How-To Guide — Chain Wear Measurement

How to Measure Motorcycle Chain Wear
The Complete Method

A chain can look clean and rust-free while being significantly beyond its replacement threshold. The only reliable wear indicator is the 20-link measurement — a steel ruler and five minutes. This guide covers the correct technique, the critical reference numbers, and the checks that go beyond the ruler.

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Why Visual Inspection Is Not Enough

A motorcycle chain that is clean, well-lubricated, and shows no rust can still be at or beyond its replacement threshold. The wear that determines a chain’s remaining service life happens at the pin-bushing interface inside each joint — a surface that is not visible from the outside and does not change in appearance as the joint wears. The chain’s external appearance tells you nothing about its internal wear state.

JIS B 1801 — the standard that governs all motorcycle chain dimensions — defines the replacement threshold as 3% elongation above nominal 20-link length. This is the point at which the chain’s effective pitch has increased enough to compromise sprocket tooth engagement geometry. Beyond this threshold, the chain rides progressively higher on the tooth faces, accelerating both chain elongation and sprocket wear simultaneously.

What You Need

1A steel rule or tape measure — minimum 350 mm length
2A centre stand or rear paddock stand — to allow wheel rotation
3This guide’s reference numbers — or the service manual’s chain specification

A dedicated chain wear indicator tool (pin-gap gauge) makes the measurement faster, but a steel rule is equally accurate when used correctly.

The Reference Numbers — 20-Link Nominal and Replacement

Chain Series Točka glasa 20-Link Nominal Replace at (3% threshold) Plan at (2.5% — early warning)
415 · 420 · 428 12.700 mm 254.0 mm 261.6 mm 260.4 mm
520 · 525 · 530 15,875 mm 317.5 mm 327.0 mm 325.4 mm

The “plan at” figure gives you roughly 1,000–3,000 km warning to order and schedule replacement before the chain actually reaches the limit — useful for avoiding a rushed emergency chain order.

motorcycle chain dimension diagram pitch inner width pin centre measurement point for 20-link elongation test

The 20-Link Measurement — Step by Step

1

Support the motorcycle and find the tightest point

Place the motorcycle on its centre stand so the rear wheel rotates freely. Slowly rotate the rear wheel one full revolution while pressing upward on the chain at its midpoint between the two sprockets. The position where chain upward movement is minimum is the tightest point.

Why the tightest point matters: Chain wear is not perfectly uniform — minor sprocket runout causes the chain to have slightly different tension at different positions. Measuring at the tightest point captures the minimum slack condition that the chain operates at in actual use. Measuring anywhere else gives a falsely optimistic slack reading and may allow you to continue riding an unsafe chain past its actual elongation threshold.
2

Select a 20-link section on the lower chain run

On the lower run of the chain (the section between the bottom of the rear sprocket and the front sprocket, visible from the side of the machine), select any 20 consecutive links. The master link is a convenient reference point — start from one side of the master link and count 20 links along. Mark the start and end pins with a marker or chalk if needed for clarity.

Avoid measuring across the top run of the chain (the tight side under drive loading) or across the sprockets — these positions make accurate pin-centre placement difficult.

3

Place the ruler pin-centre to pin-centre — under light tension

Place the ruler so that its zero mark sits at the centre of the first pin, and read the measurement at the centre of the 21st pin (which is the 20th link further along). The measurement should be taken with the chain under light natural tension — the weight of the chain itself in the lower run is sufficient. Do not pull the chain tight while measuring, and do not let it sag freely either.

Measuring tip: The pin centres are visible at the outer edge of the outer link plates. Sight along the ruler from directly above — parallax error from reading the ruler at an angle can introduce 1–2 mm of reading error, which is significant given the 9.5 mm total replacement range for a 15.875 mm pitch chain.
4

Record the measurement and compare to the threshold

Record the reading in millimetres. Compare it to the pitch-appropriate threshold:

✓ Below 260 mm (428) / 325 mm (520)
Chain is within safe limits. Record reading and continue monitoring at next service interval.
⚠ 260–261.6 mm (428) / 325–327 mm (520)
Order replacement now. Plan service before threshold is reached. Inspect sprockets.
✗ Above 261.6 mm (428) / 327 mm (520)
Replace before next ride. Do not delay — sprocket damage is accelerating rapidly.
5

Track measurements over time

Keep a simple record of each measurement date and reading. A chain that gains 0.5 mm per 1,000 km is on a predictable trajectory; one that gains 2 mm per 1,000 km is elongating faster than expected — investigate the cause. This record also gives you advance warning: at 0.5 mm per 1,000 km with 4 mm remaining before the threshold, you know replacement is needed in approximately 8,000 km and can plan accordingly.

Beyond the Ruler — Four Additional Wear Checks

The 20-link measurement is the primary and most reliable wear indicator, but four additional checks should be performed at each measurement inspection. These can identify problems that the elongation measurement alone will not catch.

① Stiff Link Check

Flex each link laterally by hand as you work around the full chain circuit. Every link should flex freely side-to-side within its design range. A link that resists lateral flex, or that feels stiff in articulation, is either kinked (damaged pin) or corroded at the joint.

Stiff link = replace now, regardless of elongation measurement

② Rear Sprocket Tooth Profile

View the rear sprocket tooth profile from the side. New teeth are symmetrical. Worn teeth develop a “hook” on the leading face (the face chain tension acts against). Asymmetric or hook-shaped teeth indicate the sprocket must be replaced — a new chain on hook-worn sprockets will reach replacement threshold in half the normal distance.

Hook teeth = replace sprocket with chain

③ Seal Condition (Sealed Chains)

On O-ring, X-ring, and Super X-ring chains, visually inspect the rubber seals visible between the inner and outer plates at a selection of joints. Seals should be round or X-shaped in cross-section and maintain their form when viewed from the side. Cracked, flat, or missing seals indicate the seal has failed at those joints.

Multiple damaged seals = replace chain

④ Tooth Root Pullaway Test

At the rear sprocket, try to pull the chain away from the sprocket by hand while it is on the teeth. A correctly-fitting chain sits firmly in the tooth valley and can only be lifted slightly. A chain that can be pulled far enough from the sprocket to expose more than half the tooth root height is severely elongated — the rollers are no longer seating correctly.

Significant tooth root exposure = replace immediately

motorcycle chain wear measurement inspection 20-link elongation test ruler method checking chain condition

Keeping a Chain Measurement Record

Recording each measurement date and reading takes 30 seconds and gives you two things: a trend that predicts when the chain will need replacement, and a history that reveals if the elongation rate has suddenly increased (which is a diagnostic signal that something has changed — a contamination event, a change in lubricant quality, or a sprocket beginning to hook-wear).

Sample Measurement Record — 520H-X Chain (nominal 317.5 mm)
Date Odometer 20-Link Reading Above Nominal Status
New install 0 km 317.5 mm — ✓ New
3 months 3,000 km 318.8 mm +1.3 mm ✓ Good
6 months 6,000 km 320.1 mm +2.6 mm ✓ Good
9 months 9,000 km 322.0 mm +4.5 mm ✓ Good
12 mjeseci 12,000 km 324.2 mm +6.7 mm ⚠ Order replacement
15 months 15,000 km 327.1 mm +9.6 mm ✗ Replace now

Chain at Replacement Threshold? All Sizes In Stock

Once your measurement reaches the replacement threshold, the chain must be replaced before the next extended ride. All pitches in stock — dispatch within 3–7 business days.

Standard — 420 / 428 / 520 / 525 / 530
Non-sealed · Lowest unit cost

 

O-Ring Sealed — All Pitches
Solid bore · 2–3× standard life

 

X-Ring Sealed — All Pitches
34.0 kN · 3–4× standard life

 

Inspect sprockets at replacement time — usklađeni lančanici za motocikle za sve terene.
Lančanici →

Često postavljana pitanja

Do I need a special chain wear tool or will a ruler work?+
A 350 mm steel ruler is equally accurate to a dedicated chain wear indicator when used correctly. Dedicated chain wear gauges (pin-gap tools) are faster because they do not require counting links or finding pin centres — the gauge pins simply drop into the chain rollers and indicate pass/fail. Both methods produce the same conclusion when used correctly. If you perform chain measurements regularly, a dedicated gauge is a convenient time-saver.
The measurement varies each time I check. Which reading should I use?+
Variation between readings at different chain positions is normal — chain wear is not perfectly uniform. Always use the measurement taken at the tightest point (minimum slack position during a full wheel rotation). If you also measure at other positions and find variation of more than 3–4 mm between the loosest and tightest readings, this indicates significant wear unevenness — possibly a damaged section or stiff link — and the chain should be replaced regardless of whether the tightest-point reading has reached the threshold.
My 520 and 525 chains have different nominal pitches — are the measurements different?+
No — 520, 525, and 530 all share the 15.875 mm pitch. The 20-link nominal length is 317.5 mm and the replacement threshold is 327.0 mm for all three. The difference between 520, 525, and 530 is inner width (6.35 / 7.94 / 9.53 mm), not pitch — pitch is identical across the family. The measurement method and thresholds are therefore identical for all three.
How frequently should I measure chain wear?+
Every third or fourth lubrication service is a practical rule — for a standard chain lubricated every 500 km, this means measuring every 1,500–2,000 km. For a sealed X-ring chain lubricated every 1,000 km, measuring every 3,000 km is reasonable. Once the chain reaches 75% of its estimated service life, increase measurement frequency to every lubrication event to catch the threshold before it is missed.

Measured and Ready to Replace?

Korea Ever-Power stocks all motorcycle chain sizes — 420 through 530, standard through Super X-ring — with dispatch within 3–7 business days. Send us the size number from your chain plate and we confirm the replacement specification.

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