Results 1 to 16 of 16
  1. #1
    mtbr member
    Reputation:
    Join Date
    Apr 2007
    Posts
    44

    2x10: Use full range of cassette without chain rub

    I got a Shimano FD-m770 (10 speed 3x10) front derailleur which I've converted to a 2x10 by tightening up the High limit screw. I've been having a heck of a time trying to adjust it so that I can use the full range gears on the cassette with both the low (22t) and middle (32t)chainrings. It seems that everytime I get close to having the FD adjusted to allow it, the chain will be just barely rubbing part of the FD chain guide, or won't shift properly, etc.

    I understand that it is advised to use the low sprockets with the low chainring and high sprockets with the high chainrings but since Ive eliminated the high chainring I thought this would give me more adjustability with the front derailleur to the use the full range of cassette for both low and middle chainrings. Coming off a 8spd, I had no problem with this. Is this impossible with the tighter spaced 10 speeds? I'd think the middle ring at minimum should be able to use the full range of the cassette (regardless of what shimano says - see left side).

    I think I might be regretting 'upgrading' to 10 speed if I have to shift the FD constantly depending on which gear I'm in the cassette (again, never an issue with the 8 spd, was able to use full range with both low and middle chainrings).

  2. #2
    mtbr member
    Reputation: PerthMTB's Avatar
    Join Date
    May 2011
    Posts
    528
    Yes, you should be able to use teh whole of your cassette without chain rub.

    Can I ask what height have you set your FD at? I say that because many people who use a 3x FD on a 2x setup assume they should lower the FD so that its as close to the new big ring (old middle ring) as possible. This is a mistake, and can give you bad shifting and chainrub just like you describe. It should be at exacltly the same height as if you still had a big ring. Its a long story, but if you're interested in why then this is what I wrote in a similar thread a couple of months back:-

    Some people also drop the front der. height some.

    NOOOOoooooooo! Don't do it.

    If you're keeping the triple FD and 32 ring then leave it just where it is. There's a wider part of the FD cage where the chain runs when in the middle ring so you can use the whole range of the cassette without the chain rubbing on the FD cage. Above and below this are narrower bits to help swift shifting between rings. If you lower the FD, your chain will now be running in a narrower part of the FD cage, shifting will be worse, and you risk chain rub. In fact, if you change your 32T ring for a 36T like many do, you should actually raise the FD a little because of the greater diameter of the 36T ring.

    I know it looks ugly sticking up there now the big ring has gone, but if that bothers you then get a double specific FD.

  3. #3
    mtbr member
    Reputation:
    Join Date
    Apr 2007
    Posts
    44
    I'm not sure of the exact height.

    I've lowered, raised, twisted, and started from scratch a whole bunch of times. I don't have the 'Pro-set Gauge' sticker on the FD but still have the 'Pro-set' plastic block and thought I had it in the right range following Shimano's instructions.

    Frankly, the margin of error was incredibly tight and an incremental raise/lowering had dramatic/poor results that I'd discover only after going through the whole rigamarole. I may start from scratch yet again and ditch the pro-set block and just pull down on the derailleur's cable point to raise the chain guide over the largest chainring and use a penny as a gauge as Park Tool instructs.

  4. #4
    mtbr member
    Reputation: PerthMTB's Avatar
    Join Date
    May 2011
    Posts
    528
    Quote Originally Posted by govertime View Post
    I'm not sure of the exact height.

    I've lowered, raised, twisted, and started from scratch a whole bunch of times. I don't have the 'Pro-set Gauge' sticker on the FD but still have the 'Pro-set' plastic block and thought I had it in the right range following Shimano's instructions.

    Frankly, the margin of error was incredibly tight and an incremental raise/lowering had dramatic/poor results that I'd discover only after going through the whole rigamarole. I may start from scratch yet again and ditch the pro-set block and just pull down on the derailleur's cable point to raise the chain guide over the largest chainring and use a penny as a gauge as Park Tool instructs.
    Ok, you've answered my question right there.

    Lets start at the beginning. A triple FD has three distinct wide sections in the cage where the chain runs when on the big, middle and small rings respectively. These allow you to use the whole cassette at the back without the chain rubbing on the cage sides. Between these wide sections are narrower sections to help the chain transition quickly and smoothly beween rings during shifts. A double FD only has two such wide sections, for the middle and granny.

    When you set up a 3x FD on a triple crank, you set the cage a few mm above the big ring, and everything is automatically lined up so the wide bits correspond to each of the rings, and the narrow bits are between them. When you set up a 2x FD on a double crank, you do similar.

    BUT - you are mixing a 3x FD with a double crank, and trying to do the same thing - positioning it a few mm above your largest remaining ring. Thats your problem. Its still a 3x FD, and even tho the big ring isn't there anymore, the FD needs to be in the same position as if it was, so the chain runs in the right parts of the cage when in the middle and granny rings, for best shifting and minimal chain rub.

    Put a large ring back on just to set up the FD if you've got one. If not, look carefully at the inside of the FD cage - see where there's a wider bit in the middle - thats where the chain should be running when in your 32T ring. Raise or lower the FD until the chain is in this section of the cage. The cage will be sticking up way above the 32T ring, and yes it looks weird like that, but thats how you'll get the best shifting. If looks are a problem, then get a double specific FD.
    Last edited by PerthMTB; 12-03-2012 at 08:58 AM.

  5. #5
    mtbr member
    Reputation:
    Join Date
    Apr 2007
    Posts
    44
    I should have clarified, I've shortened the chain but haven't removed the largest outer chainring yet so I could install the FD properly. I'm installing the FD with the recommended few mm distance above the 3rd chainring not hte middle ring

    BTW, is the outer edge of the FD chain guide supposed to be directly over the 3rd chainring or should the FD chainguide (inner/outer) be centered over the 3rd chainring when measuring the few mm gap?

  6. #6
    mtbr member
    Reputation: PerthMTB's Avatar
    Join Date
    May 2011
    Posts
    528
    Quote Originally Posted by govertime View Post
    I should have clarified, I've shortened the chain but haven't removed the largest outer chainring yet so I could install the FD properly. I'm installing the FD with the recommended few mm distance above the 3rd chainring not hte middle ring

    BTW, is the outer edge of the FD chain guide supposed to be directly over the 3rd chainring or should the FD chainguide (inner/outer) be centered over the 3rd chainring when measuring the few mm gap?
    Sorry, I assumed from what you wrote above (and in your other post) that you'd already removed the big ring! My mistake.

    To answer your question - when setting up the FD the outer plate should be sitting directly above the large ring's teeth, and parallel to the ring, and a couple of mm above it (turn the crank, some teeth are shorter than others!) Set this up first, then install the cable following Shimano's instructions step by step to get the correct hi & Lo settings and cable tension, and you should be able to get rub-free use of all ten sprockets on the rear in any chainring.

  7. #7
    mtbr member
    Reputation: GTscoob's Avatar
    Join Date
    Apr 2009
    Posts
    2,154
    First off: Did you pull a few links out of your chain since you dropped the 44T ring? You'll want to resize (shorten) your chain now since you wont need as long of a chain to cover such a big ring, this will tighten up your shifting, reduce chainslap, and drop some weight off your drivetrain.

    Depending on how rough your terrain is, you might want to keep your FD as low as possible and live with the chainrub. The lower cage also helps with chain retention. Shifting might suffer a bit as described elsewhere in this thread but you'll have less room for the chain to come up and off the rings.

    Since you're using a triple crank you could also gain a little more front derailleur cage clearance by installing an 8 or 9spd mountain triple front derailleur. It'll shift the same but have marginally more room for cross chaining. A lot of people run 10spd chains on 9spd cassettes for this same reason.

    The #1 most reliable way to get rid of chainrub on the FD cage is to stop cross-chaining. This is a 100% effective way to make your chains last longer and have a quieter and more enjoyable riding experience. And it's free!

  8. #8
    mtbr member
    Reputation:
    Join Date
    Nov 2011
    Posts
    2,483
    Things are a little vague here.
    You are using the granny and middle ring.
    You will not be able to use the full range of the rear gears with the granny - it just isn't going to happen.
    You need to be using the normal shifter range for the granny and middle gear - the large ring shifter trigger position will no longer be used.
    I would not change the high limit screw until you are done.
    The cable adjustment sets the derailleur for the middle ring. Set the chain on the middle ring and the smallest rear gear. Adjust the cable so that the chain is just missing the derailleur.
    Now shift to the largest rear cog. If the chain is rubbing on the derailleur, you are more or less out of luck, Depending on where on the derailleur the chain is rubbing, you might be able to swing the derailleur slightly to help.

    If everything is ok, then tighten the high limit screw down and adjust the low limit screw for proper granny position.

    I've never tried this but it should work - you could set the middle shifter position to give you the optimum derailleur position for the middle front to large rear. Then shift to the large shifter position and use the high limit screw to set the optimum position for the middle front to small rear. Now you will have two clicks for the middle position.

    A 9 speed front derailleur might give you a tiny bit more room to work.

  9. #9
    mtbr member
    Reputation: millertm's Avatar
    Join Date
    Jul 2012
    Posts
    461
    In reading your posts I have a question. When you are using your 24T in front are you still wanting to use your 11T in rear? This could cause an issue. I assume that you can use your full 10 gears while using your middle 32T in front. There is no reason that you should be using a 11-15T or even your 17T while in your 24T front. I have seen bash guards in place of the 42T up front and small cage derailers used in a 2X10 conversion but to say you want to use all of your gears in both chainrings is not feasable.

    Mark
    2012 XXL Carve Expert

  10. #10
    mtbr member
    Reputation: PerthMTB's Avatar
    Join Date
    May 2011
    Posts
    528
    In reading your posts I have a question. When you are using your 24T in front are you still wanting to use your 11T in rear? This could cause an issue. I assume that you can use your full 10 gears while using your middle 32T in front. There is no reason that you should be using a 11-15T or even your 17T while in your 24T front. I have seen bash guards in place of the 42T up front and small cage derailers used in a 2X10 conversion but to say you want to use all of your gears in both chainrings is not feasable.
    I beg to disagree. Not only is it possible to use all ten gears at the back with the granny without chain rub, but it is also desireable.

    Yes, there is duplication, and yes cross chaining will increase the wear on the drivetrain, but there's numerous occasions where I would prefer to stay on the granny and just shift up at the rear, rather than do a front change and two or three rear changes to get to the next gear. For example when racing & I don't want to lose momentum, or when going up a hill under strain and a front change would be messy, or when the change up is just temporary and I know I'm going to change down again soon. In all these situations (and sometimes just because I get carried away and don't realise I'm still in the granny) I will use the granny with the 11/13/15/17 cogs, and it works fine - if you set it up properly to start with.

  11. #11
    Mantis, Paramount, Campy
    Reputation: Shayne's Avatar
    Join Date
    Jan 2004
    Posts
    4,410

    Good that it works for you but it won't happen for everyone

    Quote Originally Posted by PerthMTB View Post
    I beg to disagree. Not only is it possible to use all ten gears at the back with the granny without chain rub, but it is also desireable.

    I will use the granny with the 11/13/15/17 cogs, and it works fine - if you set it up properly to start with.
    Good that it works for you but using all the cogs (without rub) with either the 1st or 3rd chainring is a physical impossibility with some equipment. Chainstay length, bb spindle length and seat tube diameter can play a role in how finiky drivetrain set up is.

    I have several bikes where I cannot use the smallest cogs with the inner chainring because the chain rubs on the next chainring.

    Indexed front shifting and f derailleurs with profiled cages also make it difficult to have zero chainrub.
    *** --- *** --- ***

  12. #12
    mtbr member
    Reputation: millertm's Avatar
    Join Date
    Jul 2012
    Posts
    461
    Quote Originally Posted by PerthMTB View Post
    I beg to disagree. Not only is it possible to use all ten gears at the back with the granny without chain rub, but it is also desireable.

    Yes, there is duplication, and yes cross chaining will increase the wear on the drivetrain, but there's numerous occasions where I would prefer to stay on the granny and just shift up at the rear, rather than do a front change and two or three rear changes to get to the next gear. For example when racing & I don't want to lose momentum, or when going up a hill under strain and a front change would be messy, or when the change up is just temporary and I know I'm going to change down again soon. In all these situations (and sometimes just because I get carried away and don't realise I'm still in the granny) I will use the granny with the 11/13/15/17 cogs, and it works fine - if you set it up properly to start with.
    Ok, if that is how you roll. Since you have stated that there is some gear overlap and have also stated the abuse on your cog by pulling your chain accross all ten rear cogs I can not disagree with you. I was just stating the obvious. It might sound like you need to use a 1X10 instead of a 2X10. For me I like the 3X10 because I ride on the street and dirt with one bike.

    Cheers,

    Mark
    2012 XXL Carve Expert

  13. #13
    mtbr member
    Reputation:
    Join Date
    Apr 2007
    Posts
    44
    Thanks for all the feedback.

    After a lot of finagling, I was able to get the whole range of the cassette to play well with my granny and middle rings without chain rub.

    I suppose there may be a slight rub in the granny and 11T but as suggested earlier that combo is rarely used.

    In the end, the solution wasn't a very systematic approach. I followed all instructs to the T. It was patience and a bit of luck on one of many adjustments.
    Last edited by govertime; 12-07-2012 at 04:44 AM.

  14. #14
    mtbr member
    Reputation: PerthMTB's Avatar
    Join Date
    May 2011
    Posts
    528
    After a lot of finagling, I was able to get the whole range of the cassette to play well with my granny and middle rings without chain rub
    Good on ya! Glad it came good in the end.

    It might sound like you need to use a 1X10 instead of a 2X10
    I would if it could give me the range of ratios I need with good granularity, but unfortunately at the moment it can't, so my 2x10 is the best compromise. However, I'm keeping my eye on the development fo the SRAM 1x11 and internal gear hubs, as the future may lie there!

    Good that it works for you but using all the cogs (without rub) with either the 1st or 3rd chainring is a physical impossibility with some equipment. Chainstay length, bb spindle length and seat tube diameter can play a role in how finiky drivetrain set up is.
    Yes, I guess I was being a little presumptious there, and should have added a caveat that I have found it so with bikes I've had, but can't speak for every combination out there. However, I have managed it with quite a range of different bikes - 3x9, 3x10, 2x9, 2x10, 26" and 29er, hardtail and duallie, and the only one that stumped me was a 2x9 hardtail where the chain would rub on the bottom of the FD cage when in the small/small combination, whereas the suspension sag fixed this on an identically set up duallie.

  15. #15
    mtbr member
    Reputation: Saul Lumikko's Avatar
    Join Date
    Oct 2012
    Posts
    1,379
    Quote Originally Posted by Slash5 View Post
    I've never tried this but it should work - you could set the middle shifter position to give you the optimum derailleur position for the middle front to large rear. Then shift to the large shifter position and use the high limit screw to set the optimum position for the middle front to small rear. Now you will have two clicks for the middle position.
    I beg to differ. The limit screw only limits the cage travel, but the indexing comes from the trigger. You can not make the movement between two clicks smaller by adjusting the limit screw.

  16. #16
    mtbr member
    Reputation:
    Join Date
    Nov 2011
    Posts
    2,483
    Quote Originally Posted by Saul Lumikko View Post
    I beg to differ. The limit screw only limits the cage travel, but the indexing comes from the trigger. You can not make the movement between two clicks smaller by adjusting the limit screw.
    You're right, it wouldn't work, The shifter wouldn't click into the detent.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •