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Can a MTB front mech be used on road triple chainrings?

Manc33Manc33 Posts: 2,157
edited November 2013 in Workshop
Can I use a MTB triple front mech from a 22-32-42T setup... on a road triple chainset that is 30-39-50?

Is 48T the max most MTB front mechs can handle?

Sorry to ask this in the road workshop but it involves road and MTB lol. It's wrong wherever I ask. 8)

I also read that road chainrings are 5mm closer to the frame than on a MTB, which could also outfox the MTB front mech, but who knows.

The reason for needing a MTB front mech on it is I am using some old XTR shifters on a Sora front mech and while this was fine with the Altus MTB front shifter, for some reason they aren't playing well together now I have put the XTR shifter on. I never knew a FD could be "STI" in and of itself.

So my thinking is take the MTB front mech off my old disused MTB and it will be fine with the XTR front shifter, both are MTB components, but then I have the problem of will the MTB front mech even cope with a road triple?

Also does the Tiagra R443 front mech (for use with "flat bar shifters" whatever that means) actually work on mountain bike XT/XTR shifters... or must you use the corresponding flat bar "Tiagra" shifters?

Grrrrrrrrrrrrr lol. It never ends.

After swapping the FD I bet I have to end up putting 22-32-42 chainrings on it and then that will cause something else, it's almost funny.

Posts

  • Manc33Manc33 Posts: 2,157
    It seems the Tiagra R443 front mech works with MTB trigger shifters. One guy said he has used that setup for 8 years, god knows where I read that lol, but I know now. Been "researching" it for about 4 hours. :D
  • BillyMansellBillyMansell Posts: 817
    edited November 2013
    My old Dawes Galaxy worked fine with an LX front mech controlled by Sora STI shifters across a non-compact road triple. I should add that although it was a touring frame it was kitted out as a winter road bike using a mi of road and mtb parts.

    Unfortunately I can't advise on the relative distance of chainrings from the frame as I sold the bike several months ago but from memory it worked very well for the 12 years I had the set up running both in terms of reach and across the variation of ring/sprocket sizes both front and rear respectively.
  • maddog 2maddog 2 Posts: 8,114
    mtb front mech on a road triple chainset - shifting is rubbish - I've tried it

    What you want is a R443 front triple mech and a R440 left shifter.

    If you try and use a MTB shifter with a normal road triple front mech it won't work
    If you try and use a MTB shifter with a flat bar front mech it can work but only on a double

    For a triple setup you need a 443 mech and R440 shifter.

    I've tried all combinations, so I'm not guessing on this.
    Facts are meaningless, you can use facts to prove anything that's remotely true! - Homer
  • deswellerdesweller Posts: 5,175
    I use a MTB front mech and MTB left shifter on my touring bike with a road triple. Have done for years. Works perfectly OK.

    What you want to avoid are combining a road front mech and MTB shifter, or MTB front mech and road shifter. For some reason the design MA for each are slightly different.
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    On Strava.{/url}
  • Manc33Manc33 Posts: 2,157
    edited November 2013
    maddog 2 wrote:
    What you want is a R443 front triple mech and a R440 left shifter.

    For a triple setup you need a 443 mech and R440 shifter.

    I've tried all combinations, so I'm not guessing on this.

    Why is an R440 shifter needed?

    I read in a few places that the R443 front mech will work fine with MTB rapid fire type shifters.

    For example a guy on another bike forum says:

    "This is the setup I've been using for 8 years on various recumbents: FD-R443 front derailleur, "MTB" and "flat-bar" shifters, "road" triple cranksets, and Shimano rear derailleurs. They have always worked perfectly."

    A guy replying underneath him also said...

    "In my basement my wife has a 1999 Specialized Crossroads Pro. It has rapid fire shifters with a road crankset and a Tiagra front derailleur. The front shifting indexes just fine. At around that time that was the common spec for higher end hybrids and for flat bar road tandems."

    The only way the R443 FD won't work is if it is manufactured to work off STI levers or flat bar levers where they have STI internals, if such a thing exists. I suspected those flat bar shifters were STI with them being for road bikes, but apparently not according to odd people here and there..

    Someone even said what if these "hybrid" components aren't rapid fire or STI based and are another thing altogether. :lol:
  • Manc33Manc33 Posts: 2,157
    DesWeller wrote:
    I use a MTB front mech and MTB left shifter on my touring bike with a road triple. Have done for years. Works perfectly OK.

    What you want to avoid are combining a road front mech and MTB shifter, or MTB front mech and road shifter. For some reason the design MA for each are slightly different.

    What size is the biggest chainring?

    I can't see a MTB front mech coping with a 50T chainring. I thought 48 was the max for a MTB FD?
  • Manc33Manc33 Posts: 2,157
    Can't use the Tiagra R443 even if it will work with the MTB front shifter, they only come with band mounts at 28.6mm or 31.8mm and my down tube on the road bike is a 34.9mm. Stupid oversized aluminium!

    I appear to be completely stuck.

    I know you can probably make a bigger band fit on a thinner down tube with a shim, but a FD thats has a band too narrow is never going to fit.
  • Monty DogMonty Dog Posts: 20,614
    In terms of the OPs question - depends on how much room between the tyre and seattube, so worth trying. Can you not use a Tiagra braze-on road mech and band-on adaptor?
    Make mine an Italian, with Campagnolo on the side..
  • deswellerdesweller Posts: 5,175
    Manc33 wrote:
    DesWeller wrote:
    I use a MTB front mech and MTB left shifter on my touring bike with a road triple. Have done for years. Works perfectly OK.

    What you want to avoid are combining a road front mech and MTB shifter, or MTB front mech and road shifter. For some reason the design MA for each are slightly different.

    What size is the biggest chainring?

    I can't see a MTB front mech coping with a 50T chainring. I thought 48 was the max for a MTB FD?

    At the moment it's running a 48T, but it's been turned down for heavy haulage duties. I'm sure I've had bigger on it but can't swear to it.
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    On Strava.{/url}
  • Manc33Manc33 Posts: 2,157
    Gonna swap it tonight.

    The front mech I am trying with the 30-39-50 chainrings is the FD-MC21 aka an 8 speed triple Alivio, not bad not bad lol from a £259.99 FS MTB, I thought it was a cheaper one on it.

    Whats funny is it sort of already works with the Sora FD, but I can do a change from granny to biggest chainring in one sweep and the shifting is too stiff.

    Why on Earth did an Altus shifter work with the Sora but an old XTR one won't? :roll:
  • Manc33Manc33 Posts: 2,157
    Had a go but the clearance is literally 0.5mm between the MTB mech and back wheel.

    Having Marathon Plus on it doesn't help that.

    Past caring now lol, just left the Sora on. I got the XTR to shift a bit smoother by "strategically" putting the cable in the FD the best way I can, I don't think it was quite right before because the pressure needed to shift has improved a bit, like 5% or 10%. Whats funny is the shifting is good on this, I got a "silent chainring shift" before, don't think I have ever had a bike change that smoothly. The XTR rear shifter is bliss.

    I don't know what all this stuff is about a Sora FD and rapid fire shifters having a different amount of cable pulling, because my Altus shifters worked on it, the spacing was right and the spacing is right on the XTR shifters too, its just that working at a different angle than the shifters are used to makes it stiffer to change gear.

    It is about the same as an old school front changer. I remember when triples first came out they were stiff to change gear.

    Triples... has anyone ever had one run perfectly lol. Can't have big chainring and the 1, 2 or 3 sprockets without rubbing, can't have the granny ring and the 8/7/6 sprockets without rubbing, but I take this into account when riding. Gotta love that 11-32 at the back with a 30-50T chainring. Gives it a range of 30F/32R (0.94) up to 50F/11R (4.5).

    One day I will just get a Rohloff hub, all this component nonsense will go away then. Now I just gotta find £1,200 from somewhere...
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