Originally Posted by
stephr1
Seems to me that there might be more than .5% visual error in trying to use a ruler (even a steel one). Movement, visual angle, etc. would affect the reading. How do you do it and still ensure accuracy?
I have a caliper that can give me fairly accurate readings but even that can be problematic (like how to get 2 appropriately relative points to measure....like the same position on the 2 links used for measurement).
That's why yo measure over 10 or 12 links, minimizes error. with a chain checker you also rely on perfect machining and any error will be applied to just 1 or 2 links.
Get the Pedro's or Shimano checker if convenience is important, or the steel ruler if you can live with measuring. Sure, you may end up replacing at 0.45% or 0.55%, but that is OK. the 0.5% rule is not a hard rule and with regular cassettes and chains the cost shifts a bit forth and back between chain and cassette.
Those other chaincheckers are not accurate by design, so you may as well read tea leaves.
i also stretch the chain when measuring. Put the rearwheel down and push the crank to tension the chain. That way you get real world length under load.