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  1. #1
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    Front derailleur issues

    Hi. I am installing a Shimano 105 (5703) front derailleur on my bike and it won't shift into the top chainring. The bottom and middle chainrings are fine. I am using 105 STI levers and a 48-36-26 crank. What could I be doing wrong? Please help!

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    Two quick possibilities before we look to odd stuff.

    Either you set the outer limit too tight, or the crankset is out beyond the travel range of the FD. Try shifting from the middle by drawing the bare wire away from the downtube like a bowstring. If it doesn't shift back off the upper limit until it does, or until the limit is backed out all the way and you've run out of travel.

    If you get it to shift by the bowstring method, adjust the upper limit until it makes that shift consistent and reliably without over-shifting. Once the limit is set go back and complete the cable adjustments.

    If you can't get it to shift by the bowstring method, check that there is in fact no travel elft, in which case you need to move your crankset more inboard.
    FB
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    Certified Bike Brat Burton's Avatar
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    I`ll second everything already posted and add the following:

    I`m personally unaware of any ROAD crankset marketed by Shimano that comes stock with the chainrings you listed.

    If you`re attempting to use a road derailleur with a mtb crankset then the chainlines are different and the throw on the road front derailleur probably won`t be enough to accomodate a mtb crankset.

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    I set up the front crank with a 47.5mm chainline. Also no it isn't a road crankset. However I took that into consideration when I chose my crank. I also read the forums and countless people are not having problems with road front derailleurs and non road cranksets. I might just need a narrower bottom bracket. I can barely get the FD over the top chainring...

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    Chainline is only a part of the big picture. Note that the outer of a triple will be farther out than that of a double with the same chain line.

    The seat tube diameter also makes a difference. If you have a braze-on FD on a 1-1/8" steel tube it'll be 1/16" more inboard than the same FD on a 1-1/4" tube. Clamp-on FDs also vary because the makers don't change the geometry when they change the clamps.

    If you're absolutely sure that it can't reach, and you have chainring clearance inboard you could move the cranks in. Or you might consider a triple FD which might have more throw (check index compatibility).
    FB
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    My FD is a triple. It is also a 31.8mm clamp on. I am pretty much at a loss. I really don't want to go to the bike shop here because they are pretty clueless, but I have no real choice.

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    Ok so I just disconnected the shift cable and manually moved the FD and chain to the top chainring. If I held the FD up and spun the crank I had plenty of room. Does this sound more like I have a cable problem?

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    Senior Member CACycling's Avatar
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    Quote Originally Posted by USAF1C1X1 View Post
    Ok so I just disconnected the shift cable and manually moved the FD and chain to the top chainring. If I held the FD up and spun the crank I had plenty of room. Does this sound more like I have a cable problem?
    Did you attempt the "bowstring" method mentioned by FB earlier? That should produce the same result. If it doesn't, perhaps you have the cable routed through the FD clamp wrong. If the FD can physically move out there, it should be able to be moved by the cable.

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    Since you brought it up

    Quote Originally Posted by FBinNY View Post
    Chainline is only a part of the big picture. Note that the outer of a triple will be farther out than that of a double with the same chain line.

    The seat tube diameter also makes a difference. If you have a braze-on FD on a 1-1/8" steel tube it'll be 1/16" more inboard than the same FD on a 1-1/4" tube. Clamp-on FDs also vary because the makers don't change the geometry when they change the clamps.

    If you're absolutely sure that it can't reach, and you have chainring clearance inboard you could move the cranks in. Or you might consider a triple FD which might have more throw (check index compatibility).
    FB you actually covered all the bases in your first posting and from what the OP has since posted - looks like the cable tensioning is the issue because apparently the derailleur has the travel to reach all three chain rings.

    But since you mentioned it - thought I`d ask.

    Shimano is the brand I`m most familiar with and the chainlines of their double cranksets for both road and mtb are measured to the halfway point between the two chainrings.

    The triples, on the other hand, are all measured to the midpoint of the middle chainring. As per Shimano specs, provided the cranks are mounted on the recommended BBs, there is a minimum 5mm difference between a road and mtb chainline and there is none I`m aware of that has an identical chainline speced for both a double and a triple crankset.

    But you`re obviously well informed so I`m thinking that maybe you`ve delt with another situation altogether. In any case - feel like I`ve missed something so please fill me in.

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    Quote Originally Posted by Burton View Post
    FB you actually covered all the bases in your first posting and from what the OP has since posted - looks like the cable tensioning is the issue because apparently the derailleur has the travel to reach all three chain rings.

    But since you mentioned it - thought I`d ask.

    Shimano is the brand I`m most familiar with and the chainlines of their double cranksets for both road and mtb are measured to the halfway point between the two chainrings.

    The triples, on the other hand, are all measured to the midpoint of the middle chainring. As per Shimano specs, provided the cranks are mounted on the recommended BBs, there is a minimum 5mm difference between a road and mtb chainline and there is none I`m aware of that has an identical chainline speced for both a double and a triple crankset.

    But you`re obviously well informed so I`m thinking that maybe you`ve delt with another situation altogether. In any case - feel like I`ve missed something so please fill me in.
    Thanks for the compliment, but I don't think I said anything different than you did. I said that the outer of a triple would be farther than the outer of a double with the same chainline. You correctly describe how to measure chainline, which confirms my statement because the outer triple will be a full step off-line, while the double will only be a half step out. Draw a quick sketch if you need it.

    ----------------

    Meanwhile, to the OP, you've confirmed that the FD is fine since it reaches when shifted manually, so obviously it is a cable or lever issue. Next attach the wire and re-confirm by the bowstring method. and roughly set the outer limit. Now, if you have any barrel adjusters park them all the way in, and shift the lever to low (it is a triple lever I hope) and pull up all the slack and attach the wire to the correct side of the pinch bolt & tighten. Shift the lever to the middle position and adjust the barrel until it shifts, and center the trim. It should now shift to the outer.

    BTW- if you have trouble pulling up all the slack, hold the FD cage out about half way to the middle ring. (on Campys I stick a pencil into the pantograph) This allows you to leave a bit of slack in the cable which the FD takes up as it springs inboard.

    Also, if the FD works but doesn't throw far enough between the middle and outer ring, route the cable to the other side of the pinch bolt (nearer to the arm's pivot) which will increase the response ratio.
    FB
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    An ounce of diagnosis is worth a pound of cure.

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    WARNING, I'm from New York. Thin skinned people should maintain safe distance.

  11. #11
    Senior Member skilsaw's Avatar
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    One more consideration.
    With the derailleur connected to the cable, confirm that when you are on the smallest ring that the shift lever is in the last position.

    As for compatibility, my Cannondale t1 came with STI brifters and a 50/39/30 crank. The 105 front derailleur that came with the bike is a triple. I changed the crankset to an LX 26/36/48 trekking crank and everything works fine. If you have the same parts I do, the combination you are trying should work.

    Keep fiddling with it, and Good Luck.
    The one who has the most bikes wins.

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    Thanks for all the tips. In spite of everything, the cable just will not pull out far enough to shift into the top chainring. I am at a loss. I went to the bike shop here on base and I asked if I could order a bottom bracket. The lady at the counter had no idea what I was talking about and tried to sell me a square taper "hub" (her words not mine). So I might need to get a smaller BB. The problem is that if I get something too narrow, the small chainring will rub on the chainstays. Any other suggestions? I did notice that my bottom bracket (Octalink V2 121mm) is not symmetrical. Are all Shimano Octalink bottom brackets not symmetrical? If it was, it might have worked.

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    Update. I left the bike alone all day. If I didn't I was going to go nuts. Anyways, I re-attempted tonight to get it to work. I raised the FD more than what I thought would be necessary (~4mm) when you consider the 2 tooth difference between the recommended top chainring size (50) and what I am using (48). What do you know. It is working! However, I have another problem. Whenever I use my brifer to shift into the middle chainring from the top chainring, it drops into the bottom chainring. Is this a trim issue or something else?
    Last edited by USAF1C1X1; 03-10-11 at 08:19 AM.

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    Yes, the cable tension is ok??

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    The cable tension is fine. There is no slack at all. I try not to cross chain when I am testing the downshift to the middle ring, but it still jumps all the way down.

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    Quote Originally Posted by USAF1C1X1 View Post
    However, I have another problem. Whenever I use my brifer to shift into the middle chainring from the top chainring, it drops into the bottom chainring. Is this a trim issue or something else?
    This can be caused by too much cable tension. Try reducing the tension slightly.

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    When setting up triples, I use the cable/trim adjustment to optimize shifting to the middle ring from either direction, that usually also provides for the best clearance coming from the middle of the cassette. the goal is to get middle ring trim as perfect as possible. Then the trim for the outer and inner rings usually come out OK but can also be tuned by the limit screws (but only in one direction)

    There are a number of decent tutorials (and some lousy ones) available free on the net. Search front derailleur setup and review a few of them taking the best from each until you light on what you need.
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    Quote Originally Posted by FBinNY View Post
    Thanks for the compliment, but I don't think I said anything different than you did. I said that the outer of a triple would be farther than the outer of a double with the same chainline. You correctly describe how to measure chainline, which confirms my statement because the outer triple will be a full step off-line, while the double will only be a half step out. Draw a quick sketch if you need it.
    You`re welcome! But I really didn`t explain anything, I simply quoted to you how Shimano defines the chainlines for their double and triple cranksets - which specifically states they are different. Which doesn`t confirm your statement and you didn`t actually answer my question.

    But since Shimano specifically markets front derailleurs for their double cranksets and seperate front derailleurs for their triple cranksets - the comparison is pretty irrelavant anyway.

    You can be pretty helpful when you want to be - but I like you better when you skip the techo-speak.

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    I measure chain lines the same way Shimano does. I measure to the center between the inner and outer rings. On a double it's the imagined center-line between the 2 rings, and on a triple it's the actual center of the center ring.

    That means that each ring of a double will be 1/2 the chainring gap away from the center line. On a triple the middle will be right on while the inner and outer will be a full gap away from the centerline. Last time I checked a full gap was more than 1/2 gap, so the outer is more outboard of the chainline on a triple than on a double with the same chainline.
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