Nothing I can do about chain rub this time?
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  1. #1
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    Nothing I can do about chain rub this time?

    First off, I understand the concepts of cross-chaining and why we are supposed to avoid it.

    That said, with the following bike setups I have been able to 100% avoid chain rub including in "big-big" gear:
    -2006 Allez with full DA 7800
    ---53/39 and 12-27
    2006 Allez with full Ultegra 6600
    ---50/34 and 12-27
    2006 Allez with full Ultegra 6800
    ---52/36 with both 11-25 and 11-28
    2015 Scott Addict with full Ultegra 6800
    ---52/36 with 11-28
    2015 Scott Addict with full DA 9000
    ---52/36 and 53/39 with 11-28

    I just got a 2018 Fuji Cross and it has the following setup:
    ---Stock Oval crankset with Praxis 46/36 "Levatime" rings
    ---105 5800 shifters
    ---Ultegra RD-RX800 rear derailleur (previously 105 RD-5800)
    ---Ultegra FD-R8000 front derailleur (previously 105 FD-5801)
    ---Ultegra CS-R8000 11-32 cassette (previously 105 5800 11-28)

    Both stock configuration from the shop and post-changes after a few hours of trying, I absolutely cannot avoid chain rub. Is there a chance it's just not possible this time around? I'm fine if that's the case, it would just be the first time for me.

    Also, when I turn the cranks there's a section of the outer ring that seems to be just slightly off because chain rub specifically happens on just a few teeth. Is this more likely due to the chainring or the crankset? It's a tiny margin, likely much less than 1mm but it's there.

    There is not much room to play with. Depending on how things are adjusted the crank comes close to rubbing the front derailleur on highest setting.

    Also, the Fuji has longer chainstays than the Allez and Addict. I would have thought this would make it easier to avoid chain rub, not harder.

    Anyway... any feedback regarding the chain rub?

    Edit: Removed comments about the chainline which I was wrong about at first.
    Last edited by jetdog9; 01-11-2019 at 10:27 PM.

  2. #2
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    Bend the cage.

    In the days of friction shifting, it was common to bend the cage with the jaws of an adjustable wrench to improve shifting or eliminate chain rub.

    You would toe-in either one or both leading ends of the cage to hasten upshifts/downshifts or spread them out to eliminate rub, or create a slight bulge or flare to the trailing half of the cage for the same reasons.

    Assuming your chainline is correct, your setup follows Shimano instructions, and the Shimano 105 stuff caused you no rub, that would be my next step. The cage is steel so it can handle a lot of manipulation without failure.

    Both paddles on the 5800 front shifter have a trim position for the front derailleur which eliminates chain rub. Is it working on your shifters and did you adjust for it?
    Last edited by Peter P.; 01-12-2019 at 03:51 AM.

  3. #3
    'brifter' is a lame word.
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    No, do NOT bend the cage. The new front derailleurs from Shimano (which you haven't used yet) have a completely different set-up procedure than any other derailleur previously. Make absolutely sure that you're following Shimano's instructions to the letter. There are many shop mechanics that do not do this and they get the derailleur to shift but it's not working as well as it could. You should have zero chain rub w/ this derailleur.
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  4. #4
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    Pardon brief answers, on cell phone browser:

    -Stock 5800 setup (with 5801 FD) also had rub I couldn't get rid of. I changed setup partially because of this, but mostly because I wanted a 11-32 cassette that the original RD wouldn't take.

    -Trim settings understood and accounted for, as well as the tension adjustment line on the newer Shimano FDs.
    Last edited by jetdog9; 01-14-2019 at 04:37 PM.

  5. #5
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    So the chain is rubbing the front DR in the big big and in no other situation?
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  6. #6
    'brifter' is a lame word.
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    If everything is adjusted correctly the only thing I can come up with is that the non-Shimano crank is the problem.
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  7. #7
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    Quote Originally Posted by Srode View Post
    So the chain is rubbing the front DR in the big big and in no other situation?
    Yes, this.

    Probably will live with it a bit until I have time to mess with crank / chainings.

    Per cxwrench's comments, wondering if this would work fine with other cranks. I have extra DA 9000s I could throw on to test.
    Last edited by jetdog9; 01-12-2019 at 02:08 PM.

  8. #8
    'brifter' is a lame word.
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    Quote Originally Posted by jetdog9 View Post
    Yes, this.

    Probably will live with it a bit until I have time to mess with crank / chainings.

    Per cxwrench's comments, wondering if this would work fine with other cranks. I have extra DA 9000s I could throw on to test.
    It should.
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  9. #9
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    More messing with it today and I am 100% sure I can't avoid rub with the current setup. I'm pretty sure it's the Oval cranks. I took the Praxis rings off and they are flat, but on the cranks there is a section that will rub for a few teeth's worth of chain when all other things are adjusted to work.

    I can't throw on the Shimano cranks to test because I don't have the right bottom bracket... apparently these Oval cranks are SRAM style with the 24/22 thing going on.

    I got it working well enough such that the rub will only happen in a gear I shouldn't really be in. Maybe better cranks down the line will help.

  10. #10
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    Hmmm. This is certainly interesting as I have no rubbing anywhere on either my 5800 or 6800 drivetrains with a 34/50 Shimano crankset and 11-32T cassette.

    It sure looks like your Oval crankset is the culprit. Can you adjust it to clear big-big at the expense of rubbing in small-small?
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  11. #11
    Schuylkill Trail Bum
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    Oval cranksets are the work of the devil.

  12. #12
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    I don't think so, although I would certainly not mind that and will see what happens with upper limit adjustment after the lower is adjusted as such (it might already be).

    Thanks everybody for the feedback. Another thing is that the return spring on the derailleur might not be as strong as needed or there is too much tension in the cable due to how it is routed even when it's supposed to be slack. The reason I say this is because when I adjust tension so that the adjustment lines meet (exactly per instructions), and later shift into high and back into high-trim, the lines don't always meet up again.

  13. #13
    Rub it............
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    Quote Originally Posted by SPlKE View Post
    Oval cranksets are the work of the devil.

    Last edited by frdfandc; 01-17-2019 at 02:15 PM.
    You can't fix stupid.

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  14. #14
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    Just to clarify (and I think SPIKE's comments might still stand), the cranks are Fuji house brand "Oval Concepts", but with round rings.

  15. #15
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    That setup should trim out just fine on the big ring. They don't like trimming in the small ring due to the chainring spacing, but that's more of a non-issue unless you like cross chaining small/small.
    If it's impossible to get rid of the chain rub even when trimming then something else is going on. Think about it, if the FD is set so that your 46/11 combo is perfect, then going to 46/32 has nothing to do with the crank,, you didn't change gears up front so why would the crank matter. You will have to trim, but that's just how the new toggle FDs are supposed to work.

  16. #16
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    Question: Does it matter which side the wave washer goes on? It's a Praxis conversion bottom bracket... tech doc for the bottom bracket says the wave washer goes on the drive side, but when the shop put it together they put it on the non-drive side...

  17. #17
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    Quote Originally Posted by jetdog9 View Post
    Question: Does it matter which side the wave washer goes on? It's a Praxis conversion bottom bracket... tech doc for the bottom bracket says the wave washer goes on the drive side, but when the shop put it together they put it on the non-drive side...
    It could alter chainline just a bit as wave washers aren't supposed to be completely compressed...I'd have them correct that.
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  18. #18
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    Okay, I finally got it working well enough, although I really don't love the FD-R8000, feels like return spring isn't strong enough although that could be crappy cable routing of this frame.

    In the end:
    -Put the wave washer on the drive side (per Praxis' guidance)
    -Swapped out front shift cable
    -Tightened the cassette a tad
    -Adjusted derailleur position a bit
    -Swapped cranksets to a different Oval Concepts set

    There might be a tiniest, slightest of occasional rub on big-big, but you know what I shouldn't be in that gear anyway...

  19. #19
    'brifter' is a lame word.
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    You should be able to use big/big any time you want. It's designed so that it should work. Makes much more sense than using small/small. There are definitely times when big/big is ok.
    Remember, you should be adjusting the high limit screw (top adjustment) when shifted to big/big and the front derailleur in the T trim position, NOT the Top position. You're looking for minimal clearance, 0.0-0.5mm between the INSIDE of the cage and the chain. You shouldn't have any rub in big/big.
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  20. #20
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    Thanks, I think I got it, towards end of the shakedown ride things went a bit awry because mud got all over the derailleur... now is probably not a great time to be riding trails in Northern California.

  21. #21
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    For the record, never could get it 100% the way I wanted with 3 different Oval cranksets (300, 520, 720) and the same set of Praxis rings... maybe it was the rings.

    I just switched to Ultegra 6800 46-36 setup because I got a 6800 4iiii powermeter. With the full Shimano setup, all good with no issues preventing chain rub.

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