How can I check chain wear and chain strength?

neil on big trike

Neil helped to set up Common Wheel over 10 years ago. Common Wheel exists to provide meaningful activity for people with mental illness by collecting, rebuilding and selling old bicycles. Neil has done a few tours in Scotland and built up dozens of bikes for touring.

Neil, from the bike workshop Common Wheel in Glasgow, Scotland, answers a question about chain wear.

The Question: “Are certain bike chains are stronger than others and therefore better for fully-loaded touring?

I have had chains stretch quite a bit and then wear out the teeth on the rings prematurely. So I was wondering if certain chains stretch less? And how do you gauge when it is time to change the chain? Is there a rule of thumb in terms of distance travelled?”

The Answer: “Chains wear, and it looks like stretch. This happens. You can delay the wear by oiling the chain lightly when it needs it, using mudguards, which keeps most dirt off the chain and not pedaling standing up.

Some chains are better than others. My favourite is the SRAM PC68. The Rohloff chains have a good reputation. The wider chains for 6 to 8 speed last longer than 9 and 10 speed, and if you are touring you don’t need such close gears anyway.

Chain wear is measured in the workshop by a special tool, but in the field you need an imperial ruler. Each rivet on a new chain is 1/2 inch apart, so it will line up with the marks on the ruler.

A worn chain will see the rivets overtaking the marks. If 24 links measure more than 12 1/8″, then replacement is due. At this point a new chain might work with old sprockets, but mostly chains are worn a lot more than this before the bike makes it to a workshop, so usual practice is to replace the sprockets at the same time, and possibly the chainrings.

The quick way is to change onto the big chainring, the try to pull the chain away from it. If there is a gap big enough to stick a pencil through, then the chain is worn.

There are so many factors affecting chain wear it’s not possible to give a mileage after which it should be replaced. Inspect every 1000 miles.” – Neil of Common Wheel

Thanks to Neil for answering the question. Get in touch to submit a question of your own to Ask A Mechanic.