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measuring new chain

snigsnig Posts: 428
edited July 2014 in The workshop
what's the best way to measure a new chain?

I can't use the old one as it will be a different size.

I've watched 5 Youtube videos and each one showed a different way to do it, from large chainring to smallest cassette ring, to largest/largest, and even largest and 2nd largest cassette ring and not threading through the jocky wheel and adding 2 links, I guess they will work but is one method more reliable than the others?

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  • UnderscoreUnderscore Posts: 730
    snig wrote:
    what's the best way to measure a new chain?

    With a tape measure!
    snig wrote:
    I've watched 5 Youtube videos and each one showed a different way to do it, from large chainring to smallest cassette ring, to largest/largest, and even largest and 2nd largest cassette ring and not threading through the jocky wheel and adding 2 links, I guess they will work but is one method more reliable than the others?

    As far as I'm aware (and this is what I've always done), find the point that would allow it to just go round the largest chain-ring and largest sprocket (ignore the derailleur) and add one full link (i.e. two half-links). That's always worked for me when I've not had an existing chain to measure against.

    HTH,

    _
  • The RookieThe Rookie Posts: 27,748
    That is the correct process, and while a slightly different description gives the same result as using the guide that comes with Shimano and also SRAM chains.

    Parktools recommend that method and fully describe it on their website.
  • snigsnig Posts: 428
    Underscore wrote:
    snig wrote:
    what's the best way to measure a new chain?

    With a tape measure!
    snig wrote:
    I've watched 5 Youtube videos and each one showed a different way to do it, from large chainring to smallest cassette ring, to largest/largest, and even largest and 2nd largest cassette ring and not threading through the jocky wheel and adding 2 links, I guess they will work but is one method more reliable than the others?

    As far as I'm aware (and this is what I've always done), find the point that would allow it to just go round the largest chain-ring and largest sprocket (ignore the derailleur) and add one full link (i.e. two half-links). That's always worked for me when I've not had an existing chain to measure against.

    HTH,

    _


    Just read Park tools advice and they say add 2 links, which is a distance of one inch.
  • drlodgedrlodge Posts: 4,824
    Fit it on small-small and adjust to the longest length you can with some tension in the rear derailleur.
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  • anthdcianthdci Posts: 543
    drlodge wrote:
    Fit it on small-small and adjust to the longest length you can with some tension in the rear derailleur.

    this is how i do it, as long as possible without the chain rubbing on itself
  • drlodgedrlodge Posts: 4,824
    anthdci wrote:
    drlodge wrote:
    Fit it on small-small and adjust to the longest length you can with some tension in the rear derailleur.

    this is how i do it, as long as possible without the chain rubbing on itself

    Exactly. That way the chain is as long as possible, and can't be too short.
    WyndyMilla Massive Attack | Rourke 953 | Condor Italia 531 Pro | Boardman CX Pro | DT Swiss RR440 Tubeless Wheels
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  • snigsnig Posts: 428
    drlodge wrote:
    anthdci wrote:
    drlodge wrote:
    Fit it on small-small and adjust to the longest length you can with some tension in the rear derailleur.

    this is how i do it, as long as possible without the chain rubbing on itself

    Exactly. That way the chain is as long as possible, and can't be too short.


    but wouldn't pulling the derailleur too tight leave you with a chain too short?

    you would have to know what position the derailleur should be in at it's tightest point.

    Think the large/large without the derailleur playing a part is the method for me.
  • drlodgedrlodge Posts: 4,824
    snig wrote:
    but wouldn't pulling the derailleur too tight leave you with a chain too short?

    you would have to know what position the derailleur should be in at it's tightest point.

    Think the large/large without the derailleur playing a part is the method for me.

    Using my method, the derailleur can only be too tight if the derailleur doesn't have sufficient capacity. And that has nothing to do with the length of the chain.
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  • anthdcianthdci Posts: 543
    snig wrote:
    but wouldn't pulling the derailleur too tight leave you with a chain too short?

    what do you mean?
    The derailleur isn't not too tight, if anything it is near it's most natural state without the pressure from the chain.

    edit: this guide describes how I do my chain
    http://www.slowtwitch.com/Tech/Chain_How-To_-_Part_1_3279.html
  • mr_evilmr_evil Posts: 234
    The small-small method is best, as then you can change to a larger cassette and the chain will still be long enough.
  • snigsnig Posts: 428
    anthdci wrote:
    snig wrote:
    but wouldn't pulling the derailleur too tight leave you with a chain too short?

    what do you mean?
    The derailleur isn't not too tight, if anything it is near it's most natural state without the pressure from the chain.

    yeah confusing myself was thinking large/large, then you would have to be careful not to pull the derailleur too tight if you were using the derailleur, just adding 2 links would be the safest bet.

    Just tried the small/small and it probably is the better option after all as as you say, the derailleur is at it's max extension and can not be moved past that point, not the case if using the large/large method (I think)
  • The RookieThe Rookie Posts: 27,748
    Small small, what a load of tosh, but then clearly you know more about getting the chain length right than Shimano, SRAM, and KMC or Parktools......

    That and spend a fortune on a lighter bike and carry more weight.....

    I'll stick to the right method which is big/big and at least one pair of links overlap.
  • drlodgedrlodge Posts: 4,824
    The Rookie wrote:
    Small small, what a load of tosh, but then clearly you know more about getting the chain length right than Shimano, SRAM, and KMC or Parktools......

    That and spend a fortune on a lighter bike and carry more weight.....

    I'll stick to the right method which is big/big and at least one pair of links overlap.

    Other than saying "I'm wrong" you provide no explanation or argument. The "big/big and at least one pair of links overlap" method is based on certain assumptions which may not hold true and therefore does not guanantee the correct length, unlike my method which is certain to give you the correct length chain i.e. one that is neither too long nor too short.

    "at least one pair of links overlap" - so do you mean one link, 2 links, 3 links, how many exactly? On my bike there is only one correct chain length since I am at the capacity of my rear derailleur (34-50 and 12-29) and your method is too error prone.

    No idea what you are going on about with the weight bit, its clearly irrelevant to the topic. The Rookie indeed.
    WyndyMilla Massive Attack | Rourke 953 | Condor Italia 531 Pro | Boardman CX Pro | DT Swiss RR440 Tubeless Wheels
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  • The RookieThe Rookie Posts: 27,748
    The right method guarantees it's not to short, as it provides the right length for the 'longest case', it also guarantees it's not to long unless you have the wrong mech, in the same way your small small can't guarantee it's long enough if the rear mech is wrong (capacity), having said that being too short is the more dangerous as it pulls the mech into the cassette, so I'll stick to the one hat guarantees it's not to short rather than hoping it's all specced right so may not be too short.

    I would have thought it rather pursuasive that the worlds two largest drivetrain suppliers (chains, mechs, chainwheels and cassettes) use a method that although worded slightly differently gives the same length as the one I'm suggesting.
  • drlodgedrlodge Posts: 4,824
    Actually I think we are both right :wink: - both methods are doing the same thing, but from different perspectices (small-small vs big-big). Therefore as long as the rear derailleur is of sufficient capacity, both methods will work just fine. Which ever method is used I would always suggest double checking the chain in both small-small and big-big to ensure both extremities are ok. Manufacturers will suggest the big-big method to safeguard against numpties using rear derailleurs of insufficient capacity since, as you say, you really don't want to have a chain that's too short.

    I guess the reason why I prefer my method is that is gives a chain length as long as possible and therefore no need to worry if you change the rear cassette for one with a lower bottom gear (e.g. changing from 12-25 to 12-28). Using small-small, the chain is already the "right" length, but using big-big it'll be too short and you'll need a new chain (or insert some links that you previously removed, if you still have them).

    I recently changed from 12-27 to 12-29 and had I used big-big to size the chain, I would likely have needed a new one.
    WyndyMilla Massive Attack | Rourke 953 | Condor Italia 531 Pro | Boardman CX Pro | DT Swiss RR440 Tubeless Wheels
    Find me on Strava
  • The RookieThe Rookie Posts: 27,748
    drlodge wrote:
    I guess the reason why I prefer my method is that is gives a chain length as long as possible and therefore no need to worry if you change the rear cassette for one with a lower bottom gear.
    Alternatively, I prefer it as short as possible as it weighs less (and the weight loss is free - in fact it gives me longer spare sections for possible repairs), also the rear mech gives better chain control ( - through it's operating angle and controlling less weight) though less applicable on my commuter (only 2 bunny hops each way) than on my MTB's (lots of clattering around).

    Having once had the rear mech go into the cassette on a borrowed bike, I'd never want to repeat that, although as long as the 'small - small' is double checked on big big, I guess that is no less likely to happen.
  • mr_evilmr_evil Posts: 234
    The Rookie wrote:
    ...The right method guarantees it's not to short, as it provides the right length for the 'longest case', it also guarantees it's not to long unless you have the wrong mech, in the same way your small small can't guarantee it's long enough if the rear mech is wrong (capacity), having said that being too short is the more dangerous as it pulls the mech into the cassette, so I'll stick to the one hat guarantees it's not to short rather than hoping it's all specced right so may not be too short....
    If you size the chain big-big, then swap cassettes, you can then end up with a chain that is too short. That's much more likely than someone starging off with a mech with insufficient capacity. Small-small ensures that the chain will be long enough in this case.
    The Rookie wrote:
    ...I would have thought it rather pursuasive that the worlds two largest drivetrain suppliers (chains, mechs, chainwheels and cassettes) use a method that although worded slightly differently gives the same length as the one I'm suggesting.
    They obviously don't expect end users to swap cassettes, or don't care if doing so will require that they purchase a new chain.
    The Rookie wrote:
    ...in fact it gives me longer spare sections for possible repairs...
    You should not repair chains like that. Unless it is still new, the spare links will be shorter than the ones already there.
  • t4tomot4tomo Posts: 2,643
    Mr Evil wrote:
    The Rookie wrote:
    ...in fact it gives me longer spare sections for possible repairs...
    You should not repair chains like that. Unless it is still new, the spare links will be shorter than the ones already there.

    Indeed, your better off with a slightly longer chain on the bike, then if it snaps whilst you are out you can repair with a quick link (which often necessitates sheding a half link or two) and not leave tyour chain too short.
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  • The RookieThe Rookie Posts: 27,748
    Well this is the first time on this forum anyone has suggested anything but big big, why carry more weight and lose chain control when you don't have to.

    If you fit a bigger cassette, fit a new chain or lengthen it!

    Personally I think it's stupidity to have it any longer than needed, no good reason and lots of bad ones, so I'll stick to what the experts (as above) say is right thanks.
  • bianchibobbianchibob Posts: 306
    Try this link....has always worked for me.

    http://www.epicidiot.com/sports/chain_l ... ulator.htm
  • supersonicsupersonic Posts: 82,708 Lives Here
    The derailers are not always of sufficient capacity - the 'big-big' method means you have no chance of causing damage should you go into this combo. I have seen frames bent from chains too short, and I see far too many derailers of insufficient capacity. Even on new bikes!
  • drlodgedrlodge Posts: 4,824
    tenratdep5 wrote:
    The small-small method is best, as then you can change to a larger cassette and the chain will still be long enough

    Indeed, my preferred method as this puts the chain as long as possible. I understand where the "big-big" guys are coming from but in the end, a derailleur of insufficient capacity is going to cause issues which ever way you choose, you should *always* double check big-big and small-small after fitting.

    Its not an issue with my bike, since there is only 1 length that is the right one and is going to work!
    WyndyMilla Massive Attack | Rourke 953 | Condor Italia 531 Pro | Boardman CX Pro | DT Swiss RR440 Tubeless Wheels
    Find me on Strava
  • The RookieThe Rookie Posts: 27,748
    Yes but use big-big and it just goes slack if the mech doesn't have the capacity, get the chain too short and major damage to bike and rider can ensue......fail safe would be big big
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