Red front mech over shifting

dread_i1
dread_i1 Posts: 178
edited March 2013 in Workshop
Been setting up the new bike today and have been have some issues with the 2012 red front mech, it seems to want to shift over the big ring even with the screw adjusted to the point when it will only just shift up. I also lowered the mech as much as possible. Rest of the kit is sram red shifters and sram s950 chain set.

Any ideas.

Thanks
Jon

Comments

  • StillGoing
    StillGoing Posts: 5,211
    Presumably you've followed the SRAM set up guide on the net? If you have; when you say only just making it on to the big ring, is this a full throw of the shifter or only part throw? It's confusing when you say
    dread_i1 wrote:
    it seems to want to shift over the big ring even with the screw adjusted to the point when it will only just shift up.
    I ride a bike. Doesn't make me green or a tree hugger. I drive a car too.
  • sungod
    sungod Posts: 16,850
    this is the 2012 fd with yaw? presumably the shifter and chainrings are the matching ones

    installation/adjustment is not the same as a traditional fd

    if you didn't follow sram's instructions to set the height and have altered the limit screw settings, you've missed the chance to use the adjustment guide for initial install

    as well as sram's instruction pdf, there's also a video on sram's website showing the process
    my bike - faster than god's and twice as shiny
  • dread_i1
    dread_i1 Posts: 178
    Thanks for the replies so far. After some more research it appears that I have the 2012 red black edition which is not yaw and has the ti cage.

    Regarding my comment, at full throw the mech sometimes pushes the chain over the big ring. When I adjust the limit screw to stop this, shift back to the small ring then try and shift up again the mech will not move far enough to shift, I then moved the limit screw to allow the shift and then I'm back to the beggining with it pushing over the ring.

    Jon
  • sungod
    sungod Posts: 16,850
    hmm, i've got a ti-cage red mech, it took a few goes to get set-up, then was fine

    sounds like the cable tension is too high and/or the cage is at an angle to the chainring

    when shifting, the cage should move out to the limit screw, then as you let go of the shifter it should drop back a smidge, if the tension is too high that won't happen, if the cage is angled this will mess up the points at which the cage engages the chain in small/large positions

    try this...

    set the adjuster on the downtube to minimum cable tension

    loosen the cable clamp on the fd

    with the cable slack and limit screw undone, get the height (upper leading edge cage about 2mm from tips of teeth) and angle right (cage exactly parallel to chainring), if you can remove the chain it's a bit easier to see things

    put chain on big front, rear small

    then use fingers to hold the cage in the outer position just clear of the chain (0.5-1mm), and tension the cable to hold it there (grab cable with pliers/whatever)

    tighten cable clamp enough to hold it

    check the clearance is ok, if it's wrong, try again

    once clearance is ok, fully tighten the cable clamp

    now it's time to set the limit screw, you want it to be enough to allow the chain to shift, but not enough to let it come off, experiment to make sure it shifts ok over the full range (make sure chain length is correct if you plan to try it when on largest sprocket)

    the cable tension will probably slacken a bit as things bed-in, use the downtube adjuster to tweak as necessary

    btw this is my method, not the same as sram's, but it works fine for me
    my bike - faster than god's and twice as shiny
  • dread_i1
    dread_i1 Posts: 178
    sungod wrote:
    hmm, i've got a ti-cage red mech, it took a few goes to get set-up, then was fine

    sounds like the cable tension is too high and/or the cage is at an angle to the chainring

    when shifting, the cage should move out to the limit screw, then as you let go of the shifter it should drop back a smidge, if the tension is too high that won't happen, if the cage is angled this will mess up the points at which the cage engages the chain in small/large positions

    try this...

    set the adjuster on the downtube to minimum cable tension

    loosen the cable clamp on the fd

    with the cable slack and limit screw undone, get the height (upper leading edge cage about 2mm from tips of teeth) and angle right (cage exactly parallel to chainring), if you can remove the chain it's a bit easier to see things

    put chain on big front, rear small

    then use fingers to hold the cage in the outer position just clear of the chain (0.5-1mm), and tension the cable to hold it there (grab cable with pliers/whatever)

    tighten cable clamp enough to hold it

    check the clearance is ok, if it's wrong, try again

    once clearance is ok, fully tighten the cable clamp

    now it's time to set the limit screw, you want it to be enough to allow the chain to shift, but not enough to let it come off, experiment to make sure it shifts ok over the full range (make sure chain length is correct if you plan to try it when on largest sprocket)

    the cable tension will probably slacken a bit as things bed-in, use the downtube adjuster to tweak as necessary

    btw this is my method, not the same as sram's, but it works fine for me

    Thanks for the detailed reply, I'll give it a try when it get home and report back.

    Jon
  • ricky1980
    ricky1980 Posts: 891
    i got the same FD and shifters...i had to play with it a lot to get it perfect.

    here is what i did, which is basically what SRAM tech manual illustrates but there are some trick which they don't say

    1) set the low adjustment screw (the one at the top of the derailleur) while the chain is on small front and large back with the FD not attached to the cable. allow 1mm clearance of FD cage from chain.

    2) attach the cable, use a pair of pliers to pull the cable tight

    3) shift the rear derailleur to highest gear..smallest cog, check for chain rub. if there isn't rubbing you lucked it. if there is...leave it for now

    4) shift the front to large chainring...remember to relax your high screw (the one at the side of the derailleur).

    5) leave the back gear at smallest cog and adjust the high screw till you are 1mm or less clear from the chain and no chain rubbing

    6) you should be set then, but rarely this occurs. you will have chain rubbing. so you need to play around with the angle of the derailleur by finite amount at a time until you have no chainrub. and unfortunatelly you will have to do micro adjustment of the high and low screws till you have it running perfectly.
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  • dread_i1
    dread_i1 Posts: 178
    Thanks for the above replies, just spent the past hour or so trying it get it right. Its not perfect but hopefully it will do for a ride tomorrow. It seems that even the smallest turn of the high screw will change it from not even shifting into the big ring to shifting over the top. Also i'm not sure if the cable is to tight as the down shift feels under a lot of load however winding the barrel adjuster in so the shifter feels nice results in no movement of the mech.

    Any further advice would be great as so far i'm not as impressed with red as I was expecting.

    Jon
  • edten
    edten Posts: 228
    I am familiar with Shimano and Campag but not SRAM however I'm sure the principal is the same. It seems the above posts are missing the cable tension bit which is probably why its only just moving up or not at all. Ricky1980's post is pretty much there but when you get to the cable being attached click the shifter as what should be necessary to move up to the big ring. If it doesn't change up drop it back down and tighten the gear cable by using the cable adjuster on the the downtube of the frame (if internal routing then you should have an inline cable adjuster between the shifters and where the cable enters the frame, if not you're going to really struggle). Just give the adjuster a couple of turns or so. This will shorten the cable thus getting more movement from the front mech cage. If you over do it you will have too much tension and it just won't feel right/ too hard to shift up. Keep dropping back down to the small ring and tightening the cable until it shifts up okay. Note if it isn't moving up to the big ring regardless of how much youre tightening then you probably need to adjust the outer limit screw (anti-clockwise I think) as it may be stopping the cage moving out enough. Once its moving up to the big ring okay you need to check the cage clearance when the chain is on small back and big front. If outer clearance is too much it is more likely to push the chain off. I then adjust the outer limiter screw so there is only a small clearance, say 0.5mm, between the chain and the inside face of the outer part of the mech cage whilst turning the cranks to ensure clearance across the whole revolution (rings aren't always straight) . With campag the above always works perfectly but the technique may need tweaking to suit SRAM. Given all that I would still read the SRAM tech guide for setting up if you havent already.
  • sungod
    sungod Posts: 16,850
    you do have the cable running on the correct side of the clamp bolt don't you...

    also be worth checking the outers and cable stops etc. are all solid/fully seated, if there's any play/compression it will mess up the shifting
    my bike - faster than god's and twice as shiny