This magical bike tool saves cyclists money

Last week we wrote about the magic of the humble barrel adjuster. I asked if bike maintenance articles that provide big wins for cyclists, but are extremely accessible for beginners is something you’d like more of. The answer was overwhelmingly yes.

This week therefore, I want to share with you a £5 tool, that can save you £30 or more every year you use it.

That humble little £5 tool, is the Chain Wear Tool, which looks a little like this:

Park tool chain wear tool


What does this magical tool do?

Well, you see, every mile you pedal, every hill you climb, every car you overtake in the morning rush hour, slowly wears away at your bicycle chain.

Generally, you’ll need to replace the bicycle chain 1 to 3 times per year, depending on the riding you do.


If you don’t replace the chain, and you keep riding with a worn out chain, then you end up wearing out your cassette.

This grimey old thing:


Bummer dude – as a surfer would say upon seeing no waves today.

So how does one avoid this eventuality?

One must know when to replace ones chain. 


As the instructions in our ever wonderful Bike Doctor app (download it, support London Cyclist!) will tell you:

  1. Get your chain wear tool
  2. Drop the one end with a hook in to your chain
  3. If the other end marked 0.75, drops right through, then your chain is worn
  4. If the 1.0 end drops through, then you also need to replace your cassette – sad face

Chain wear tool

(In the picture above, it’s almost time to replace the chain)

You can normally replace your chain 2-3 times, before you also need to replace your cassette.

A chain replacement is about £10-£15. A cassette replacement is £30-£50. Depending on whether you do it yourself, or get a shop to help you.

Save your cassette – know when to replace your chain!

Before you die hard bike maintenance nuts jump in on the comments and say:

“Hey Andreas! You don’t even need a chain wear tool, you can just work it out yourself”.

It is 100% true my friend. If you want to save £5 and work it out yourself, here is how you do that. Personally, I prefer a chain wear tool which will instantly tell me if it’s time.

Want more bicycle maintenance goodness? Learn about the barrel adjuster:

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10 Responses to This magical bike tool saves cyclists money

  1. Nick 15/05/2014 at 1:33 pm #

    There’s a typo. It should say £10 not £5.

    • Andreas 15/05/2014 at 4:41 pm #

      You can find £5 options that will do the exact same thing – I just picked the Parktool one for reference.

  2. Mrs janet groves 15/05/2014 at 5:36 pm #

    Thanks andreas. I had read that I needed one of these: but didn’t understand how to use it . – or why. . -thanks again for your help.

  3. Phil 16/05/2014 at 6:08 am #

    I buy 3+ chains for a new cassette and rotate them monthly. This is because if you replace a chain at .75 mm as shown on the marker gauge, some wear will have already taken place on the cassette. So even though the cassette still has some life in it, the wear will shorten the life of the next chain.
    But the gauge mentioned in the article here, definitely makes the job easier.

    • Andrew Wilcox 16/05/2014 at 10:47 am #

      Good idea Phil.

      Excellent article Andreas

    • Jo 16/05/2014 at 12:55 pm #

      But for the cost of three chains on rotation is it easier and as cheap (using standard components at least) to run one chain and cassette completely into the ground and save the hassles and grime associated with swapping chains regularly?

  4. George 16/05/2014 at 11:46 am #

    But make sure you get the size you want. I have a Park tools gauge that measures 0.5 and 0.75 rather than 0.75 and 1.0mm as shown above. Who knows which is right? And the wonderful Jonathan, who runs the regular bike maintenance workshop for our local cycling group and who knows everything about common sense mechanics, scoffed when I turned up with a new chain to fit and told me I had months more wear in the old one (mind you, that was with a hub gear so there’s no chain line wear and the rear sprocket is cheaper to replace than a full cassette.)

  5. Paul 16/05/2014 at 12:23 pm #

    Does the same apply to single speeds and bikes with hub gears? I have no idea.

    • Antony 16/05/2014 at 1:25 pm #

      The tool can and should be used for any chain, single-speed or not. However since single-speeds obviously never change gear or experience cross-chaining, the chain and cog don’t wear as quickly as a geared bike. So if it’s set up right you probably won’t need to change the chain or cog as often.

  6. Andrew Priest (Aushiker) 16/05/2014 at 1:47 pm #

    Actually that particularly tool is not a very good one at all. You might find it informative to review the paper, Chain Measuring Tool.

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