Chain wear: replace at 0.5% on 11- and 12-speed and 0.75% on 10-speed, before the cassette pays for it
Replace a chain by the time it has stretched 0.5% on an 11- or 12-speed drivetrain, or 0.75% on 10-speed or fewer: those are Park Tool's general replacement points and the marks on its checker. A worn chain left on the bike wears the cassette and chainrings with it, and a cassette costs far more than a chain. Where your chain maker publishes its own figure, that figure takes precedence.
The replacement points and the ruler check
Park Tool's guide, dated 17 February 2017, gives these replacement points: 1.0% elongation for single-speed, 0.75% for 10-speed cassettes or fewer and 0.5% for 11-speed or more. Its CC-4.2 checker marks all three and fits 5- to 12-speed chains, SRAM AXS 12-speed included. Without a checker, line a rivet up with zero on a ruler and count 24 rivets: the last should sit on the 12-inch mark, and more than 1/16 inch past it means the chain is due. Park adds that each drivetrain maker has its own specification, so use your chain maker's figure where it publishes one; there is no dependable kilometre interval.
SRAM’s 2023 compatible-tool sheet names checker models, including Park CC-4. Read it as tool compatibility, not a wear-limit chart: confirm the current replacement instruction for your chain separately.
Keep a small service record
For a GRARO build, record chain code, installation date, checker model and readings from several positions according to the tool instructions. Check more attentively when riding conditions become dirtier or wetter. Clean and lubricate using the drivetrain maker’s method, keeping lubricant away from disc-brake surfaces.
At the replacement point, buy the correct chain and joining link, and verify sizing rather than assuming the old chain was correct. Save the measured result. That record is more useful than “it looked a bit tired” if you later need to explain premature wear.
Skipping needs diagnosis
If a new chain skips under load, have compatibility, setup and cassette condition checked; do not ride through unpredictable slipping. A worn cassette is one possible cause, not the only one. Price the exact cassette replacement when choosing a drivetrain in the first place: a low purchase price and a high consumables bill can coexist.
Use the component compatibility check before ordering replacement parts, and keep the cassette tooth sequence with the service record.
Sources
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