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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 worry that your statement, "Once the chain adjusters are locked down there’s no reason to periodically readjust the chain. " could be misinterpreted.

Some people may take this to mean that once your chain is OK, there's no need to check it, even though you didn't actually say as much.

Additionally, may take what you posted as saying a slack chain won't present a problem as long as the wear limits are not exceeded. I just read a post about a guy who crashed when his too-slack chain jumped off and locked the rear wheel; thank goodness at low speed.

It is important to check the chain tension often. It doesn't matter how it got to be OK, if it's OK then it's OK. Likewise, it matters not how it might get too slack or too tight. If it's out of adjustment for ANY reason, it's definitely NOT OK. Believing that once it's OK, it will be OK for a long time could cause problems. Again, this isn't what you said, but your post could be misread.

In other words, even though my chain checks OK, knowing that it is highly unlikely to go out of specs once it's locked down is no excuse to ignore my chain tension, especially since it's so easy to check.

On my Monster 696, when the chain is properly adjusted (caution the English translation of the shop manual is incorrect but the Italian and Spanish versions are OK) I can just make it hit the lower rub block by pressing up hard with two fingers. Once you have a feel for that, it's easy to do a quick and dirty check without measuring. I grab a piece of paper (to keep my fingers clean) and quickly check my chain tension every time I refuel.
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Different makes and models have different ways to measure chain tension. I happen to believe that following the manufacturers recommendation is the way to go, but others think the factory engineers are stupid and prefer to "eyeball" their chain tension. Suit yourself.

Your bike may require measuring the difference between pushing up and pulling down on the chain. Many bikes specify this procedure. But my Monster 696 uses a different and, I think, a much easier and more accurate method.

Unfortunately, for the Monster 696 the English translation of the procedure is wrong, or incomplete to be more precise. You're supposed to put the bike on the side stand (not a paddock stand) and measure the distance from the bottom of the swing arm to the center of one of the pins. It should be 47mm. The English translation says to pull down on the chain to make this measurement. What it fails to say (and which the Italian version says) is to pull down and then RELEASE the chain before you make the measurement; BIG difference. Of course, if you don't have a Monster 696, this procedure, or at least the 47mm specification, is likely to be wrong.
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No one implied that factory engineers are stupid, though there are a lot of them (stupid) just like in any other profession. They have to work through restrictions, limitations and compromises.

What I cannot understand is the stupidity of people to condemn others just for expressing their opinion (right or wrong).

Keep in mind that ''Observation is the mother of science and repetition the mother of knowledge''.

But above all keeping an ''OPEN MIND'' is the most important part in life.
Steady there ................ In fact there are PLENTY of folks who believe that factory engineers are stupid, just take a look around the Internet.

But I don't think you can find an example where I said that YOU claim engineers are stupid or evidence that I condemned anyone, especially you, for simply expressing their opinion. In fact, I didn't even read your post until after you indicated that you were upset at my attempt to answer a question from someone seeking recommendations about chain tension.

I was responding to someone else and I simply pointed out a couple of ways people go about setting their chain tension and recommended to the OP, "Suit yourself". If you took that to be a personal attack, I fear you have misinterpreted my post and your vitriol is misdirected.

As far as I'm concerned, you can set your chain to any specification you wish using any method you like. As I said before, suit yourself.

Furthermore, if you want to convince anyone that your method is superior, feel free. After all, this forum is for the free exchange of ideas and opinions, right?

However, my advice to people who have NOT developed a method which they think is an improvement over the factory recommendation remains the same; follow the factory recommended procedure but be sure you know what that procedure is.
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Would you mind telling me whom were you referring to?
You are still passing judgement and advice (sic), .. snip ..........
And a "(sic)" back at ya'.

Let me give you some advice. If you feel like mocking someone when it comes to the subtle nuances of the English language, I advise you to first understand the difference between the words advice and advise before you offer your advice.

An Internet "gotcha'" looses much of it's sting when it reveals a lack of understanding of the matter at hand, wouldn't you agree?

I will continue to advise folks who want to adjust their chain properly to follow the advice given by the factory. If you consider that advice arrogant, I guess you'll just have to live with it.
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