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Chain stretch

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Arfdog
Crazy Courier



Joined: 17 Aug 2006
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PostPosted: 13:16 - 07 Nov 2006    Post subject: Chain stretch Reply with quote
Hi guys,

I cannot understand it. I find my chain has about 4 cm or more of play, of which 2 cm is TOTALLY free (slack) play, every 3 weeks or so. I tighten it JUST enough so that the slack is taken out of it, and then it's got about 2 cm of play. Not free flopping about slack play, but play under very slight tension.

Trouble is, I've done this 4 or 5 times already! my chain seems to be stretching at one hell of a rate... I still have about 15% usable space before I reach the end of my tensioning adjusters...

What you think? New chain? Or how can I check the problem is not with bearing on engine side of driving sprocket?

Cheers me dears
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Kickstart
The Oracle



Joined: 04 Feb 2002
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PostPosted: 13:19 - 07 Nov 2006    Post subject: Reply with quote
Hi

How well is the chain lubed? Is the rear wheel in line? Are you setting the chain tension to the recommended amount of slack?

Chains do wear out, and old sprockets wear them out even quicker (one reason why chain wear accelerates with age).

What bike is it?

All the best

Keith
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Arfdog
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Joined: 17 Aug 2006
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PostPosted: 13:28 - 07 Nov 2006    Post subject: Reply with quote
Hi Kick,

It's an ancient yamaha RXS100. I've lubed the train only twice (about once every 6 weeks). Prolly not enough.

I keep the tensioners on either side of rear wheel in line with each other, so the wheel must be pretty straight. When I set the chain, I set to manufacturers guidelines (2cm play). The sprocket looks like its in pretty good condition....
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Kickstart
The Oracle



Joined: 04 Feb 2002
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PostPosted: 13:31 - 07 Nov 2006    Post subject: Reply with quote
Hi

Suspect it is a small chain on that (420?). Likely to stretch rapidly. Check the front sprocket (just in case someone ignored that when they fitted the chain.

However you do need to lube your chain more often. That is likely to be the main culprit. With wet weather you could easily need to lube it a couple of times a week.

All the best

Keith
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0ddball
World Chat Champion



Joined: 15 Jul 2005
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PostPosted: 13:44 - 07 Nov 2006    Post subject: Reply with quote
Just sounds like a chain on it's last legs. Mine stretched so much it needed adjustin on a daily basis for about 2 weeks before it snapped.
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Trixie
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Joined: 27 Jul 2005
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PostPosted: 13:58 - 07 Nov 2006    Post subject: Reply with quote
Arfdog wrote:
I keep the tensioners on either side of rear wheel in line with each other, so the wheel must be pretty straight. When I set the chain, I set to manufacturers guidelines (2cm play). The sprocket looks like its in pretty good condition....


When you say about the tensioners either side of the rear wheel in line with each other, do you mean the adjustment marks on the swingarm? If so, it's possible your wheels are out of alignment, as these marks are very rarely accurate - don't use these to line everything up!
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Arfdog
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Joined: 17 Aug 2006
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PostPosted: 15:21 - 07 Nov 2006    Post subject: Reply with quote
Think I'll get a new chain (and lube it regularly).

yep I mean those adjustment marks..

Could you advise on a more accurate method please, Trix?
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Kickstart
The Oracle



Joined: 04 Feb 2002
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PostPosted: 15:23 - 07 Nov 2006    Post subject: Reply with quote
Hi

If you are replacing the chain then replace the sprockets as well.

Once you get the wheel in line (use a long straight bar against the rear wheel and check how close it comes the the fron wheel, repeat on the other side and compare), just adjust the chain the same number of turns / partial turns on the adjuster nuts on each side.

All the best

Keith
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Trixie
World Chat Champion



Joined: 27 Jul 2005
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PostPosted: 15:33 - 07 Nov 2006    Post subject: Reply with quote
Arfdog wrote:
Think I'll get a new chain (and lube it regularly).

yep I mean those adjustment marks..

Could you advise on a more accurate method please, Trix?


Pretty much what Kickstart says. Make sure the wheel is in alignment, then when you adjust the chain, make sure you turn the nut the same amount on each side; I normally use either a quarter or half a turn at a time. Thumbs Up
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Finglonga
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Joined: 27 Jul 2004
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PostPosted: 19:40 - 07 Nov 2006    Post subject: Reply with quote
2cm doesn't sound like enough slack, I would imagine its getting tight when the suspension is compressed. Just sounds like it would need at least double that.

Are you checking the tension on its tightest spot?
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Pete.
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Joined: 22 Aug 2006
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PostPosted: 20:16 - 07 Nov 2006    Post subject: Reply with quote
Check your wheel alignment with a straight-edge about 4 inces off the floor. It should touch at four points - front and rear of the front tyre and front and rear of the rear tyre. If it doesn't, you need to adjust it until it does. You can use string, or something like a long timber batten but make sure you sight along it before you do to be sure it's perfectly straight.

Another way is to use a tape measure and measure both sides from the swingarm pivot to the axle.
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Arfdog
Crazy Courier



Joined: 17 Aug 2006
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PostPosted: 08:22 - 08 Nov 2006    Post subject: Reply with quote
Finglonga wrote:
2cm doesn't sound like enough slack, I would imagine its getting tight when the suspension is compressed. Just sounds like it would need at least double that.

Are you checking the tension on its tightest spot?


Well, I've tried to sit on the bike and check the play then, but it seems to not change at all. I've also revolved the wheel to try find if the chain is tighter on some stretches, but it ain't.

When it comes to play, I am uncertain whether PLAY means SLACK, or if it means the amount you can move the chain up and down with your fingertips, whilst there is no slack.

So, if I tighten chain up as much as I can, I cannot budge the chain at all. It is taut, NO PLAY, certainly NO SLACK. I loosen it a bit, so that while it is still taught, I can move it up and down a little. This to me is PLAY. I loosen the chain further, which increases the PLAY, and I find when the play is about an inch, this is the point where SLACK begins to appear - the chain has no tension on it at rest, and can 'flop about. This is where I normally adjust the chain to, to the point where there is the tiniest amount of slack. Under this setting, about 0.5 cm movement up or down on the lower stretch of chain is enough to remove the slack, and a further cm or so brings it to the end of play, to the pint where it can no longer be moved. So the total range of movement would be 3cm top to bottom, of which 1 cm would be slack zone.

Now, maybe I am reading the specs wrong and actually need 2 cm of SLACK, but that makes the chain pretty loose! When it has that much slack I can actually feel a bump when I blip the accelerator. I would have thought slack in a transmission system would be very bad for the driving sprockets and gearbox bearings if it means NO LOAD for a tenth of a second before hitting to FULL LOAD, everytime you accelerate..

I bet no-one has posted such a long post about tensioning a chain before! Confused
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feef
Energiser Bunny



Joined: 11 Feb 2002
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PostPosted: 08:48 - 08 Nov 2006    Post subject: Re: Chain stretch Reply with quote
Arfdog wrote:
Hi guys,

I cannot understand it. I find my chain has about 4 cm or more of play, of which 2 cm is TOTALLY free (slack) play, every 3 weeks or so. I tighten it JUST enough so that the slack is taken out of it, and then it's got about 2 cm of play. Not free flopping about slack play, but play under very slight tension.


Sounds to me like your chain is actually too tight..

As soon as the suspension moves, it's going to start stretching that chain.

a
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Walloper
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Joined: 24 Feb 2005
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PostPosted: 13:23 - 08 Nov 2006    Post subject: Reply with quote
Measure 'Stretch' over several Link/Bushing Assemblies.
The OEM will provide a spec.
Usually five. This is the 'PITCH'
This adds up much more 'measurable' wear and determines if chain is reusable.
Also I (have to say it) Check that the adjustment isn't just backing off cause the axle nuts arn't tightening properly.
I don't think the chain would stretch and stretch and stretch. It might only do that once then snap.....

I had one of those silly light weight sprocket on a bike and the chain wore out within weeks of eating the hardened sprocket teeth.
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