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Changing cassette - how many extra chain links needed

t5nelt5nel Posts: 365
edited July 2012 in Workshop
Chaps,

i am swapping my cassette for the Etape and I have a new chain ready as I am sure that the existing will be too short.

Assuming that the current chain is correct length, how many more links will I need in the new chain?

Details
Full Shimano 105 5700
Compact 50/34
Short cage rear mech.
Old Cassette 12-25
New Cassette 11-28
My bikes
MTB - 1997 Kona Kula
Hybrid - Kona Dew Deluxe
Road - 2011 Ribble Gran Fondo, Omega Matrix Ultegra

Posts

  • Mike67Mike67 Posts: 585
    You'll need three extra sections to cover the three extra teeth at the back if that makes sense.

    You can only add sections in pairs though (a full link)

    Probably a good idea to measure the new one from scratch...there's no guarantee the old one was correct.

    I use the around the big front ring, big rear cog (not going through the derailleur) then add a link.
    Mike B

    Cannondale CAAD9
    Kinesis Pro 5 cross bike
    Lots of bits
  • rolf_frolf_f Posts: 16,015
    I'd try the new chain with 4 extra (2 pairs) to start with and see how much slack you have with the large large and small small combinations. If 4 extra is too much, you'll find the chain rubbing back over itself across the rear mech jockey wheels. If four is too long, then it's easy enough to take two more off.
    Faster than a tent.......
  • arlowoodarlowood Posts: 2,527
    Take the guesswork out of the equation by using the calculator in the attached link.

    http://www.epicidiot.com/sports/chain_l ... tm#results

    All you need do is measure the chainstay length as shown in the diagram and input this along with the size of the largest front chainring and rear sprocket (50 and 28 resp in your case).

    Hit the button and hey presto you have the length of your new chain
  • Chris JamesChris James Posts: 1,040
    The chain only wraps around half the cassette. So for another 3 teeth I would add 1.5 links. Obviously that isn't possible so I would add 2 links.

    However, if you are in any doubt just follow Shimano's recommended method (wrap the chain around large chain ring and large cog at back without threading through derailleur. take up slack, add two more links.

    http://techdocs.shimano.com/media/techd ... 689603.pdf
  • sungodsungod Posts: 13,787
    just follow the manufacturer's instructions for the specific rear mech

    for 105 5700, these are in this document...

    http://techdocs.shimano.com/media/techd ... 702204.PDF

    to cut a long story short, for 105 5700, put chain on biggest ring and smallest sprocket, set chain length so that the axes of the jockey wheels are vertically in line

    simples
    my bike - faster than god's and twice as shiny
  • BozmanBozman Posts: 2,518
    2 teeth 1 link for me.
  • andrew_sandrew_s Posts: 2,511
    sungod wrote:

    Mr Shimano doesn't seem to be able to agree with himself :D

    The way I read it is that if you are using standard Shimano chainrings & sprocket sizes, big/small and vertical jockeys gives the best shifting, but that if you stray outside the norm (eg 50/34 & 12-34 MTB cassette) big/big + 2 links is safer as it guarantees that you'll never break your bike by selecting a gear that the chain won't go into.

    On the original question, Chris is correct. 3 extra teeth = 1.5 links, or 2 in practice.
  • t5nelt5nel Posts: 365
    Crikey - what a can of worms!

    Well I put it on last night with 2 extra pairs but it was much too long in 34x28 to the extent that the jockey wheel was rubbing on the chain/cassette. I shortened it 1 pair at a time until this problem went and then checked it at the other extremes and all seems OK. Interestingly in 50x11 the jockey wheels are pretty much vertical by 'accident'.

    Comedy is the chain is now the same length as the one it replaced!

    Thanks for the advice

    Tim
    My bikes
    MTB - 1997 Kona Kula
    Hybrid - Kona Dew Deluxe
    Road - 2011 Ribble Gran Fondo, Omega Matrix Ultegra
  • rolf_frolf_f Posts: 16,015
    t5nel wrote:
    Crikey - what a can of worms!

    Well I put it on last night with 2 extra pairs but it was much too long in 34x28 to the extent that the jockey wheel was rubbing on the chain/cassette. I shortened it 1 pair at a time until this problem went and then checked it at the other extremes and all seems OK. Interestingly in 50x11 the jockey wheels are pretty much vertical by 'accident'.

    Comedy is the chain is now the same length as the one it replaced!

    Thanks for the advice

    Tim

    This probably just means that the original chain was slightly longer than it should have been.
    Faster than a tent.......
  • cyclecliniccycleclinic Posts: 6,865
    Or trying sizing a chain the way a shop does.

    Wrap your chain around the the big ring and big sprocket at the back adn bring the two ends together (do not thread throuigh the mech) and add 1" and join. If you are joining with a master link make sure place one part of your link in one end of the chain before sizing up. Always add your 1" (outer + inner plate) from the next rivet along or you will end up with a short chain.

    For bike with large jockey wheels you may need to add 2", trhis is common on hybrids e.t.c.
    http://www.thecycleclinic.co.uk -wheel building and other stuff.
  • t5nelt5nel Posts: 365
    Rolf F wrote:
    t5nel wrote:
    Crikey - what a can of worms!

    Well I put it on last night with 2 extra pairs but it was much too long in 34x28 to the extent that the jockey wheel was rubbing on the chain/cassette. I shortened it 1 pair at a time until this problem went and then checked it at the other extremes and all seems OK. Interestingly in 50x11 the jockey wheels are pretty much vertical by 'accident'.

    Comedy is the chain is now the same length as the one it replaced!

    Thanks for the advice

    Tim

    This probably just means that the original chain was slightly longer than it should have been.

    Yes agreed prob was too long - I think on a 12-25 (which is less extreme at both ends) you can probably get away with a few different chain lengths. I am pretty happy that what I have now is optimum for 11-28 and going either side *would* cause an issue at one extreme or the other.
    My bikes
    MTB - 1997 Kona Kula
    Hybrid - Kona Dew Deluxe
    Road - 2011 Ribble Gran Fondo, Omega Matrix Ultegra
  • Manc33Manc33 Posts: 2,157
    OK so if you have a cassette with say 4 more teeth, you add 2 links.

    What if you go from a road rear mech aka short cage to a MTB rear mech aka long cage?

    Would love to know because this will solve me wanting to put a 11-32T on my road bike.

    Does the "big to big and add 2 links" work for short and long cage mechs? I guess, but I am going from a short to a long and adding 7 teeth, so 3.5 links, so 4 links just for that + whatever for the long cage mech. Might as well do it since the chain, rear mech and cassette are all superior on my MTB and not in use. Anyway the road bike cassette (some crappy Shimano 2300 12-28T), chain and the short cage rear mech will go nicely on the MTB, with its stupidly small front chainrings (22/32/42).

    Put it this way I (just about) got up the long side of Snake Pass on a MTB with a road cassette on it - 12-23T in the lowest gear of course lol of 22F/23R (0.95) so yeah, it seems swapping the parts will give me better gearing on both bikes, especially since the MTB cassette has a 11T and the road bike has a 12T. Hell I will never understand that, I already found I need a higher gear than 50F/12R but there you go.
  • bianchibluebianchiblue Posts: 344
    Short as sesibley possible chains work best. Just don't use the big ring with the 2 biggest sprockets, you shouldn't be in those gears anyway.

    Chains set too long are a pet hate of mine!!
  • John.TJohn.T Posts: 3,698
    Short as sesibley possible chains work best. Just don't use the big ring with the 2 biggest sprockets, you shouldn't be in those gears anyway.

    Chains set too long are a pet hate of mine!!
    As long as possible without the chain running on the bottom tongue on the cage for me. Totally safe in all gears and I have found gives smoother running, especially on the bottom run in gears towards the big/big end and slicker changes.
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