measuring chain wear

[ozboz]

Hiya, i bought a vernier calliper a few weeks ago, so I am after using it to measure for chain wear, anybody know the specific readings I should look at for good to worn and over , metric or imperial over how many links, Cheers

 

[Yellow Saddle]

Pack away the vernier. It isn't much use when measuring chains. You want to measure the longest possible piece of chain so that you reduce the measuring error. On most bikes, that's 12 inches and taken on the bottom run of the chain with the chain on the big ring.

Find an imperial ruler that starts at the end - a steel rule or such - and goes beyond 12 inches. Good luck with that. A Parktool spoke rule works great. Now measure 12 links. No need to count. They are one inch apart so the end point for 12 links will be at the 12 inch mark. If it is exactly 112 inches, your chain is still in the packet. If it is slightly longer than 12 inches, you've been using it. If it measures 12 and 1 1/16th of an inch it has elongated by 0.5% and is at the end of the limit where it starts to eat cassettes. If it measures 12 1/8th, then it has had the cassette for breakfast already. Anything under 12 1/16th and you have a bit to go.

 

[Racing roadkill]

Cut out the guess work.

https://www.halfords.com/cycling/bike-maintenance/bike-tools/bikehut-chain-wear-checker
If it fits in between the links on the short side, your chain is on it’s way out, if it fits on the long side, it’s time for a new chain.

 

[andrew_s]

Using a ruler gives the definitive wear measurement.

The trouble with checkers like the bikehut one is that they measure between a roller pushed one way at one end, and a roller pushed the other way at the other end, incorporating roller movement into the measurement. Roller movement isn't a standard amount to start with, and increases as the inside of the roller wears (which doesn't affect the mesh of the chain with sprocket teeth).
If you use a brand of chain other than the one the checker was calibrated with, the check can be wrong (usually on the pessimistic side). It's not unknown for an unused chain to show as being in need of replacement using such a checker.

If you want to use a vernier, measure between rollers in the same way as a checker, but subtract a 1" measurement from a 5" measurement, thus giving the length of 4" of chain without including roller movement (4" = 101.6 mm, with 1 mm over that being 1% wear).
It saves on arithmetic if you've got a digital vernier, which can be set to zero on the 1" measurement.

 

[slowmotion]

£1.99 from Screwfix. I have no idea how accurate they are. If you really want to push the boat out, they do a half metre one for £3.99 or something.
https://www.screwfix.com/p/magnusson-ruler-305mm/5850v#product_additional_details_container

 

[ColinJ]

Find an imperial ruler that starts at the end - a steel rule or such - and goes beyond 12 inches. Good luck with that.

I found one twice that length on eBay and it was a bargain price.

Obviously though, the price wasn't high enough for the supplier to be able to afford to wrap it properly so it came just wrapped in brown paper and with a 20 degree bend in the middle!

I managed to get it almost perfectly straight but it was annoying that they hadn't bothered to enclose it in stiff cardboard.