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Tiagra Front Mech expected lifespan?

(11 posts)
  • Started 9 years ago by Kenny
  • Latest reply from I were right about that saddle
  • This topic is resolved

  1. Kenny
    Member

    I installed a brand new Tiagra groupset last Easter. The front mech appears to be non-functional already, despite that bike only having done around 4k miles at most since then. The problem seems to be that the spring to return the front mech back to the inner ring is just not pulling any more, and I have to get off and push it with my (dodgy) thumbs to try to move to the inner ring. Rather annoying.

    I've given it a good clean with water, then tried GT85 and WD40 to loosen it up, to no avail, this thing seems to be done.

    Is that lifespan for a Tiagra front mech normal?

    Posted 9 years ago #

  2. I were right about that saddle
    Member

    @Kenny

    Not normal at all. You've done the full troubleshooting routine?

    http://si.shimano.com/php/download.php?file=pdf/um/SI-5MX0A-001-ENG.pdf

    I'd expect a front mech to last several years barring accidents. They don't really do much after all.

    Posted 9 years ago #

  3. Uberuce
    Member

    Front mech on my Croix is the only bit that didn't get an upgrade to 105 this winter; it was functioning too perfectly adequately to warrant it. Shade over two years old.

    Posted 9 years ago #

  4. Kenny
    Member

    You've done the full troubleshooting routine?

    Yeah, but the problem I have isn't one of those, unfortunately. I'll describe what I think a front mech should be doing, just in case I'm missing the obvious.

    I figure that, once you have the front mech attached to your bike, but without the cable installed, it is naturally in the smallest chainring. You attach the cable, and when you shift up with your STI, it pulls the cable down, therefore dragging the front mech across. When you want to drop back down to the small chainring again, you shift down with the STI which merely loosens the cable tension, and the front mech has a spring in it which therefore pulls the chain back over on to the small ring.

    Therefore, if the trouble I'm having is that the shifting to the small ring isn't working, it's because the spring is not working properly and is stuck, hence why it is staying in the big ring.

    Have I got that right?

    Maybe I have a duff front mech, or maybe it just doesn't like the winter commuting. A 105 front mech appears to be around £15 on Wiggle, so I'm thinking that's what I'll have to do, unless anyone knows of a good way of unsticking the front mech. It's so stuck, the only way I can get it to move at all is to attach it to my bike and force it with both hands; I can't move it from side to side when it isn't on the bike, it's so stiff!

    Posted 9 years ago #

  5. Instography
    Member

    I've had a couple of mechs do that and I put it down to my tendency to sit and spin in the middle ring, relying on the rear cogs, and a very shoddy maintenance routine of leaving things alone and rarely cleaning them. I accept the price of replacement as a good return on the time not spent cleaning etc.

    Posted 9 years ago #

  6. Kenny
    Member

    shoddy maintenance routine of leaving things alone and rarely cleaning them

    I think I'm in much the same boat.

    However...

    After a bit more Googling to see whether I could find a resolution, it seemed to be the case that IWRATS is spot on about front mechs having a much longer life span, and that giving it a good clean repeatedly, and with a toothbrush, could be the answer. So I tried that, and it seems to have paid some dividends already. I can now move it with my hands (just) when it is not on the bike, and when I move it "over", it springs straight back again, just like it should.

    I've given it another spray of WD40 and will leave it overnight. If it is still in the same condition tomorrow, I'll stick it back on the bike and see what happens. I'll take the opportunity to replace the gear inner and a ferrule at the same time, as I think the cable was getting a little sticky around the ferrule which probably wasn't making things any easier.

    Posted 9 years ago #

  7. davey2wheels
    Member

    I recently had a similar problem with the two and a half year old front mech on my mtb commuter. It started binding again last week, about three weeks after the first clean.

    I bought an ultrasonic cleaner and gave the mech the treatment. Not only was it made free to move, all surface rust was removed :)

    Posted 9 years ago #

  8. Dougie
    Member

    Just over 1 year/2k miles for my Tiagra front mech. Lack of cleaning and NEPN to blame although it doesn't get much use as I am not doing many hills so sits in the big ring. LBS gave me back the old one which looks fixable if I ever get round to it. Trying to use/clean the replacement a bit more

    Posted 9 years ago #

  9. Kenny
    Member

    It's still functioning fine today, so I've put it on and cabled it up and it's working well without the chain. Managed to make a mess of changing the gear inner cable, somehow it managed to start to unravel before I'd got the end cap on, so that's in the bin. Last step, put cleaned chain on and we'll see what happens tomorrow on the commute...

    Assuming all goes well, the moral of the story is that a good scrub with a toothbrush and WD40 a couple of times made a world of difference.

    Posted 9 years ago #

  10. Kenny
    Member

    Ok, so that did indeed work - front mech working fine now. Hurrah!

    However, my chain snapped on the way home. Time to start a new thread to ask the next question...

    Posted 9 years ago #

  11. I were right about that saddle
    Member

    @Kenny

    Excellent. (As regards the front mech, not the chain.)

    Posted 9 years ago #

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