Putting a 32t ring on my 105 5800 chainset?

minusnothing
minusnothing Posts: 30
edited September 2015 in Road buying advice
Hi,

Can I just replace my 34t small chainring with a 32t chainring, running a short cage rear mech and 28t biggest sprocket?

Cheers,

Comments

  • trailflow
    trailflow Posts: 1,311
    Nope wont work.

    The smallest chainring you can fit on a 110bcd crank is a 33t because if you go any lower the chain will rub on the chainring bolts.

    Also Shimano's new chainsets use a 4 arm bolt pattern (instead of the usual 5). There are no 33t chainrings available for these afaik. Only 34t

    You can get a 32t cassette but you would need to buy a long cage mech.
  • DKay
    DKay Posts: 1,652
    A medium cage rear mech would suffice to run a 32t cassette. You'd also need a longer chain.
    N
    N+1
  • andcp
    andcp Posts: 644
    As an aside, you may be able to run a 32 tooth rear with a short cage. I'm running 34 front/32 rear on a short cage 5700 set up. Anyone you know have a 32 rear you can borrow to find out? (also, I'm not picking a fight with DKay but I didn't lengthen the chain either)
    "It must be true, it's on the internet" - Winston Churchill
  • DKay
    DKay Posts: 1,652
    [url=http://www.bikeradar.com/forums/viewtopic.php?p=19713008#p19713008]Andcp[/url] wrote:
    As an aside, you may be able to run a 32 tooth rear with a short cage. I'm running 34 front/32 rear on a short cage 5700 set up. Anyone you know have a 32 rear you can borrow to find out? (also, I'm not picking a fight with DKay but I didn't lengthen the chain either)

    No worries, but it depends on how long your chain was to start with and what you're wiling to risk. I swapped to a 32t rear cassette from a 28t for a stupidly hilly sportive a couple of weeks ago and didn't change the chain and used my current short cage Di2 6870 rear mech. Screwing in the b-screw I was able to get sufficient jockey wheel clearance and shifting was generally fine across the whole cassette. However, running big/big (I know you shouldn't, but it does happen), the mech and chain where totally maxed-out and weren't happy. I was happy to do the swap, as I did it as a one-off for an event. But, if it were going to be my regular set-up, I'd get the longer mech and chain.
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  • ddraver
    ddraver Posts: 26,391
    [url=http://www.bikeradar.com/forums/viewtopic.php?p=19712880#p19712880]DKay[/url] wrote:
    A medium cage rear mech would suffice to run a 32t cassette. You'd also need a longer chain.

    THAT IS REALLY IMPORTANT!!!!!

    ( :oops: )
    We're in danger of confusing passion with incompetence
    - @ddraver

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