Chain stretch

Father Jack

wondering how much my chain has been stretched, gave it thorough clean too.



12" = 12 links or something?

andrew_s

measure the chain with it pulled tight.
the pins are 1/2 inch apart on a new chain.
Put the 1" mark of your tape level with the centre of a pin, then check where the 13" mark is. A used chain will have got a bit longer, so the centre of a pin will be just past the 13" mark.
A ruler gives a more reliable result than a chain checker. These include roller movement in what they measure, and as that varies between brands of chain as well as wear, the checkers generally err on the side of caution and will show a chain as being more worn than it actually is. It has been known for an unused chain to show as worn out.

If it's 1/8" past the 13" mark, the cassette will be worn enough that a new chain will slip if you stomp on the pedals. At this point you've got to change the cassette as well as put a new chain on. You can just leave the chain on and keep riding, but that will also wear the chainrings.

If it's less than 1/16" past, the cassette will be pretty much undamaged. You can put new chains on the same cassette repeatedly provided you keep on changing chains before 1/16" wear.

In between 1/16 and 1/8", the cassette will be worn enough that a new chain will wear a bit faster than normal until it's caught up with the state of wear of the cassette. The end result is that you'll need a new cassette after 3 or 4 chains.

On 9 speed, I've found that a chain can reach 1/8" stretch after as little as 1000 miles, and that if you just keep on riding you'll start getting transmission problems and have to change chain and cassette after about 7500 miles.
How fast a chain wears depends on riding conditions (wet/dry, mud, the local type of grit), what your chain cleaning regime is, how many speeds the chain is etc. In extreme cases a chain can reach 1/8" in a single ride (MTB).

What is best to do depends on the kit you buy. If you use an 11-34 10-speed cassette that cost £120, it's worth protecting it by changing chains early. On the other hand if you are using an 8-speed cassette that cost you £15, there's not much point in buying lots of £10 chains trying to keep it in good nick.

Father Jack

in metric please :-)

CarlosDSanchez

12" = 304.8mm

slowondefy2

Do bigger chain rings give noticeably slower chain wear? (or compact rings to faster chain wear?).

dilemna

Preferrably measure the chain on the bike under tension and before you clean it thus saving you all the hassle and wasted time of cleaning and lubing if it is too far gone. Measure the chain at numerous points not just one. I have found stretch can vary along the length of the chain. Common sense really. Use a chain wear tool eg Park which is far easier and more accurate than a tape measure which can slip slide and generally move around.

John.T

Use a chain wear tool eg Park which is far easier and more accurate than a tape measure which can slip slide and generally move around.

Not true. A ruler or steel tape takes play in the rollers out of the measurement. The tools don't and can show even a new chain as worn. The ruler only shows chain extension which is what causes cassette wear.

topdude

Not true. A ruler or steel tape takes play in the rollers out of the measurement. The tools don't and can show even a new chain as worn. The ruler only shows chain extension which is what causes cassette wear.

Spot on, a decent ruler with imperial measurements is far more accurate than a go / no-go tool.

Also it is no good thinking in metric as the chain has an Imperial half inch pitch.

surreyxc

"Not true. A ruler or steel tape takes play in the rollers out of the measurement. The tools don't and can show even a new chain as worn. The ruler only shows chain extension which is what causes cassette wear."

Is that true, I am in the office so can not verify. However my understanding is that the plates actually stretch little, it is the rollers and rivets which are subject to distortion/wear, and this is what the chain wear tool measures.

From the man himself Sheldon, may he rest in piece:

"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. "

surreyxc

'peace'

John.T

However my understanding is that the plates actually stretch little, it is the rollers and rivets which are subject to distortion/wear, and this is what the chain wear tool measures.

Quite right. The plates do not stretch. There are 2 places on a chain where wear takes place. Between the pins and the bushing, and between the rollers and the outer part of the bushing. The former causes the chain to 'stretch' which wears the cassette. The latter while making things a bit sloppy does not have any real affect on performance as it does not alter chain pitch. A ruler only measures pin / bushing wear but the tools measure both together thus giving a false reading as they push one roller in the oposite direction to which it operates.
By all means use one if you like to change your chain more often than you need to but I am not going to. They cost nearly as much as a chain anyway but I am sure we all have a ruler somewhere.

dilemna

John.T wrote:

However my understanding is that the plates actually stretch little, it is the rollers and rivets which are subject to distortion/wear, and this is what the chain wear tool measures.

Quite right. The plates do not stretch. There are 2 places on a chain where wear takes place. Between the pins and the bushing, and between the rollers and the outer part of the bushing. The former causes the chain to 'stretch' which wears the cassette. The latter while making things a bit sloppy does not have any real affect on performance as it does not alter chain pitch. A ruler only measures pin / bushing wear but the tools measure both together thus giving a false reading as they push one roller in the oposite direction to which it operates.
By all means use one if you like to change your chain more often than you need to but I am not going to. They cost nearly as much as a chain anyway but I am sure we all have a ruler somewhere.

Well you stick to your method using a tape measure and I'll stick with mine using the Park chain wear tool and I bet your bike will have a knackered cassette and chain rings before mine :roll: .

Cost of chain wear tool £8. Replacement costs for a chain £8 to £40, cassette £40-60, chain rings or crank £££££. How much does a decent tape measure or metal rule cost, £6 - £10?

.

dilemna

John.T wrote:

Use a chain wear tool eg Park which is far easier and more accurate than a tape measure which can slip slide and generally move around.

Not true. A ruler or steel tape takes play in the rollers out of the measurement. The tools don't and can show even a new chain as worn. The ruler only shows chain extension which is what causes cassette wear.

They do or they don't :? ? You contradict yourself here.

Errr ............. my chain wear tool doesn't show a replacement new chain to be worn :roll: .

dilemna

andrew_s wrote:

measure the chain with it pulled tight.
the pins are 1/2 inch apart on a new chain.
Put the 1" mark of your tape level with the centre of a pin, then check where the 13" mark is. A used chain will have got a bit longer, so the centre of a pin will be just past the 13" mark.
A ruler gives a more reliable result than a chain checker. These include roller movement in what they measure, and as that varies between brands of chain as well as wear, the checkers generally err on the side of caution and will show a chain as being more worn than it actually is. It has been known for an unused chain to show as worn out.

Evidence. When was this? Make of chain wear tool and that of chain please. Was the chain wear tool being used correctly?

ooermissus

A long explanation for why...

Commercial tools are conservative and never report a chain as good when it is actually worn. They may, however, report a good chain as worn, leading to increased chain costs.

http://pardo.net/bike/pic/fail-004/000.html

John.T

Well dilemna. You do it your way. I get around 10000 miles and 3 chains per cassette on my summer bike and 1 cassette and 2 chains per 2 winters, about 6000 miles, on the winter one so I am not complaining. I am also not going to argue as your mind is obviously set.

topdude

Well done "ooermissus" excellent article on chain wear.
That about puts it to bed then, learn how to use a ruler correctly

http://pardo.net/bike/pic/fail-004/000.html

Oh and don't use WD40 as a chain lube

balthazar

topdude wrote:

Well done "ooermissus" excellent article on chain wear.
That about puts it to bed then, learn how to use a ruler correctly

http://pardo.net/bike/pic/fail-004/000.html

It was put to bed the last time that (impressive and thorough) analysis was cited. The argument will be back around again. I give it a week.

careful

I dont think the article does "put it to bed". As the articles states "roller wear is added to the measurement, even though it does not affect proper chain operation". Most chain checkers do not measure roller wear, or to be strictly correct, they measure wear on one side of each of the two rollers that they touch and do not measure wear in any of the rollers in between. It is true to say that the wear inside one of these rollers does not contribute to alteration of the chain's pitch and should therefore not ideally be measured. To get things in perspective, the inaccuracy amounts to the wear inside one side of one roller, irrespective of the length of chain measured. This adds to the measured wear from one side of every pin and one side of every bushing. Often the checker will span a dozen or more pins (cumulatively). It is therfore correctly measuring 24 valid points of wear plus one that is not valid.
Keep using your chain checkers guys, the inaccuracy amounts to probably 1/24 of the wear measured and could be ignored.

dennisn

You can see the difference if you lay your used chain next to a new one. Make sure both are pulled taut.

John.T

It is therfore correctly measuring 24 valid points of wear plus one that is not valid.
Keep using your chain checkers guys, the inaccuracy amounts to probably 1/24 of the wear measured

No. All roller wear is invalid when measuring 'stretch'. The guages include 2 sets of rollers so the potential error is 1/12th. But as even new chains have more play in the rollers this error is considerably more.
This does not alter the fact that careful measurement with a ruler is the most acurate and the final point for me as a Yorkshire Tyke. The ruler is cheaper and can be used for other tasks too.

dennisn

Probably the best way to measure center to center of pins is to measure from the outside edge of one to the same outside edge of another, 12 inches apart. This method is a bit easier as it gives you a definate edge to measure to. Taut, please remember taut.

John.T

Taut, please remember taut.

I always work with 10" (and a ruler with 1/10") of chain. It is easier to measure while your right knee is pushing the pedal.

Twostage

Chain stretch story :-

Thought I would replace the chain on my old MTB before doing the C2C as I couldn't remember the last time it was changed. Couldn't understand how when I held the old and new up next to each other the links definitely went out of sync but by the end the links lined up. Realised it had stretched a full link (1/2 inch). I knew that this amount of stretch could wear the cassette so I took it out on a test. Amazingly everything seemed OK.

200 yards away from the start at Whitehaven the chain started jumping and I was forced to do the route sticking to the first 5 gears and couldn't stand on the pedals without it jumping.

I had considered taking the old chain just in case but was determined to travel light so left it.

Plenty of lessons there I think.
:? :?