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Mountain Bike triple on Road Bike

jimbop77jimbop77 Posts: 19
edited October 2018 in Workshop
Hi all

I want to get some lower gears on my Ribble winder bike. Currently I have a Tiagra road triple set up with a bottom bracket of RS500 Road bc 1.37x24.

My question is can I fit a MTB triple chainset to this bike to replace the Shimano Tiagra Triple 4703 Chainset - 10 Speed?

If so which one?

thanks for any constructive advice/comments.

Regards

Jim

Posts

  • arlowoodarlowood Posts: 2,551
    JimboP77 wrote:
    Hi all

    I want to get some lower gears on my Ribble winder bike. Currently I have a Tiagra road triple set up with a bottom bracket of RS500 Road bc 1.37x24.

    My question is can I fit a MTB triple chainset to this bike to replace the Shimano Tiagra Triple 4703 Chainset - 10 Speed?

    If so which one?

    thanks for any constructive advice/comments.

    Regards

    Jim

    As a general rule of thumb, MTB chainsets have a longer spindle than road chainsets. As long as you can find and fit the required number of spacers it could work. However you may need to be mindful of the chain line to ensure you get the best shifting.

    Also you need to think about the front derailleur. With a braze on mech you may not have enough adjustment to drop the derailleur so that shifting works with the smaller chainrings. Could be OK for a band on FD
  • Thanks for your comments Arlowood.

    It is brazed on front mech with a little bit of manoeuvre to drop the mech down.

    What spacers are you referring to? Do you have a link?

    Can you elaborate a bit on what you mean by the best chainline?

    Thanks

    Jim
  • timothywtimothyw Posts: 2,482
    So you already have a road triple chainset? What cassette are you using?

    Tiagra 4703 is specced for an 11-32 and will probably also work with an 11-34 so that's a pretty easy gear with 30 teeth on the small ring and 32/34 on the back.

    The problem with the 4703 Tiagra triple is that the 4 bolt chainring design means smaller chainrings are somewhat limited - if you buy yourself/swap with someone the previous generations 5703/4603 road triple chainset, then you can get granny rings as small as 24 teeth - eg here:
    https://www.sjscycles.co.uk/74-bcd-5-arm/?teeth=24

    This will probably be a somewhat safer bet than switching to a mountain bike triple where there are a load of other bottom bracket/front derailleur compatibility issues raised.

    To be clear a 24 tooth chainring might also be beyond the capacity of your current front derailleur but certainly 28t and perhaps 26t should be doable.
  • Thanks Timothy W - I am using a 11-34 cassette currently.

    So you think getting a 5703/4603 road triple chainset would be a better option? Then getting a smaller granny ring?

    Would the 5703 /4603 fit fine with my existing BB?

    Regards

    Jim
  • timothywtimothyw Posts: 2,482
    Hi Jim
    Yep, correct, that chainset will work with your existing bottom bracket - and will take smaller 74mm chainrings as linked.
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