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Crankset set-up

  • 09-08-2009 3:56pm
    #1
    crazydingo
    Closed Accounts Posts: 154 ✭✭


    I know this will seem like an odd question, but is it possible to use two inner rings on a double crankset?
    The idea being that one of the inner rings would be attached where the outer ring would be.
    Is that possible/feasible?
    I want to have some very specific size chainrings on a double but because the sizes have only a 3-tooth difference and they only come as inner rings I would have to use two of those...:pac:


Comments

  • #2
    crazydingo
    Closed Accounts Posts: 154 ✭✭crazydingo


    Nobody knows?


  • #3
    rflynnr
    Registered Users, Registered Users 2 Posts: 1,021 ✭✭✭rflynnr


    As Paul Brady would have it "the answer is 'nobody knows'".

    That said, and assuming we're talking about a road bike, the answer is probably 'sort of (but it might not be a great idea)'. The first issue would be adjusting (dropping) the position of the front derailleur on the seat tube but that's relatively straightforward. However you might have a problem relating to the fact that outer rings have to fit the cranks and are shaped accordingly: admittedly the inner ring will have same BCD (see Sheldon) but looking at the Ultregra and Tiagra setups on two of my bikes, the space for the outer ring on the crank is a few mm wider than for the inner ring so it wouldn't be a snug fit. Furthermore, the bore holes on the inner ring are threaded whereas they're not on the outer ring so I can't really picture how you'd get both rings tight to the crank.

    I'm intrigued though: presuming we're talking about a 39 and a 42, why would you want to do this? Unusual terrain ahead?


  • #4
    crazydingo
    Closed Accounts Posts: 154 ✭✭crazydingo


    I am modifying my fixed gear bike. After I broke my elbow in a crash resulting from a slipping cog/lockring I decided that bolt-on cogs are the way to go.
    Velosolo do a double bolt-on setup which interested me. The fact that there would be no difference in chain length if the tooth-difference between the two ratios matched appealed to me but because there is only a 3-tooth difference between what I had planned to use (16t and 19t) that would require the same difference between the chainrings.
    It's all so complicated, but the bottom line is that I needed to know if it could be done.

    With the inner chainring on the outer position not fitting snug I don't think I would feel too comfortable on my fixie...


  • #5
    Morgan
    Registered Users, Registered Users 2 Posts: 2,481 ✭✭✭Morgan


    It'll depend on the particular chainset and rings you use. As mentioned above the fit mightn't be great with some of Shimano's recent heavily-shaped chainsets. However, with a traditional crankset you shouldn't have any problems. Rather than using two "middle" chainrings, get a couple of non-ramped single chainrings (since you won't be using derailleur shifting). Velosolo should have all you need.


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