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How can I tell if a drive chain is knackered?

BTW. Now for the newbie bit. How do you tell if the chain is so worn that it needs replacing ? (side ways movement ?). usually it's when all the adjustment has been taken up i.e. the wheel is as far back as it will go.

Er, no! On my VFR, there's about 3 times as much room for adjustment as you need...

Grab hold of the chain on the rear sprocket, and see if it will lift up (i.e. will it come away from the sprocket at all). It shouldn't lift more than say 1mm.

Realistically, you can tell 3 ways:

tim
>  BTW.  Now for the newbie bit.  How do you tell if the chain is so worn that it
>  needs replacing ?  (side ways movement ?).
Well, for a start there's -

No adjustment left on adjusters, severe chain slap when riding, ticking noises from chain when the bike is wheeled backwards and/or forwards, grip the chain at the rear sprocket & try pulling it off the sprocket (grip at 3 0'clock position on LH drive, 9 oclock on RH); if the chain comes away from the sprocket at that point then bin it, excessive wear on sprockets, excessive sideways movement.

If sprockets are worn, replace both sprockets & chain. Fitting a new chain onto old sprockets is a waste of money, the shagged sprockets will relatively quickly shag the new chain. "Excessive" is a subjective measurement, I use an arc of 180 degrees as excessive, new chains exhibit an arc of about 45 degrees.

Another method is to was the chain in petrol and paraffin and get it like new. Let it dry and lay it out on a smooth floor on clean paper. Get hold of one end of the chain and pull the chain until the other end moves. Measure the chain length and note it. Next push the end of the chain until the other end moves. Measure the chain length. There should be no or very small difference in length with a new chain. Worn chians will show larger differences in the two lengths, the larger the difference, the more worn the chain. Unfortunately the point at which the wear is deemed excessive is subjective, I'd suggest that counting the number of links, and working out what the ideal length of the chain is calculating what the wear on each link is, I'd expect excessive to be about 10-20 though per link. Alternatively use a percentage measure, the difference between the lengths should not exceed 2% of the chain length, about 0.75" on an average chain. Again these are subjective values, some people may say 5 thou per link, others 25 thou, it all depends on your mechanical sympathy and the stress you can take worrying about your chain.

Don't forget though that chains wear unevenly.


This page last updated 17/09/02
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