Chain Tension

[SERGE]

Girls and Guys,

After my bike's first 300 miles I felt like something was loose. Every time I "rolled on/off" I felt a "klunck!!!". Apparently it was the chain; it was loose.

They adjusted it but the problem did not go away. I took it back and the guy said he would tension it a bit more ... and IT WORKED!!!

My question is, what can an overtensioned chain do to the bike? He said it was a "hair" short of "to tight", but that I should be OK.

Thanks,

[rmcelroy]

i belive if it is too tight, it would have a tendancy to break easier? maybe? i really dont know... in fact, consider that a question... is that the right answer?

or maybe having it too tight will just wear the chain out faster because of the obvious fact that there is more tension on it... again, another guess...

am i correct?

[LayinLo]

It'll just stretch faster.

[jtg999]

^^^^^^^^he is right there^^^^^^^^^

tightning the chain to tight will strtch it or even snap it.

I got told by my local bike shop dealer that the chain should move 2 inches both directions, don't no if that is right or not.

josh.

[Clint]

Chains do not "stretch". They wear at all the contact points and become longer between each link. SERGE, tell us about your bike (and get a signature up). If it's an older chain, it may already be climbing the sprocket. That happens when the links get spaced too far for the tooth spacing. It's a warning of impending disaster, and you need to replace the chain and sprockets immediately.

If it's not old, and hasn't been abused, then you just need to tension it ACCORDING TO THE MANUAL. If you don't have one, get one. All bikes are different, and slack measurements and technique can vary also. Typically, you should be able to move the chain up and down about one inch at the loosest poing. Read the manual!

Let's take it easy on the quick, oversimplified answers to technical problems, guys.

[themeatmanlandry]

A too-tight chain is extremely bad for the countershaft. That's the main shaft coming off the transmission. If that gets bent, you're in for a world of hurt ($$$$).

I run my chain at the loose end of the recommend specification for that very reason.

[advr4]

your chain should have between 0.8"-1.2" (20-30mm) of slack, not 2" (50mm).

[FIVEINCH]

Originally Posted by RowdyRed94

Chains do not "stretch". They wear at all the contact points and become longer between each link...

Let's take it easy on the quick, oversimplified answers to technical problems, guys.

From: http://www.m-w.com/cgi-bin/dictionary

Pronunciation: 'strech
Function: verb
Etymology: Middle English strecchen, from Old English streccan; akin to Old High German strecchan to stretch, Old English stræc firm, severe
transitive senses
1 : to extend (as one's limbs or body) in a reclining position
2 : to reach out : EXTEND <stretched out her arms>
3 : to extend in length <stretched his neck to see what was going on>
4 : to fell with or as if with a blow
5 : to cause the limbs of (a person) to be pulled especially in torture
6 : to draw up (one's body) from a cramped, stooping, or relaxed position
7 : to pull taut <canvas stretched on a frame>
8 a : to enlarge or distend especially by force b : to extend or expand as if by physical force <stretch one's mind with a good book> c : STRAIN <stretched his already thin patience>
9 : to cause to reach or continue (as from one point to another or across a space) <stretch a wire between two posts>
10 a : to amplify or enlarge beyond natural or proper limits <the rules can be stretched this once> b : to expand (as by improvisation) to fulfill a larger function <stretching a dollar>
11 : to extend (a hit) to an extra base usually by fast or daring running <stretch a single into a double>
intransitive senses
1 a : to become extended in length or breadth or both : SPREAD <broad plains stretching to the sea> b : to extend over a continuous period
2 : to become extended without breaking
3 a : to extend one's body or limbs b : to lie down at full length
- stretch·abil·i·ty /"stre-ch&-'bi-l&-tE/ noun
- stretch·able /'stre-ch&-b&l/ adjective
- stretchy /-chE/ adjective
- stretch a point : to go beyond what is strictly warranted in making a claim or concession
- stretch one's legs 1 : to extend the legs 2 : to take a walk in order to relieve stiffness caused by prolonged sitting

Umm... no.

I'm pretty sure chains can be stretched. Now, shall we go into the elasticity of a sportbike chain which would be a characteristic imposed upon the chain by use of rubber-compound seals and tensile properties of the metal used?

[wgd9891]

you tell 'em five inch

[themeatmanlandry]

So . . . when you need a crankshaft bearing . . . do you actually call the shop and say your old one stretched?

I doubt it.

It wore out, just like the chain rollers. Now if the links were made of elastic . . .

[bat4255]

Some play is required to allow for the tightening effect that happens when there is weight applied. Check the tension when there is no weight on it, then check it with you sitting on it. You should notice it being less slack. Now imagine going hard in a corner, or riding 2-up, or going over a sharp rise in the road. The chain might look sloppy with no one sitting on it, but it will snug up when your driving it. If it's set with no one on it, and it's a bit snug, guess what. It will maybe snap, or at the very least, interfere with the operation of the rear suspension when it's loaded. As stated earlier, check the manual for the proper procedure, and specs.

[Clint]

Originally Posted by FIVEINCH

I'm pretty sure chains can be stretched. Now, shall we go into the elasticity of a sportbike chain which would be a characteristic imposed upon the chain by use of rubber-compound seals and tensile properties of the metal used?

You're so far off regarding the seals (they don't carry any load, therefore they don't affect chain length) that I won't even get into the steel's characteristics. Landry's right. If you want to make this a team debate, complete with your cheering section, let me know. I'm in.

[Phease]

PHP Code:

If you want to make this a team debate, complete with your cheering section, let me know. I'm in. 


Sweet! Break out the popcorn.

Now remember no gouging, biting or punches below the belt, i want this to be a fair debate, now go to your corners.

[inspiron]

Just to add some oil to the fire ...

Chains are made of metal (obviously), with some o- or x-rings (a rubber-compound, I believe) ensuring that there is always grease between the pins and the bushings. However, metal can and will stretch when it is put under pressure.

If you take a new chain and compare it to one that's been on a bike for 5000 miles, you should notice that the used chain is somewhat longer.

I believe that the metal stretches - that's why you need to move the rear tire farther back to tension the chain, and you need to do this several times over the life of the chain. If the metal never stretched, it wouldn't suffer from metal fatigue, and wouldn't break.

Just my $0.02.

[themeatmanlandry]

I'm not sure those chains are made of the type of metal that stretches. They're steel . . . not copper. I'm pretty sure they hardened steel. Any actual 'stretching' would most likely be immeasurable with a simple ruler.

[Clint]

Exactly, Landry. Inspiron, I'm surprised at you. I even explained the lengthening process in an earlier post, and you still fell to the ignorant rumors. Tsk, tsk.

Of course metal stretches, but our chains aren't subjected to the 10's of thousands of pounds it would take to make that happen, nor are our sprockets up to the task. It's link wear, plain and simple. Take .5mm of wear times, what, 150 links?, and you've got 7.5 cm of "stretch". Isn't it obvious?

Lube those suckers!

[FIVEINCH]

So the chain doesn't stretch?





I'll take the hit on the seals. I'll also stand by the metal changing shape.



Oh, and I'll agree with the additive spacing created by the links wearing (such as old bearing). I was just saving that one for a moment such as now. Unfortunately, y'all beat me to it.

[FIVEINCH]

Um, if link wear is to blame for the additive spacing requiring the rear wheel to be adjusted rearward to compensate... why? What are the links made of? Are the links separate from the chain?



Tens of thousands of pounds? Maybe for an effect of a difference readily visible to the human eye. I counter with: repetitive, varying, pressures applied to each link by the sprockets paired with heat (absorbed, and generated).

If anyone gets their feelings hurt, just roger up. I won't know unless you tell me. Right now I'm just having fun while trying to learn something.

[Clint]

The links ARE the chain, along with the pins. There should be damn little heat in a properly lubed chain. Whatchoo talkin' 'bout, Willis?

Chain "Stretch"

Cyclists often speak of chain "stretch", as if the side plates of an old chain were pulled out of shape by the repeated stresses of pedaling. This is not actually how chains elongate. The major cause of chain "stretch" is wearing away of the metal where the rivet rotates inside of the bushing (or the "bushing" part of the inside plate) as the chain links flex and straighten as the chain goes onto and off of the sprockets. If you take apart an old, worn out chain, you can easily see the little notches worn into the sides of the rivets by the inside edges of the bushings.

http://www.sheldonbrown.com/chains.html

At the outset the term "chain stretch" is misleading and wrong. Chains do not stretch, in the dictionary sense, by elongating the metal through tension. They lengthen because their hinge pins and sleeves wear.

http://www.slowtwitch.com/mainheadin...nce/chain.html

...

Usually, when the chain is worn out so are the front and rear sprockets. This is because a chain does not "stretch" as it wears. It becomes elongated due to wear in the joints. This changes the pitch, which in turn wears out the sprockets.

http://www.dansmc.com/rearchain.htm

Chains don't stretch in the same way elastic bands do - they get longer because the metal in the links gradually wear away and makes the overall length of the chain increase. As the chain stretches, the amount of free play increases and you eventually have to move your rear wheel back a bit to take up the slack.

http://www.nobugs.org/bike/chain.html

Does a chain really "stretch"?
The term "stretch" is misleading. A chain will elongate when the pins and bushings wear down. This is due to poor lubrication, under sizing and overloading of the chain. As the components thin, the space between the pins and bushings increase, thus making the chain longer than originally.

http://tsubaki.nl/products/faq.html

[FIVEINCH]

Wow. There must have some MAJOR assumption of ignorance going on here. Not once did I hint to, elude to, or assume that the side links would change shape. Dude... c'mon. That's the heaviest and thickest piece of metal per link. The rollers and pins are the weak points to each link of these chains. In an extreme case of wear, you will find the holes of the side links have signs of wear, but by then the rollers and pins have already given way.

Wow. I guess if you really want to lead someone into a debate, just play dumb.

Sorry guys. I had assumed that, at the very least by observation of their own machines, everyone present knew the side links shouldn't change shape... elongate.

I stand by my posting of the definition of 'stretch' and how our chains fit into it. Mr. Jobst Brandt's literal interpretation of a defintion is a little inadequate, and nicely fits into his article... for some odd reason...

Go ahead and grab a thesaurus... anyone... and look up 'elongate'. I was just wondering what another word would be for that. I love to expand my vocabulary whenever possible. Since I don't go to school and study very much these days, I'm a little rusty!