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Chain Adjustment - When and Why

24847 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'm going to add something else here... I find quite a difference between a cold adjustment and then hot when the bike has been run for a couple of hours and the swing arm, my alloy rear sprocket, and the engine have all expanded to their running size and this is magnified with larger than stock rear sprockets (for instance a 44t rear sprocket is about 30mm larger in diameter than a 38t one)
So I adjust for correct tension hot then re-check to see what it is cold and use that setting for normal checking and maintanance.
The other thing with alloy sprockets is they do wear a little faster than steel so the tension does change quite a bit in the first few weeks of use till the chain and sprocket have bedded together and the alloy teeth have work hardened with use and the chain lube has embedded itself in surface of the teeth

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