Upgrading 8 speed chainset

pbt150
pbt150 Posts: 316
edited October 2009 in Workshop
I've got a bike with an 8 speed Sora/Tiagra mix groupset. I'm looking to upgrade the chainset, and most of the ones on the market are 9/10 speed. Is it possible to run an 8 speed cassette/chain with a new chainset, if it claims to be '9 speed compatible'? If I need a new chain will a 9 speed chain work with an 8 speed cassette?
FTT
Specialized Allez
http://www.flickr.com/photos/49364032@N03/4820302085/
Steel bike http://www.flickr.com/photos/49364032@N03/4656318147

Comments

  • Monty Dog
    Monty Dog Posts: 20,614
    8 speed cassette and chain will be fine with 9 speed chainset
    Make mine an Italian, with Campagnolo on the side..
  • Al_38
    Al_38 Posts: 277
    a 9/10 speed chainset will work fine with an 8 speed chain:
    The fewer the number of gears the wider the chain is, so a wider chain is quite happy on a slightly narrower chainset. I have a 10speed chainset running on a 9spd bike.

    As to a 9spd chain on an 8spd cassette: I'd advise against it - the chain is too narrow and wont fully engage on the teeth, causing it to slip and giving unintended wear patterns. A similar issue might be had with the jockey wheels in the rear derailleur but this matters less. It might run fine, but you would be much better off matching the chain to the cassette.
  • lock
    lock Posts: 32
    sorry for the hijack but are rear mechs made for differant cassettes,

    i had a 10 speed cass and chain,but changed to a 9 speed cass and chain will it work
    tony
  • andy_wrx
    andy_wrx Posts: 3,396
    @pbt150
    You will be able to run a 9sp chainset with an 8sp chain just fine.

    @pbt150/Al_38
    You will also be able to run a 9sp chain on your 8sp cassette if you want to, but probably not an 8sp chain on a 9sp cassette
    - a 8sp chain is wider externally than a 9sp chain, but internally is about the same
    - the cassette cogs themselves are about the same thickness, but the spacers separating the cogs are narrower for 9sp than 8sp
    - thus a 9sp chain will happily run on an 8sp cassette, but an 8sp chain would take a lot of fiddling with the indexing to get it to run cleanly and would probably constantly be going out of indexing and jump a lot

    @lock
    You can run any Shimano 8sp/9sp/10sp rear derailleur with any 7sp/8sp/9sp/10sp system - the thing that has to match is the shifter and cassette : these must be the same number of speeds.
  • lock
    lock Posts: 32
    cheers
    tony
  • lock
    lock Posts: 32
    went back to shop and changed bits back to 10 speed everything works fine now :lol:
    tony

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