Chain Checkers
Browse used chain checkers for sale from riders across the UK. A chain checker measures elongation against the 12.7mm nominal pitch of a bicycle chain and tells you when it has passed the 0.5% limit most 11 and 12-speed drivetrains work to, or the 0.75% that 8, 9 and 10-speed chains will tolerate. It is for anyone who would rather replace a chain on time than replace the cassette and chainrings with it.
How does a chain checker work?
A new chain has its rivets exactly half an inch apart. As the pins and bushings wear, that spacing grows, and the gauge measures the gap over a fixed span of links — when the far end drops in, the chain has passed the marked percentage. Percentages are small by design: 0.5% over 12 links is under a millimetre, which is why a gauge beats a tape measure for the job.
Drop-in or rocker-style: which is more accurate?
A drop-in gauge such as the Park Tool CC-3.2 rests its pins on the same side of two rollers, so its reading includes roller wear and roller slop as well as genuine pin elongation, and it tends to condemn a chain slightly early. Rocker and pivot designs like the Shimano TL-CN42, the Pedro's Chain Checker Plus II and the Rohloff Caliber 2 push the rollers to one side first, so they isolate pin wear and read a little later. Either is fine as long as you use the same tool consistently; problems come from switching between the two and reading the difference as sudden wear.
Do I need a chain checker or will callipers do?
You can measure 12 complete links, which should span exactly 12 inches, and replace the chain once it runs about 1/16in over — accurate, but fiddly on a fitted chain and hard to do repeatably. Callipers are the better buy if you also want to check rotors, pads and seatposts; a dedicated gauge is the better buy if the only question you ever ask is whether the chain has had it. Both sit under measurement tools.
What wears out on a used chain checker?
The measuring tips are the whole tool, and they are the part that gets dragged in and out of dirty chains hundreds of times. A worn tip is narrower than it was, so it drops further into the roller gap and reports wear the chain has not got — the test is to try it on a brand-new chain, where it should sit proud and read zero. On rocker-style tools check the pivot has no side-to-side slop and the spring still returns the arm, and on digital models check the display for a dead segment and the battery hatch for corrosion.
What is a used chain checker worth?
These are small, cheap new and cost almost nothing to post, so a used one only makes sense well under half of new — above that you are paying for someone else's worn tips. A shop-grade tool with unmarked tips is worth more than a basic gauge in poor condition. Buy new if you have no new chain to test it against, because an unverified checker gives you a number you cannot trust.