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Chain Checkers Do No Good Just Sitting in Your Toolbox

I have not been regularly checking my bicycle chains for wear.  I have no excuse for not doing so.  I have the necessary tool for the job.  Two of them in fact.

Chain Checker

The purist will argue that a steel ruler or steel tape measure is the most accurate tool for measuring chain wear.  Using a ruler can however be error-prone because it is necessary to hold the ruler precisely and measure one end while making sure the other does not slip.  So tools like these ones have been created.  They are not as accurate as a properly-used ruler, but they are an easier and faster way to measure chain wear.

Chain wear is often referred to as chain stretch, but this is a misnomer.  The side plates of a chain do not deform under pedalling forces.  Rather it is wear to the pins, bushes and rollers that causes the distance between the pins to increase, thus giving the illusion of stretch.

This diagram shows A. pin/bushing wear, and C. bushing/roller wear.  B shows an unworn chain.  Note that roller wear does not affect pin spacing.

Illustration courtesy of par do.net at http://pardo.net/bike/pic/fail-004/000.html

Illustration courtesy of pardo.net at http://pardo.net/bike/pic/fail-004/000.html

In short, chain wear is indicated by an increase is the spacing between pins.  When I finally put my BBB chain checker to use it showed that the chain on  my titanium Alchemy bike had reached the point where it needed to be replaced.  What I didn’t know was when the chain had reached that point.  Had I been riding for too long on a worn chain, and perhaps damaged the drive train in the process?

Some of my Racun Cycling Gang had recommended Meng Thai Bicycle Centre for bike parts and service.  So I took the bike there to have a new chain installed.  Labor costs are still relatively low here as compared to the Netherlands, so I had less incentive to do it myself.  When I say low I mean a labor charge of  RM 30 / USD 9 to have a new chain installed and to get the bike serviced and tuned up.

My first ride with the new chain was up to Genting Sempah.  It quickly became obvious that I had waited too long to replace the chain.  The chain was skipping on one cog.  It didn’t matter which chain ring I was in.  The chain skipped on that one cog.

At first I couldn’t tell from looking at the cassette that there was anything wrong with it.

IMG_1663

A closer look revealed where the problem lay.

Cassette Wear

That shark-tooth profile on the fourth cog is not normal.,  The new chain rides too high up the ramp of the tooth and slips off.  The only solution was a new cassette.  I went with a SRAM PG 1070 cassette at RM 250 / USD 76 rather than replacing this SRAM OG 1090 cassette at RM 650 / USD 198.

The moral of this tale is to regularly check your chain for wear.  I now know, thanks to the late and great Sheldon Brown, that a chain that has just 1% of wear should be replaced.  Anything more than 1% chain wear and the sprockets are probably already damaged.

What is 1% of chain wear?  Ten links of a new chain are 25.4 cm long, measured from pin to pin.  If the last pin in link ten is just past 25.5 cm the chain needs to be replaced.  If the last pin is approaching 25.7 cm away then the most-used sprockets are already damaged.

I got 10,000 km / 6,214 mi out of the cassette.  I wonder how many more kilometers it would have lasted if I had replaced the chain as soon as it showed 1% wear.

I replaced the chain on the steel Alchemy a few days ago.  The cassette on that bike has 13,300 km / 8,265 mi on it so far.  Including 115 km / 71.5 mi with the new chain.

I caught that one in time.  No skips.

About alchemyrider

I left Malaysia in 2008 as a non-cyclist. I am back home now with two road bikes and all the paraphernalia that goes with being addicted to cycling.

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