big big chain sizing method dilemma

[Brenton Eastman]

Hi all,

Rear: 11-36, front: 46-34-22

I'm using the big-big chain sizing method recommended by many. Of course though when pulling most of the slack, my master link lines up with an outer link. So instead of adding one link [outer+inner] from the match point to get my cut point, It's suggested to add [inner+outer+inner] and the chain is looking droopy as hell. Rest assured I will never be in a big-big situation, ever. My rear derailleur is mid-cage so I'm worried it won't pick up all the slack I'm affording the chain in scenario 1. I mocked up a 34F to 11R situation, which I do end up in on mellow downhills, and it looked crazy loose.

I cut the chain leaving myself the option to cut again, and took photos. First pic is as recommended by park tool youtube, pull to nearest inner link, add one extra. Super droopy.

Second pic is mock up of what chain slack would look like if I cut one more [inner+outer] link out. Still has slack, feels like it wouldn't be a problem in any normal gearing. 

RD arrives in the mail today. If this exercise is foolish until I have the RD installed, I can be patient. Just curious if anyone has made the judgement call to only add .5 links instead of 1 full link.

[Steve]

Brenton, I d mount the RD on at this point and put it through its pace on the work stand.  

Steve

[Richard Rose]

Novice mechanic here but I thought you did the big/big thing with chain mounted through the rear derailleur?

Sent from my iPhone

On Jan 20, 2024, at 3:28 PM, Brenton Eastman <brenton...@gmail.com> wrote:

Hi all,

Rear: 11-36, front: 46-34-22

I'm using the big-big chain sizing method recommended by many. Of course though when pulling most of the slack, my master link lines up with an outer link. So instead of adding one link [outer+inner] from the match point to get my cut point, It's suggested to add [inner+outer+inner] and the chain is looking droopy as hell. Rest assured I will never be in a big-big situation, ever. My rear derailleur is mid-cage so I'm worried it won't pick up all the slack I'm affording the chain in scenario 1. I mocked up a 34F to 11R situation, which I do end up in on mellow downhills, and it looked crazy loose.

I cut the chain leaving myself the option to cut again, and took photos. First pic is as recommended by park tool youtube, pull to nearest inner link, add one extra. Super droopy.

<IMG_3012.jpg>

Second pic is mock up of what chain slack would look like if I cut one more [inner+outer] link out. Still has slack, feels like it wouldn't be a problem in any normal gearing. 

<IMG_3013.jpg>

RD arrives in the mail today. If this exercise is foolish until I have the RD installed, I can be patient. Just curious if anyone has made the judgement call to only add .5 links instead of 1 full link.

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<IMG_3013.jpg>

<IMG_3012.jpg>

[Brenton Eastman]

According to this video https://youtu.be/O0YibMDWBAw and most mechanics I’ve learned from it’s less complicated and yields the same resulting length to bypass the rear derailleur. I think if you do the same exercise with the RD installed, you end up with the same chain length. 

On Jan 20, 2024, at 1:38 PM, Richard Rose <rmro...@gmail.com> wrote:

Novice mechanic here but I thought you did the big/big thing with chain mounted through the rear derailleur?

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[Patrick Moore]

You want to use the big/big method with derailleur attached, leaving the derailleur stretched but not to near seizing or breaking. A half-link's leeway is no big deal since you'll have a derailleur.

Or are you planning a derailleurless multicog bike? (I doubt it but serious question.)

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[Patrick Moore]

Forgot to add: the big/big method is a way of getting the chain length correct for a given derailleur. For a derailleurless drivetrain you want all but very minimum slack removed.

[Brenton Eastman]

Rear Derailleur = Yes.  Mid-cage as stated in original post. 

My fear is that I’m offering too-much slack. I only have one quick link. I’ll probably mock it up with RD at current length before snapping the quick link in place. 

On Jan 20, 2024, at 2:21 PM, Patrick Moore <bert...@gmail.com> wrote:



Forgot to add: the big/big method is a way of getting the chain length correct for a given derailleur. For a derailleurless drivetrain you want all but very minimum slack removed.

On Sat, Jan 20, 2024 at 3:19 PM Patrick Moore <bert...@gmail.com> wrote:

You want to use the big/big method with derailleur attached, leaving the derailleur stretched but not to near seizing or breaking. A half-link's leeway is no big deal since you'll have a derailleur.

Or are you planning a derailleurless multicog bike? (I doubt it but serious question.)

On Sat, Jan 20, 2024 at 1:28 PM Brenton Eastman <brenton...@gmail.com> wrote:

Hi all,

Rear: 11-36, front: 46-34-22

I'm using the big-big chain sizing method recommended by many. Of course though when pulling most of the slack, my master link lines up with an outer link. So instead of adding one link [outer+inner] from the match point to get my cut point, It's suggested to add [inner+outer+inner] and the chain is looking droopy as hell. Rest assured I will never be in a big-big situation, ever. My rear derailleur is mid-cage so I'm worried it won't pick up all the slack I'm affording the chain in scenario 1. I mocked up a 34F to 11R situation, which I do end up in on mellow downhills, and it looked crazy loose.

I cut the chain leaving myself the option to cut again, and took photos. First pic is as recommended by park tool youtube, pull to nearest inner link, add one extra. Super droopy.

<IMG_3012.jpg>

Second pic is mock up of what chain slack would look like if I cut one more [inner+outer] link out. Still has slack, feels like it wouldn't be a problem in any normal gearing. 

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[Garth]

You need the rear derailleur mounted Brenton to test the length. The Park video is greek to me. The RD should look something like this :

 https://www.parktool.com/assets/img/repairhelp/size_002.jpg

These always work for me :

https://www.omnicalculator.com/sports/chain-length

http://www.machinehead-software.co.uk/bike/chain_length/chainlengthcalc.html

I can think of much better combos than running the middle ring and the smallest cog, and yes, that's just me.

[Patrick Moore]

The method works only with chain laced through the rear derailleur. A half-link's difference won't make any difference as to too short or too long.

Install the RD, loop chain around big ring, through derailleur, and around big cog; the rd should be stretched but not to point of binding -- ie, a tiny bit of for/aft movement still left.

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[Patrick Moore]

Exactly.

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[Patrick Moore]

Generally and to all: I've very often decided to use a rd that is far out of spec in chain takeup for a given chainring + cassette combination, for all sorts of reasons. Instances: well, first, the DA 7401 (I think it's the ...01) on my present Matthews for an admittedly close ratio 13-25 10-sp cassette but OTOH paired with a 44/28 wide range "1x + granny." But back in the day a 8 sp Ultegra rd with a 48/38/26 crank and a 14-32 7 sp cassette, just because. With the long hanger on the Spec SJ Team frame it worked well enough: I could shift all 7 in the 36; but -- and this is point -- there was severe chain sag in the grannies and all except the 3 or so biggest cogs (perhaps 5 biggest with the Matthews). But then you don't use the granny with the small cogs.

[iamkeith]

I agree with others, that it'll look better when threaded through a mounted derailleur.  Definitely do NOT remove another link until you try that though.    Even so, I have definitely had cases where I still felt like there was too much slack, and ended up replacing the B-screw with a longer one.  In fact, I was doing that so often that I just bought some in bulk.  (I think my issue is that Im usually trying to maximize gear range, rather than achieve tiny, incremental steps for maintaining cadence.)  In a pinch, you can also turn the B-screw around and thread it from the opposite side.  In that case, UN-screwing it increases the tension.

[Joe Bernard]

Nothing to add to others' advice except definitely keep it too long 'til you're sure. What I look for when derailleur and chain are mounted is a decent amount of room left in big-big so I'm not straining the pulley cage, then I don't care if the small-small is droopy. I may accidentally get into big-big with a panic downshift climbing a hill, but I know I'll never use small-small (and droopy wouldn't hurt anything anyway). 

Joe Bernard