Forum home Mountain biking forum MTB workshop & tech

Double ring and front mech query

The Big CheeseThe Big Cheese Posts: 8,651 Forum Tart 2010
edited June 2010 in MTB workshop & tech
OK......

I have a top swing, dual pull XT front mech (the new type)

an FSA Gravity Chainset (Double= 22/32t + bash)

Now assuming the bash is the 'large ring' you would think that the indexing would be 1 click... i.e., granny -> Middle

However, I have to click twice to get it onto the middle ring, rather than once. Almost as if it is looking for another ring in between.

Bot stops are set correctly, 1mm from the chain, hi and lo

Any ideas on why I cant just click once

Posts

  • supersonicsupersonic Posts: 82,708 Lives Here
    Chain tension is out. Keep adjusting until it makes the up shift. You have the mech at the right height? You set up as if were a triple.
  • The Big CheeseThe Big Cheese Posts: 8,651 Forum Tart 2010
    Yep, mucked around with the height... I think it may be too high.. piccie!!!

    s1051224.jpg

    Does it need to go lower?
  • supersonicsupersonic Posts: 82,708 Lives Here
    Yep, way too high lol. If there was an outer ring it needs to clear it by 1mm. Use the bash as a guide.
  • AnonymousAnonymous Posts: 79,667
    See that orange sticker on the front mech, with what looks like teeth profiles?
    Well, those teetch profiles should match up exactly with the teeth on the big ring, should it be present.
  • The Big CheeseThe Big Cheese Posts: 8,651 Forum Tart 2010
    See that orange sticker on the front mech, with what looks like teeth profiles?
    Well, those teetch profiles should match up exactly with the teeth on the big ring, should it be present.

    Yep, I know about the triple ring set up with the Orange sticker, just fitting with a double and bash confuzed me for a bit LOL...... :lol:

    Soooooo

    Needs to sit above the bash, say 2mm or so?

    Sonic.... yes I am a plum.... :oops: :lol:
  • AnonymousAnonymous Posts: 79,667
    hang on, did you really think that since you have a twin ring setup, it needed to be even FURTHER up? :lol:

    Actually, I find better shifting with the mech slightly lower than the ideal, I think mine is more or less set up so that the teeth on the orange sticker line up with the, erm, middle? ring.
    What do you call the biggest ring on a twin ring setup? Anyway, whatever it is, that's what the sticker was lined up with on mine.
  • supersonicsupersonic Posts: 82,708 Lives Here
    The mech obviously slopes downwards as you cange down - I just pull on the exposed cable to line the mech up with the outer ring.
  • The Big CheeseThe Big Cheese Posts: 8,651 Forum Tart 2010
    LOL..... normally Im not too bad around a bike (mechanically) but got this one very wrong lol.... tomoz I shall re-index... tha back is fine (and normally a lot harder than doing the front) I just couldnt work out where I was going wrong LOL.. :oops:
  • The Big CheeseThe Big Cheese Posts: 8,651 Forum Tart 2010
    OK fellas....

    Have followed above advise and lowered it as much as I can without the cage fouling the chainstay. Shiftin IS better however I am still getting chain rub on the inside plate of the cage, this happens when I am on largest cog at back and middle ring up front... not much but it is happening. PICS:

    s1051229.jpg

    s1051230.jpg

    Also on largest caog at back and granny up front, there is 0.5mm gap between chain outer and cage inner plate (as per the rules), yet still keep getting chain suck... and pointers?

    Thanks
  • supersonicsupersonic Posts: 82,708 Lives Here
    Sometimes a bit of rub will happen in that gear - try backing off the tension a nit, but make sure it can still shift to the big ring.
  • The Big CheeseThe Big Cheese Posts: 8,651 Forum Tart 2010
    supersonic wrote:
    Sometimes a bit of rub will happen in that gear - try backing off the tension a nit, but make sure it can still shift to the big ring.

    Great stuff... still needs a little more work... I'll hit it again tomorrow..... :)

    It's rideable, but not 100% perfect.. which annoys me! :oops: :lol:
  • nicklousenicklouse Posts: 50,675 Lives Here
    running a 2 ring set up with standard size rings needs the mech in the same place as for 3 rings and you just use the first two clicks.

    read the article on sheldons pages about chain suck.
    What do you call the biggest ring on a twin ring setup?
    err the big ring.

    i would say your mech is too low.

    look at the cage profile and see if it might be better in an other position, you will see the cage is not uniform in shape and design.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • The Big CheeseThe Big Cheese Posts: 8,651 Forum Tart 2010
    nicklouse wrote:
    running a 2 ring set up with standard size rings needs the mech in the same place as for 3 rings and you just use the first two clicks.

    read the article on sheldons pages about chain suck.
    What do you call the biggest ring on a twin ring setup?
    err the big ring.

    i would say your mech is too low.

    look at the cage profile and see if it might be better in an other position, you will see the cage is not uniform in shape and design.

    YEs, I noticed that the cage inner is not 'flat' if you catch me drift, it is moulded with a 'ramp'...

    Do you think that it is somewhere in between fist pic and the last two (the correct height)...

    Thats what I initially thought, set up as per triple, but just dont use the third click.
  • The Big CheeseThe Big Cheese Posts: 8,651 Forum Tart 2010
    Actually Nick, just had a look at it again, if the bash wasnt there, and there was a third ring, the height looks right (according to the sticker)

    Look at the 32t ring and imagine a 44 on there... as per a triple

    In the first pic of the above post, you can see the sticker 'teeth guides' and the teeth of the middle ring, doesnt look too small of a gap (if that makes sense) :lol:
  • nicklousenicklouse Posts: 50,675 Lives Here
    edited June 2010
    looks too low. put it in both small rings and see how far the cage is below the chain.

    not much in it but i feel it could be better positioned.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • The Big CheeseThe Big Cheese Posts: 8,651 Forum Tart 2010
    nicklouse wrote:
    looks too low. put it in both small rings and see how far the cage is below the chain.

    Cheers Nick, will do.

    Ill do it tomorrow (getting ready to go out on the pi55..

    how far below the abovecombo should the lower part of the cage sit.... estimate?
  • AnonymousAnonymous Posts: 79,667
    According to Nik, It sounds like my mech is too low. It's certainly much lower than it was with a triple. I don't have a chainstay for it to clash against though, and it shifts perfectly.
  • jay12jay12 Posts: 6,306
    i have my mech about 2mm above the bash ring when pulled on as far as possible. i set mine up by shifting to 3 on the shifter, then holding the mech above the bash ring by pulling it, then tightening the cable. i only get rub on the mech in gear 2-1 and 1-9
  • The Big CheeseThe Big Cheese Posts: 8,651 Forum Tart 2010
    Have moved it around a little and this is the best setup out of the lot.

    This was taking into account all of the comments above and searching on the net for piccies.

    s1051235.jpg
  • Not using a bottom roller then?
  • The Big CheeseThe Big Cheese Posts: 8,651 Forum Tart 2010
    Nope, although have not ruled out getting one though ;)
Sign In or Register to comment.