Chain shifts too far, outer > middle (sometimes) (14t diff)

Manc33
Manc33 Posts: 2,157
edited March 2015 in Workshop
When I have the chain on the outer (of a triple) and around the middle of the cassette, shifting from the outer to the middle makes the chain shift too far sometimes and past, to the granny ring. Other times the chain "rests" on its left edge on the middle ring, then slips around it.

I have made sure its not the outer limit screw of the mech "pinging" the mech too far across.

I have got a 14t difference on those two chainrings, its 38-52t. Will putting a 40t middle on fix it? :?:

Unfortunately being in the highest gear, then shifting up the cassette a few times, then shifting down to the middle ring... is one of the most common gear changes, I do it at the bottom of every hill... can't have the chain going past the middle ring every time. :roll:

What's annoying is I had it working better than that with the "wrong" shifter on. :lol: But then I didn't have "trim", which it needs.

If I swap to a 40t middle, that makes it a 12t difference, but I always thought you could get away with 14t and that's what you shouldn't exceed?

The front mech is a FD-R443 and is rated at being able to handle "10t minimum" but doesn't say what the max is. Is this around the point it stops working, a 14t difference?

Winding out the cable adjuster to tighten the mech up a bit doesn't help, then it just gives way too much rubbing (trim factored in) because it already was adjusted right and still shifts right across the middle ring.

It doesn't do it every time, if the chain is on the smallest sprocket I can't get it to do it, but go up the cassette any and it does.

Does it sound like simply upping the middle ring to a 40t (from 38t) would fix this?

Comments

  • Primus84
    Primus84 Posts: 109
    That poor bike, put it out of its misery!
  • Manc33
    Manc33 Posts: 2,157
    Primus84 wrote:
    That poor bike, put it out of its misery!

    "Nearly" there though. :lol:

    EDIT: It was doing it intermittently when the bike was upside down but I just gave it a proper run out and I couldn't make it do the overshift, tried with the chain 2/3 of the way up the cassette, halfway etc.

    That R770 shifter is really nice to use as well, feels a lot better than the R440 it replaced.

    One thing though, why so many bloody trim functions on it?

    The R440 lever has just one trim on the middle ring, the R770 appears to have one on all three rings!

    Resting position: Granny ring
    Light click 1: Inexplicable, this click seems to just take up a bit of cable slack, chain stays on granny ring.
    Full click 1: Chain moves to middle ring, always needs "untrimming", for the bigger sprockets.
    Full click 2: Chain moved to outer ring, but is trimmed. Never needs untrimming or trimming here.

    So the shifter has a weird trim on the very first click, then the next full sweep changes it to the middle in a trimmed already state, then the next big push changes it to the outer and again, like the middle, already been trimmed up.

    All in all a sodding weird shifter but hey, its nice quality. The shifting on it must be half the lever pressure required compared to the cheaper and older R440.

    Don't hold your breath but I think my bike is 100%'ed now no chit... no more fettling is necessary.

    The only thing might be if this mech starts changing from outer to granny again I will probably swap to the FD-R773 mech but then I have the problem of a 10sp front mech on an 8sp chain and also the added complication that you need the "FD-R773-2" for a 52t big ring, the FD-R773-0 is for a 50t outer max.

    So is there any point swapping to a FD-R773-2 when I already have the FD-R443 on and working? Honestly I think I can probably just leave it now. :oops: I would love to fettle some more but I can't think of one area of the bike I can make better now.
  • darkhairedlord
    darkhairedlord Posts: 7,180
    There are three options:
    1
    First put the gear lever in the middle position.
    Then slacken off both the stop screws.
    Then adjust the shift cable to get the deraillieur positioned on the middle ring.
    The adjust the two stop screws to suit the granny and big rings.

    2
    Buy a compact and ride the bike instead of fettling it or posting about it (you'll get fit real quick and soon get up that hill)

    3
    Buy a hub gear like.
  • dj58
    dj58 Posts: 2,221
    Primus84 wrote:
    That poor bike, put it out of its misery!

    If Manc33's bike could talk it would be saying "No, no, no, I can't take anymore of this tinkering, please sell me on" :(
  • Manc33
    Manc33 Posts: 2,157
    It was because my front mech was at a slight angle, so the inside of the outer plate brought the chain across too far and the cable had to be wound in too much (under normal circumstances) to make the mech function normally. It had the back of the mech's cage sticking out maybe 4mm from the chainring. :oops:

    Once I turned the mech clockwise slightly, so the outer plate was parallel exactly with the chainrings, it shifts nice and quiet. I found this by just pushing the cage in a bit last night thinking "that would make it all go away".

    Doing this means I can now wind out the front mech cable as tight as its supposed to be, thus the front mech only shifts down as far as it needs to.

    So maybe I really don't need that "flat bar road shifter" and could just use a MTB shifter, but its better on this chainstay length to have a trim on it. The R770 has a trim on all three chainrings for some reason. The first trim is truly useless.

    That cable being wound too loose is also why I said the outer chainring has a trim and doesn't need it, now it does need it again. :lol:

    Why is there a trim first click on the granny, it doesn't move the front mech at all, it seems to just take up a bit of cable slack or something. :shock: