How to measure a bicycle chain

by Raymond Parker on April 30, 2011

in Technical

for new installations (on derailleur drive-trains) and to check for wear

Save the Sprockets!

Proper installation and regular inspection for chain wear will preserve your whole drive train and save you money.

New chain installation

There are several methods of determining chain length for derailleur-gear drive-trains, but none is more simple—or any more accurate—in my experience than the following:

  • Shift the front derailleur over the largest, outer chainring.
  • Wrap the chain around the largest cog on the cassette or freewheel (no need to thread through the rear derailleur).
  • Thread the chain through the front derailleur cage and over the big chainring.
  • Bring the ends of the chain together at the bottom of the wrap, alongside the chainstays, and pull tight.
  • Allow two extra links (two rivets, or 1 inch), beyond where the ends meet.
  • Cut the chain here.
  • Thread through the derailleurs and join.

Notes: If you intend to use a masterlink, install half the link on one end of the chain and measure to the other end. Leave inner, roller link plates and roller (see right).

Img description

Remove extra links

To join with chain tool, cut to outer pin/rivet link plate. Be careful to preserve rivet.

See the chain removal & installation guide for further info on chain breaking and use of master links.

Measuring your bicycle chain for wear

Perhaps no other bike maintenance regime will save your wallet more than keeping an eye on chain wear.

Left too long, a “stretched” chain will wear cog and chainring teeth to match. Beyond a certain point, you won’t be able to simply replace the chain as it won’t mesh with the reshaped pitch of the teeth.

The result of neglect can be an expensive lesson on modern, mega-speed drivetrains.

The simplest—and perhaps most accurate—method of wear measurement is accomplished with a steel measure:

  • Align an inch mark with the centre of a rivet and count 12 full links along the chain. Keep the chain taut.
  • On an unworn chain, a rivet will line up exactly with an inch mark—12 inches along.

As a rule (pun intended) the following measurements will indicate the health of the chain:

  • Rivet less than 1/16″ past the mark: ride on.
  • 1/16″ over the mark: replace the chain but cogs and rings are likely OK.
  • 1/8″ past the mark: Drivetrain is beyond help. Replace chain and sprockets.
  • A quick and easy way to measure can also be done with various “wear indicator” tools, like the Park CC-3.

    In my experience, such tools are calibrated conservatively. I often take a chain measured slightly beyond .75% on the CC-3 and move it to a bike with an older drivetrain. Re-cycling as it were.

    Img description

    Slightly worn chain: The 75% side of the Park tool fits tightly and twelfth rivet extends just beyond the 1-foot mark on ruler. Keep riding.

    Go to VeloGarage

    Listed Under Jobs: ,

    Listed Under Components: ,

Previous post:

Next post: