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Chain Adjustment - When and Why

24881 Views 17 Replies 11 Participants Last post by  davy.j
The principal reason why drive chains fail is from excess tension caused by being installed too tight. Since the swingarm pivot is not concentric with the front sprocket, the chain length needs to accommodate the constantly changing distance between the front and rear sprocket as the rear suspension moves up and down. So the dimension on the swingarm sticker is intended to prevent you from installing the chain too tight. Looser is O.K.

You’ll use the sticker tightness measurement when you need to reassemble after changing sprockets or changing a tire on a bike with double-sided swingarms. Bikes with single-sided swingarms have eccentric adjusters, so no adjustment is required when changing a tire.

Once the chain adjusters are locked down there’s no reason to periodically readjust the chain. Chains get longer, not shorter, as they wear.

As the internal pins and bushings in a chain wear, the chain length of the affected segment gets longer, and when it exceeds 2 mm for a 16-link segment, the chain needs to be replaced. Chains don’t wear evenly, but even if they did, the overall increase in length of a chain needing replacement is less than 11 mm. Consequently, you don’t need any periodic adjustments to compensate for this small amount of wear for the life of the chain. You do, of course, need to periodically check 16-link segments of the chain for excessive wear and replace the chain if necessary.

You’ll need do a chain adjustment when the chain has been loosened to change a tire or sprocket. Also, a 3,000 mile or so tire change interval seems like a reasonable time to check for chain stretch. If you bring your bike to a dealer for a tire change, ask them ahead of time to write down the chain stretch amount for at least three segments of chain. This will put them on notice that you expect them to do it. It’s not often a dealer will actually do the check and a snapped chain is the consequence.
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I have always thought that a chain could wear/stretch beyond an acceptable amount which is when one gets too much backlash in the drive, but still have plenty of life in it once re-tensioned to recommended spec/play.

I always thought that if a chain gets too loose, it will create sprocket and worse, gear box damage from backlash. Indeed, for Ducati owners, a chain that might be too loose may jump off the front sprocket enough to damage the engine case.

I pay attention to how my bike takes up the slack/changes gears etc, and if I detect excessive backlash, I will adjust chain tension,as per tighest spot etc. back to spec tension/play, and usually find all is well again re shift quality/no excessive backlash in the drive. If I can't adjust the chain to where it does not get way too tight and then way to loose as it rotates on the sprockets, I change everything.

I always thought that a properly aligned chain with "locked in" adjusters, can still stretch/wear to where it's too loose/excessive backlash, *but still have plenty of life in it.* :)
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