SRAM red front mech - wont go to big ring

dazzTurning
dazzTurning Posts: 67
edited May 2014 in Workshop
Things were shifting OK today and then suddenly I tried to go from the small to the big (compact) chainrings and it just wouldnt get into the big cog.

It just rubs and rubs but never pushes the chain to the big ring.

Since getting back, I have tweaked and tweaked and nothing works. The limit screw is at its lightest and there is lots of cable tension (I cant get it any tighter),

Things I have tried:

- Making it parallel to the chain rings
- The bottom of the mech is about 2mm from the big chainring when on the small cog.
- Undoing the limit screw (its as loose as it goes).
- tightening the cable

I measured my chain wear and its about 0.75

I have "manually" put the chain on the big ring, and it stays. It just wont shift from the small to the big...

Any help would be great!

Thanks

Comments

  • tuneskyline
    tuneskyline Posts: 370
    You could have a small mouse in your down tube
  • dazzTurning
    dazzTurning Posts: 67
    huh?
  • diamonddog
    diamonddog Posts: 3,426
    SRAM seem to need a fair amount of tension in the cable when on the small ring to work correctly for lifting to the large ring. I have had the same problem after new front mech cable was fitted.

    Ignore the inane comment about a mouse from the above poster, they have posted it in different threads 3 times at least and obviously think it's hilarious. :roll:
  • dazzTurning
    dazzTurning Posts: 67
    The thing is, I cant get the mech to move any further out than it is. (the limit screw is as loose as it can go without falling out...)

    If I angle it away from the bike, then the crank arm rubs it.
  • diamonddog
    diamonddog Posts: 3,426
    There are some SRAM specific vids on YouTube for setting it up, well worth a look, they can be a fiddle to set up.
  • dazzTurning
    dazzTurning Posts: 67
    I just dont get it. The limit screw is as loose as it goes, the cable is as tight as I can make it (when in the small cog). The mech just donest appear to push the chain over far enough. I also have about a 2mm gap between the outer edge of the mech cage and the pedal crank...
  • dazzTurning
    dazzTurning Posts: 67
    I have come to the conclusion the front mech is just crap. It always was very sluggish and felt "fragile" when shifting from small to big. Whats a better replacement front mech?

    Thanks
  • diamonddog
    diamonddog Posts: 3,426
    I doubt the front mechs crap I have Sram and it is still fine after many miles, check the cable is seated correctly at the shifter and that it is not sticking. If the outer cables are worn it could be sticking there. It does sound like a cable issue IMO, possibly may be ready for new cables.
    They can be apita to set up.
  • sungod
    sungod Posts: 16,559
    i've got sram red (2010 version) and no issues front shifting in over 4 years, so it's not as simple as the front mech being no good

    the ti cage is slightly flexier than (heavier) steel ones, but really only noticeable shifting under high loads

    is the cage distorted?

    check the screw that joins the rear end of the cage is ok

    check that the chainring bolts are tight and the rings true

    look a the inside of the big ring, are all the little pins that lift the chain to shift it ok?

    once that's done, check that the mounting for the mech is ok, if it's band-on, make sure it's tight, if it's riveted, any sign that a rivet is loose etc., if you hold the front mech and try wiggling it against the mounting, is there any play

    with the bike on a stand, or just upside down if you've no stand, turn the cranks and (assuming the cable is exposed) pull the cable under the downtube sideways to increase tension, this will certainly ram the mech hard against the limit stop

    if it doesn't shift under those conditions and all the other checks are ok, with the bike on a stand you should be able to look closely at exactly what is happening

    front mechs are simple, they push on the chain to move it
    my bike - faster than god's and twice as shiny
  • styxd
    styxd Posts: 3,234
    Yeh, crap front mechs. A good replacement is an Ultegra 6600, these work very nicely with SRAM shifters (been using them for a few years now after having issues similar to yours with the original SRAM mech)
  • pippi_langsamer-2
    pippi_langsamer-2 Posts: 1,470
    Utter crap front mechs. My Force FM just seems to "de-tune", itself constantly. Never had this issue with several decades of shimano.

    yes, yes, why don't I change then. I will....once it dies!
  • sungod
    sungod Posts: 16,559
    and yet mine is fine, applying logic, either i've got a unique sram red mech or there's something wrong in your set up
    my bike - faster than god's and twice as shiny
  • Serious Cat
    Serious Cat Posts: 489
    sungod wrote:
    and yet mine is fine, applying logic, either i've got a unique sram red mech or there's something wrong in your set up


    Don't forget a muppet suggested a mouse was in his down tube, guess the bike will be off to NSPCA to have it safely removed.
    This serious internet site..............I serious cat
  • dazzTurning
    dazzTurning Posts: 67
    It was ok, then after I had done a climb I tried to shift and it just grated and grated against the inside of the mech.

    It was very wet today, so can only think its something to do with water/grit in the cables? Although, the mech still doesnt look like it can go far enough over before it hits the limit stop (which is at its loosest).
  • sandyballs
    sandyballs Posts: 577
    sungod wrote:
    and yet mine is fine, applying logic, either i've got a unique sram red mech or there's something wrong in your set up

    Sorry to say you are not unique, my SRAM Red has also worked fine for over 3 years. Cable tension is the usual cause for poor shifting along with people not having the right skills. Not saying which it is in case but as long as the mech and shifter are not damaged then clearly it is a set up problem.

    To get max tension I usually put the chain on the top ring and without turning the crank click the shifters down to the small ring, the mech should butt against the chain. With the mech in this position tighten the cable more.

    As for the limit screws there should clearly be enough movement to allow the mech full movement pictures might help.
  • pippi_langsamer-2
    pippi_langsamer-2 Posts: 1,470
    A front mech is not rocket science in my book, but in 30 years of cycling, I've never known a front mech require such "nannying", to get to work consistently well...

    It loses tension, and thus the ability to upshift, but then seems have too much tension to enable downshift! And then decides to throw the fcuking chain right off the outer ring!
  • styxd
    styxd Posts: 3,234
    Poor SRAM front shifting is pretty well documented. Just google search it. You're better off with a 6600 or 7800 mech, you can pick em up 2nd hand for not much money.
  • pippi_langsamer-2
    pippi_langsamer-2 Posts: 1,470
    styxd wrote:
    Poor SRAM front shifting is pretty well documented. Just google search it. You're better off with a 6600 or 7800 mech, you can pick em up 2nd hand for not much money.

    I'd be better of using my bloody fingers to be honest.... :?
  • robbo2011
    robbo2011 Posts: 1,017
    I must also be one of the few people that have not really hand any issues with my 2011 Red front mech.

    It works fine and does not need adjustment. I must just be lucky.
  • StillGoing
    StillGoing Posts: 5,211
    And another for never having had a problem in four years of using SRAM Force and Red components. Set the things up properly and they work. I could mention the crap Shimano and Campagnolo FDs I've stripped off others bikes because they insisted they didn't work when it was just their cack-handedness and constant buggering about with the limit screws that caused the problems. Doesn't mean the components are crap.
    I ride a bike. Doesn't make me green or a tree hugger. I drive a car too.
  • dazzTurning
    dazzTurning Posts: 67
    Would a slightly worn chain cause the issue of not engaging the big ring properly?

    I have "manually" put the chain on the big ring and it rides fine. The only problem is going from the small to the big ring... Nothing I do will get it across far enough. It just almost almost almost... catches the big ring but just doesnt commit.

    Chain wear says 0.75
  • StillGoing
    StillGoing Posts: 5,211
    Why not go back to scratch and set it up properly?

    Put the chain in the small ring on the front and big cog on the rear.
    Disconnect the cable to the front derailleur.
    Using the limit screw nearest to the seat tube or furthest from you, adjust the FD so that it is just missing the chain on the inside.
    Reattach the cable to the FD making sure you pull it tight before tightening.
    Try changing to the big ring.
    If it still won't go, then use the limit screw nearest to you to make the necessary adjustments 1/4 turn at a time.
    Make sure you try changing on the front from the biggest and smallest sprockets on the cassette to ensure you aren't dropping the chain on the inside or outside. If you are, again adjust using the limit screw nearest to you.
    I ride a bike. Doesn't make me green or a tree hugger. I drive a car too.

Categories