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  1. #1
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    Chain length for double crank?

    I had a 36/22 and replaced the 36t with a 32t, but can't find online how to measure the correct chain length on a double.

    On my other bike, I replaced the outside with a bash guard and figured I'd shorten the chain when I replaced it, but when I did the big big measurement, the chain would get jammed on the cassette when shifting multiple gears at once and I had to lengthen it a few links, so that didn't work lol.. So what's the correct procedure to measure the chain length on a double?

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  2. #2
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    Park Tool Co. ParkTool Blog Chain Length Sizing
    If it is a full suspension then you need to do the big-big + 2 links with the suspension in the longest setting.

  3. #3
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    Hmm. I never knew there was an equation lol.. I guess my teachers were right I will use algebra in real life

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  4. #4
    Fat-tired Roadie
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    I use algebra in real life but wouldn't use it for that.
    "Don't buy upgrades; ride up grades." -Eddy Merckx

  5. #5
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    make the chain long enough but not too long. there is probably a way to calculate it but that's a waste of time. run the chain through the gears and derailleurs and make it long enough to clear the big-big combo on your chainrings and cassette.

  6. #6
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    I get that and know how to do it on a 3x setup but when I did it on a 2x it didn't work so I thought I was doing something wrong. I looked online and didn't see anything specific to 2x setups.

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  7. #7
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    On road bikes, it's the same. I'm surprised it gave you trouble on your other bike. I'd look for some other cause. Maybe having a little more tension due to a shorter chain was making your rear derailleur do something weird?
    "Don't buy upgrades; ride up grades." -Eddy Merckx

  8. #8
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    Derailleur was new and adjusted fine.. Added an extra 2 links I think and its fine. I could shift one by one, but shifting 3 gears at a time and it got jammed and didn't shift.

    I'm going to shorten my chain by a link to compensate for the smaller chainring.. I'll see how it measures first and go from there.

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  9. #9
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    SRAM or Shimano? Rear suspension?
    "Don't buy upgrades; ride up grades." -Eddy Merckx

  10. #10
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    Sram x5, fat bike is the new one i need to cut, full suspension with new deore shadow is the one that wouldn't shift, but i added a link or 2 and its fine.

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  11. #11
    Fat-tired Roadie
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    Since you still have the long cage rear derailleur, if you wanted to be conservative you could just remove one link and call it a day. You could remove none and everything should be okay too. I'm not sure if chain slap is an issue on fat bikes...
    "Don't buy upgrades; ride up grades." -Eddy Merckx

  12. #12
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    While a longer cage is not as sensitive to a too long chain as medium and short ones, it's advisable to disregard cage length entirely when figuring out the proper chain length.

    It's "chain around the biggest front and rear, + 2 links".

    Doesn't matter how many cogs or chainrings you have, doesn't matter which derailleur you have, doesn't matter what size things are front and rear... Don't make it too difficult.

  13. #13
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    the biggest mistake is people think "Plus 2 links" means one inner and one outer,... a "link" is actually 2 parts.. the inner and outer plates are one link.. so you need 4 plates added. 2 inner and 2 outer plates equaling 2 links..
    Going to try and bring Trail Tire TV back. go take a look... http://trailtiretv.blogspot.com/

  14. #14
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    Quote Originally Posted by thomllama View Post
    the biggest mistake is people think "Plus 2 links" means one inner and one outer,... a "link" is actually 2 parts.. the inner and outer plates are one link.. so you need 4 plates added. 2 inner and 2 outer plates equaling 2 links..

    I think you may have that wrong, I'm pretty sure 1 link is 1/2 inch and 1 inner+1 outer link=1 inch (2 links).

    Maybe I'm the one who has it backwards though, during my entire career working on bikes I had never heard of, nor used the "big/big plus 2" method and only found out about it here on mtbr after retiring from that work.

  15. #15
    Trail Tire TV on blogger
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    Quote Originally Posted by J.B. Weld View Post
    I think you may have that wrong, I'm pretty sure 1 link is 1/2 inch and 1 inner+1 outer link=1 inch (2 links).

    Maybe I'm the one who has it backwards though, during my entire career working on bikes I had never heard of, nor used the "big/big plus 2" method and only found out about it here on mtbr after retiring from that work.
    it's what everyone thinks,.. honestly I wouldn't have know except back in the day when I was building drag cars the aftermarket, high performance, timing chains were based on "links" for purchasing and I ended up with a REALLY long one as I counted plates not links.. was OK.. just made it 2 chains

    if you go to get SS chain parts you can actually buy "1/2 links" which are single sets of plates.

    here...

    Is your Mountain Bike Chain Trying to Tell you Something?

    though many of the manufacturers have just adopted the "1 link =1 plate set" as most people figure it that way. but even then they state when sizing they optimally want "2 links plus the quick link"

    really though, with chains.. adding 2 link sets (4 pieces of chain) is safer,.... you can always shorten it if it's too long....
    Going to try and bring Trail Tire TV back. go take a look... http://trailtiretv.blogspot.com/

  16. #16
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    I'm pretty familiar with half links from working on old beaters "back in the day"

    Maybe I'm just misunderstanding your meaning but I do know that a 114 link chain has 114 pins @ 1/2' each. According to Park 2 links is one set of inner and one set of outer plates- Park Tool Co. » ParkTool Blog » Chain Length Sizing

    Also Sram- https://www.sram.com/sites/default/f...nual-rev-a.pdf

    So two links = one inch, right?

  17. #17
    Trail Tire TV on blogger
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    Quote Originally Posted by J.B. Weld View Post
    I'm pretty familiar with half links from working on old beaters "back in the day"

    Maybe I'm just misunderstanding your meaning but I do know that a 114 link chain has 114 pins @ 1/2' each. According to Park 2 links is one set of inner and one set of outer plates- Park Tool Co. » ParkTool Blog » Chain Length Sizing

    Also Sram- https://www.sram.com/sites/default/f...nual-rev-a.pdf

    So two links = one inch, right?
    no.. but yes.. again depends on manufacturer these days ... a "true link" is one inch.. but even like you've pointed out.. they state 116/114/112 links chain length which is plate count...

    but the original chain length theory of Large-Large +2 links should be Large - Large + 2 inches or 4 plate sets... again.. it's kinda gone by the wayside as the manufacturers have done away with it over the years to avoid issues/confusion and derailleurs are over sized to compensate as they will often do a good bit more chain take up then they are rated at.


    again.. toooo long is better than tooooo short
    Going to try and bring Trail Tire TV back. go take a look... http://trailtiretv.blogspot.com/

  18. #18
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    Quote Originally Posted by thomllama View Post
    no.. but yes.. again depends on manufacturer these days ... a "true link" is one inch.. but even like you've pointed out.. they state 116/114/112 links chain length which is plate count...

    but the original chain length theory of Large-Large +2 links should be Large - Large + 2 inches or 4 plate sets...

    I haven't seen any bicycle chain manufactures describe one link as anything other than 1/2 inch so to avoid any confusion it seems sensible to me to go by bicycle industry standards when describing a bicycle chain link, especially to beginners.

    Also every every bicycle chain brand I'm aware of specifically recommends adding 2 links in the big/big combo based on the definition of one link as 1/2 inch.

    I'm not disagreeing with you that too long is better than too short, I just think it should be clear that your recommendations go against those of component manufactures and repair websites such as Park Tool. I'm pretty sure I've went against their recommendations a few hundred times or so myself because as I already said I never used that method for sizing chains.

  19. #19
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    I think the page that comes with SRAM chains recommend big-big +2 and actually shows a picture with one set of inner plates and one outer.

    I'd rather just count pins, since it's unambiguous.
    "Don't buy upgrades; ride up grades." -Eddy Merckx

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