triple crank with 8speed cassette

Discussion in 'Bicycle Mechanics and Repairs' started by woodbutcher, 27 Jan 2018.

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  1. woodbutcher

    woodbutcher Über Member

    Location:
    S W France
    I am seriously out of my depth on this one but can anyone tell me what the issues are likely to be if l try to run a 50 40 30 crank with an 8 speed cassette. Would l need double or triple shifters and what size chain etc etc. Forgive my ignorance but lve not tried this combination before !
     
  2. raleighnut

    raleighnut Guru

    Location:
    On 3 Wheels
    Not a problem but you do need a triple shifter on the left, I run a few bikes with 3x7. Bear in mind you'll need at least a medium cage rear mech though or a long cage if running a wide ratio cassette.
     
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  3. TheDoctor

    TheDoctor Man-Machine Staff Member

    Location:
    Stevenage
    It's not that uncommon. You'll need triple shifters, yes, and the front mech should be for a triple too. 8 speed chain, and adjust the chain as normal so you can shift into the big- big combination.
     
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  4. OP
    OP
    woodbutcher

    woodbutcher Über Member

    Location:
    S W France
    Thanks raleighnut and The Doctor , even one of my limited tech.expertise can understand what you say :smile:
     
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  5. Cycleops

    Cycleops Veteran

    Location:
    Accra, Ghana
    All should be quite straightforward. You'll need to size your new chain but GCN have a three methods video for this on YouTube. Simplest is big ring front to big cog rear(omitting derailleur) plus two links. Make sure you buy a chain with a quick link .
     
  6. OP
    OP
    woodbutcher

    woodbutcher Über Member

    Location:
    S W France
    Will do, thanks for that !
     
  7. Ajax Bay

    Ajax Bay Veteran

    Location:
    East Devon
    To be clear that's 'two' half-links of half an inch or a 'link' of one inch.
     
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  8. mcshroom

    mcshroom Bionic Subsonic

    Location:
    Egremont, Cumbria
    It's a perfectly standard set up. You need a triple front mech, triple shifter for the front (unless you are running downtubes), and a GS or SGS rear mech. At 8sp you can use either a road (medium "GS" cage), or a MTB (long "SGS" cage) rear mech. You can also use 9sp derailleurs no problem.

    My tourer is 48-38-28 (or 42-32-22) with an 11-32 8sp rear. I have a 9sp sora triple front mech, an Alivio 8sp rear, and old 2300 shifters. That's worked fine for over 10,000 miles :smile:
     
  9. OP
    OP
    woodbutcher

    woodbutcher Über Member

    Location:
    S W France
    Gotcha ! thanks.
     
  10. adamhearn

    adamhearn Über Member

    As above though I wouldn't say that 50-40-30 is a common chainring size combination (closest/more 'normal' for off the shelf parts is 48-38-28). However, there's no reason those sizes would cause a problem. Quick links are chain width (aka speed) dependent; KMC's is 7/8 speed compatible.
     
  11. OP
    OP
    woodbutcher

    woodbutcher Über Member

    Location:
    S W France
    Its a vintage Campagnolo Centaur which l bought before l knew what l was going to do with it !
     

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  12. Ajax Bay

    Ajax Bay Veteran

    Location:
    East Devon
    Very nice chainset; and a good chainring combination, even if it doesn't meet @adamhearn 's valid if nit-picky definition of 'common'.
    Triple chainset = triple ergo or STI (shifter). 8 speed cassette = 8 speed Campagnolo ergo and derailleur (if Campagnolo cassette) or if Shimano cassette: STI and Shimano rear derailleur.
    Unless OP already has a square taper bottom bracket (for a triple), they will need one (eg UN-55) with a longish axle length (eg 113mm) to get the chain line correct with a triple.
    Sheldon is well worth a read.
    KMC make 'quick links for all chain (speed) widths. Only those designed for 7/8 speed chains are 'compatible' (with an 8 speed chain which the OP's going to fit).
     
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  13. Vantage

    Vantage The dogs chew toy

    I've run KMC chains on my 48-38-28 8 speed rig for the last 6 years.
    In my experience, you can just fit the chain as it is straight out of the bag, no resizing and stuff. It'll run fine.
     
    woodbutcher likes this.
  14. OP
    OP
    woodbutcher

    woodbutcher Über Member

    Location:
    S W France
    Just in from a belated Burns Night French/Scots supper so best l read your info. a bit later ...on first read it looks very interesting ....thank you.
     
  15. OP
    OP
    woodbutcher

    woodbutcher Über Member

    Location:
    S W France
    I was wondering if l could use mirage 9speed ergo shifters with the triple chainset and 8 peed campagnolo cassette , l have a campagnolo triple front derailleur . Only asking because l happen to have the mirage shifters available !
     
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