Chain needs to be well oiled. With rider on the bike I go for 1/2" play on the final drive. Primary chain needs to be tighter, I would have thought 1/2" max. free play.

Have you checked sprocket alignment. Also is it possible for the rear wheel to move forward under load? e.g axle not torqued to recommended, stripped threads on the adjusters. You only need to check the bottom run. Free play equals total up and down movement at the tightest spot of the chain run.

Could be chain and sprockets are knackered.

Sounds to me like something has moved or...........

Did you remember to tighten all the gearbox nuts? Both adjuster nuts and the top bolt.

What about the wheel axle nuts?

The 'or' bit............if your chain has been previously dipped in one of those tins of hot oil/wax/goo then this tends to temporarily shorten a chain. How???

The hot lubricant gets into all the tiny spaces between each pin, roller and other bearing surfaces. Because it gets both sides of each pin, it effectively pushes each set of rollers towards each other and closes up all the corresponding links. The trouble is.....it only lasts for a few miles of riding. Then the goo all gets squished to the back side of each pin and the chain stretches again.

If this is the cause of your chain stretching, then it may be past its best. The solution....buy a new chain.

Check your primary chain tension - if there has been some movement of the gearbox (not uncommon) you may find the primary chain is now worryingly tight. I set the primary chain adjustment with my oily boot pressing down on the rear chain to keep that in tension whilst tightening up the assorted nuts. Then I adjust the rear chain. Caution- don't try this if you have a dodgy hip! A new chain may show some stretch fairly soon but a mature one should stay in adjustment for a good while.

Remember to check both the chain tensions at several different points. There can be quite a difference between the slackest and the tightest positions.

Previously Gordon Johnston wrote:

A new chain may show some stretch fairly soon but a mature one should stay in adjustment for a good while.

Chains don't stretch, they elongate through wear. A good quality chain on good sprockets will wear less when new than a 'mature' one.

Elongate.....now there's a posh alternative to stretching. Are we splitting hairs here or just trying to be controversial.

Science tells me that.......All metals expand when heated and/or subjected to a pulling force....and do the opposite when cooled or subjected to a crushing force. Unless they exceed Young's Modulus in which case they do not go back to their original form but remained expanded or stretched or lengthened etc.

Wear in the chain bushes causes elongation of the bearing surfaces which in turn allows the chain to lengthen or according to both Haynes and Haycroft.....'cause stretching'. A chain deprived of lubrication will heat up through internal friction which in turn will open up the tolerances. Therefore a bit more stretching will take place.

I'm not certain if there is enough horse power generated to physically stretch the side plates under full load. According to Young....yes!!!

The prisoner was found guilty and sent down for a long stretch ...........sorry! Elongation!!!

Just remember that chains don't wear evenly. Where the chain might be the correct tension in one place it might be tight or slackin another once the wearing process has started.

After making the adjustment, check with a load on the bike and then in several positions of the chain.

Previously phil_hannam wrote:

Elongate.....now there's a posh alternative to stretching. Are we splitting hairs here or just trying to be controversial.

Science tells me that.......All metals expand when heated and/or subjected to a pulling force....and do the opposite when cooled or subjected to a crushing force. Unless they exceed Young's Modulus in which case they do not go back to their original form but remained expanded or stretched or lengthened etc.

Wear in the chain bushes causes elongation of the bearing surfaces which in turn allows the chain to lengthen or according to both Haynes and Haycroft.....'cause stretching'. A chain deprived of lubrication will heat up through internal friction which in turn will open up the tolerances. Therefore a bit more stretching will take place.

I'm not certain if there is enough horse power generated to physically stretch the side plates under full load. According to Young....yes!!!

The prisoner was found guilty and sent down for a long stretch ...........sorry! Elongation!!!

One reason I like engineering as a subject is that there is no room for bullshit. Any sound argument can be backed up by proven theories. Communicating using correct terminology is essential.

Stretch implies a material subjected to a tensile load within it's elastic limit (Young's modulus) so when the load is removed the material returns to it's original state.

A chain which has lengthened (elongated), with no wear between bushes, has been loaded past the elastic limit and into the plastic limit and does not return to it's original length. Any chain which has exceeded the elastic limit will not be far from breaking under load as the materials tensile limit is already exceeded. The fact that chain breakages are rare, but lengthening is not, implies that wear between bushes and rollers takes place, causing lengthening of the assembly. So chain lengthening is due to wear, not stretching.

Very funny joke Phil. Busy time of year for you I imagine with the christmas crackers.

Readers, of this thread, will think that this lengthy discussion has possibly stretchedtoo far.Even elongated beyondits elastic or plastic limit, with no chance of it returning to something comprehensible.

On a much more festive note, which suitably goes with the original enquiry by Chris Rogers. Check out the following video on YouTube.

The United Kingdom Ukulele Orchestra Plays The Chain by Fleetwood Mac. Most people will know this tune from BBC TV Formula 1 Racing programmes. But not played in this non-elongated form.

http://www.youtube.com/watch?v=PRw3Bgg_9Uo