Chain length

[meddyliol]

I am about ready to start putting my new front and rear derailleurs on along with a new chain and new twist grip shifters. I have looked at loads of youtube vids on how to do all of this but am still a little confused. Bolting on all of the bits isn't a problem it's things like, how to get the chain length correct, how to get the twist grip cables the correct length etc etc etc. I found a way of how to get the chain length right but cannot find it again.
I apologise for being a little thick but I obviously need to get this right even if it is a crap bike.

Thanks

Brian

 

[Yellow Saddle]

If you've looked at the videos, they would probably have dealt with wrap plus two links etc etc.
I can't better describe in text what a good video can do but I can give you some principles that they may not have dealt with and can lead to confusion. Only two things are important:

1) Understand what "link" means. A link is a two-part affair and comprises one inner and one outer section of chain. This section will be exactly one inch in length measured from given point to given point (note not overall from left to right).
2) When installed, the maximum angles the derailer cage forms wrt to the vertical should be observed. In other words, in the biggest-biggest combination of gears (big sprocket up front, big sprocket in the back), then the derailer cage should not bend more than 45 degrees forward to the front wheel. Conversely, when in the smallest smallest gear, the derailer cage should not quite reach the horizontal position.

Within those two parameters, the chain is perfect.

 

[meddyliol]

Thanks for your reply. Just looked at this Youtube video (

View: https://www.youtube.com/watch?v=Vg2SoOOrpE8&t=5s
). Method two seems to follow what you suggest in your para two. So, that's probably the way to go.

 

[bonsaibilly]

If you've looked at the videos, they would probably have dealt with wrap plus two links etc etc.
I can't better describe in text what a good video can do but I can give you some principles that they may not have dealt with and can lead to confusion. Only two things are important:

1) Understand what "link" means. A link is a two-part affair and comprises one inner and one outer section of chain. This section will be exactly one inch in length measured from given point to given point (note not overall from left to right).
2) When installed, the maximum angles the derailer cage forms wrt to the vertical should be observed. In other words, in the biggest-biggest combination of gears (big sprocket up front, big sprocket in the back), then the derailer cage should not bend more than 45 degrees forward to the front wheel. Conversely, when in the smallest smallest gear, the derailer cage should not quite reach the horizontal position.

Within those two parameters, the chain is perfect.

I just did my first ever chain replacement yesterday and the only observations I can make are: 1, that I had to count the number of links in the departing chain and then just cut the new one to the same. and 2, that the product packaging defines a link as half of what you described, ie it said "116L" which was the number of half-inch sections/the number of round bits where the links are made (minus 1).

3, I got very oily.

BB

 

[meddyliol]

I suppose using the old chain gives a rough guide but doesn't account for chain stretch. I have no idea how much a chain actually stretches though. A good point though.

 

[Yellow Saddle]

I suppose using the old chain gives a rough guide but doesn't account for chain stretch. I have no idea how much a chain actually stretches though. A good point though.

As BB says, if you count links, then wear lengthening doesn't matter.

 

[Yellow Saddle]

I just did my first ever chain replacement yesterday and the only observations I can make are: 1, that I had to count the number of links in the departing chain and then just cut the new one to the same. and 2, that the product packaging defines a link as half of what you described, ie it said "116L" which was the number of half-inch sections/the number of round bits where the links are made (minus 1).

3, I got very oily.

BB

That's why I defined "link" so that you don't get confused between what product packaging calls a link and what instructional videos and authoritative texts call a link. "Remove three links" is a flop if you get it wrong.

 

[MichaelW2]

Park tools repair website was three different methods of working out chain length.

 

[ColinJ]

As BB says, if you count links, then wear lengthening doesn't matter.

But then you are relying on the original chain being the correct number of links. If the first chain on the bike had been wrong then copying it would just perpetuate the error!

 

[wisdom]

I've only ever done it by counting the links.Of course that was assuming that the factory build put the correct length on (I would hope so).I've had these bikes from new.

 

[XC26]

Does your new rear derailleur have sufficient chain capacity to accommodate your particular combination of chainset and cassette/freewheel? By that I mean that when the chain is on the largest chainring and sprocket combination, the derailleur is not pulled ridiculously too far forward, but also when the chain is on the smallest chainring and sprocket combination, the chain is not left dangling with too much slack.

 

[meddyliol]

Does your new rear derailleur have sufficient chain capacity to accommodate your particular combination of chainset and cassette/freewheel? By that I mean that when the chain is on the largest chainring and sprocket combination, the derailleur is not pulled ridiculously too far forward, but also when the chain is on the smallest chainring and sprocket combination, the chain is not left dangling with too much slack.

I will try and fit it tomorrow and let you know

 

[mjr]

If your chain's too long, the derailleur won't be able to take up the slack in small-small and it'll sag and skip.

If the chain's too short, it won't fit over big-big, so it'll refuse to change into it, it'll skate or skip or autoshift or if you're really unlucky, something will break.

If neither of those happens, it's probably close enough