Can I use an 8 speed triple sora chainset with MTB shifter?

dazzawazza
dazzawazza Posts: 462
edited October 2008 in Workshop
I have an 8 speed Sora chainset left over after upgrading my road bike a while ago.

After much neglect my MTB commuter needs the badly worn transmission replaced.
I’m hoping that I’ll get away with changing the cassette and chain only, which I have.
However, if the chainset also needs changing, can I use the Sora triple? I have the front derailleur and Octalink BB as well.
I want to spend the least money possible on this bike as the frame is too large and I’m planning to buy a smaller frame and upgrade a few parts when visas and loans have been paid off.

Comments

  • Steve I
    Steve I Posts: 428
    As far as I know Shimano front shifters and chainsets are not interchangeable between road and mtb. You could use the chain set, but you'd need some kind of road shifter to go with it. A friction shifter (e.g. bar end shifter) will work with anything.
  • nicklouse
    nicklouse Posts: 50,673
    it depends on the size of the rings.

    what have you got? also what mech?

    if sora crankset and road mech then yes the MTB shift will work.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • maddog 2
    maddog 2 Posts: 8,114
    mtb front mechs don't really like road triple chainsets, unless the mech is old and was originally designed when mtb chainsets had big rings ( eg. 26/36/46 types).

    plus you have the question of whether the big rings of the road triple c/set will foul on your mtb chainstays. It's rare but it might happen.

    For a commuter then it's probably less important that everything shifts perfectly so it's a possibility. I'd fit the c/set, if it spins okay then see if you can get it to shift half decently. If it doesn't then maybe try and pick up an old DX or XT front mech off ebay (or singletrackworld froum) and go from there.
    Facts are meaningless, you can use facts to prove anything that's remotely true! - Homer
  • maddog 2
    maddog 2 Posts: 8,114
    a mtb shifter needs an mtb front mech

    the road and mtb versions are NOT interchangeable (not for triples anyway)
    Facts are meaningless, you can use facts to prove anything that's remotely true! - Homer
  • Big Red S
    Big Red S Posts: 26,890
    maddog 2 wrote:
    the road and mtb versions are NOT interchangeable (not for triples anyway)

    When did this change?
  • nicklouse
    nicklouse Posts: 50,673
    Opps i had better tell my brazed on front road mech that it had better stop working then.

    Ok it is only a Tiagra and there can be issues with using them on some MTB cranksets but the pull ratio is the same.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • Big Red S
    Big Red S Posts: 26,890
    The market for flat-barred road bikes testifies to their compatability.

    In answer to the OP, you can continue to use your MtB shifter (the bit at the bars) with the Sora crankset, but will probably need a new derailleur.
    If you're desperate, you can sometimes persuade a MtB derailleur to work on a road crankset, but at best it's noisy and inconsistent.
  • Hi, I have the sora front mech and BB spare after the road bike upgrade.
    The largest chainring is a 52.
  • Steve I
    Steve I Posts: 428
    I'm confused. Shimano make specific road shifters for flat bar road bikes because, presumably, mtb has a different pull ratio to road at the front (the rear is the same). Big Red, are you making the claim that mtb front shifters will work with road chainsets from your own experience?
  • Big Red S
    Big Red S Posts: 26,890
    How big is the biggest chainring on the current crankset? How big is the smallest?
  • It's currently a shimano Tx71 48/38/28. This is my second and I have noticed they wear very easily. A new chain and cassette earlier may have helped though.
  • Actually I've just noticed that the cable pull from the existing mech is from the top, whilst the sora mech is from the bottom. So if the current mech can't be used with the sora chainset I probably wouldn't bother as all the brazed on cable guides feed along the top tube of the MTB.
  • Steve I: Shimano make flat bar shifters as some bikes use 10spd transmission and some people don't want XT on their shifter so they make R600 and R700. They pull the same ammount of cable so should work. It'd look a bit wierd thats all, but thats not a bad thing.

    Go singlespeed, then a whole transmission costs from about £35 all in.
    Your LBS could do it for about £40 all in I would have thought.
    I've got a good freewheel on my Langster and my transmission still only cost £50 to replace. It's had about £100 of parts in 6000ish miles. I'm on I think about 0.5p per mile so far.
    jedster wrote:
    Just off to contemplate my own mortality and inevitable descent into decrepedness.
    FCN 3 or 4 on road depending on clothing
    FCN 8 off road because I'm too old to go racing around.
  • I've thought about single speed, but I'm unsure whether one ratio would suit climbing Wimbledon hill then going flat out down Putney hill (and opposite) every day??
  • maddog 2
    maddog 2 Posts: 8,114
    Big Red S wrote:
    When did this change?

    mtb front/left shifters pull more cable than road front/left shifters

    you're okay with rear/right shifters - you can mix mtb and road without problems

    but for the front, they don't mix, hence the existence of flat-bar road shifters. This isn't marketing nonsense - they are different and I've got a toolbox full of shifters tp prove the theory.

    You can easily bodge using a mtb shifter with a road front mech if you run a double or compact (and I've posted about this in the past), but for triples it won't work. Some really low end mtb-type shifters may work with road mechs I admit. My comments are for mid level and above (say deore and up on the mtb side and Tiagra for the road side).
    Facts are meaningless, you can use facts to prove anything that's remotely true! - Homer