain board.
- Find the number: stare for the three-digit number. What you see most often is nothing more than 520, 525 or 530.
- What it means: This number can directly tell you the pitch and width classification of the chain, and you don’t need to calculate it manually. If you see “520” engraved on the board, just buy a replacement chain marked 520 series, simple and clear.
Method 2: Use Caliper To Measure
This video explains how to measure the pitch of a motorcycle chain:
When we encounter an old car or a badly maintained chain, the steel seal may have worn out long ago. At this time, you must manually measure the “pitch” and “inner width” to determine the size.
For the sake of accurate data, it is strongly recommended to use a digital vernier caliper instead of an ordinary tape measure.
Pitch Measurement
“Pitch” is defined as the distance between the centers of two adjacent pins.
- How to measure: Align one claw of the caliper with the center of one pin and the other claw with the center of the next pin.
- 5 series standard: If you are measuring a standard street motorcycle chain (usually 5 series), this distance reading should be 5/8 inch (about 15.875mm). The number “5” at the beginning of “520” or “530” represents the pitch of 5/8 inch.
Measure The Inner Width
After confirming the pitch, the key to determining the specific type of chain is the “inner width”. This refers to the distance between the two inner link plates where the rollers are located.
How to measure: Put the inner measuring claw of the caliper into the inner link plate. Note that what we want to measure is the gap between the plates, not the width of the roller itself.
Interpretation width: This data can directly tell you whether the car uses 520, 525 or 530 chains.
Understanding Common 5-Series Specifications
To help you identify your chain based on your caliper measurements, refer to the specific dimensions for the most common 5-series chains mentioned in the introduction.
The logic works as follows: while the pitch remains constant, the width increases as the number gets higher.
| Chain Size | Pitch (Pin to Pin) | Internal Width (Inches) | Internal Width (Millimeters) |
| 520 | 5/8″ (15.875 mm) | 1/4″ | 6.35 mm |
| 525 | 5/8″ (15.875 mm) | 5/16″ | 7.94 mm |
| 530 | 5/8″ (15.875 mm) | 3/8″ | 9.53 mm |
530 Chain: If your width measurement is approximately 9.53 mm, you have a 530 chain.
520 Chain: If your width measurement is approximately 6.35 mm, you have a 520 chain.
525 Chain: If your width measurement is approximately 7.94 mm, you have a 525 chain.
Chain Series
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Determining Chain Length
Knowing whether your chain is “520” or “530” is actually only half of the work. This number refers to the “type” of the chain, it does not represent the “length”. In order to ensure that the new chain is perfectly suitable for your car and tooth ratio configuration, you must determine the total number of chain links.
- Number of pins: The safest way to determine the length is to count the number of pins (sometimes called rivets) on the existing chain.
- Why length is important: Even if both cars use 520 chains, one may need 112 knots due to the different length of the rear rocker arm or the size of the tooth plate, while the other may need 120 knots.
- Ordering advice: When placing an order, it is usually safer to buy a chain that is slightly longer than the number of sections you counted. Because you can use the chain cutting device to remove the extra chain links and achieve a perfect match. But if you buy a short one, it is absolutely impossible to safely “lengthen” the chain.
By combining the pitch and width measurements to find the chain type (e. g. 525), and then determining the length by counting the pins, you have all the data you need to accurately replace the motorcycle chain.
About the Author
As a dedicated motorcycle mechanic and enthusiast, I know that getting the right parts starts with precise measurements. I wrote this guide to help you look past the rust and grease, teaching you exactly how to use a caliper to measure pitch and width so you can determine your motorcycle chain size with confidence.