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Thread: Front shifting, Ultegra 8000 w/Praxis crank?

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    Default Front shifting, Ultegra 8000 w/Praxis crank?

    Has anyone known this combination to have a consistent issue with dropping the chain on front downshifts? A customer is having fits about it--I haven't seen the bike yet. Any feedback appreciated.
     

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    Default Re: Front shifting, Ultegra 8000 w/Praxis crank?

    The 48/32 praxis cranks aren’t the best, especially on bikes with non optimal chain lines or weird length chain stays (I’m looking at you specialized diverge)

    I don’t love the praxis rings in general but those sub compact cranks seem to be the biggest culprits of issues.
     

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    Default Re: Front shifting, Ultegra 8000 w/Praxis crank?

    Quote Originally Posted by Vancouverdave View Post
    Has anyone known this combination to have a consistent issue with dropping the chain on front downshifts? A customer is having fits about it--I haven't seen the bike yet. Any feedback appreciated.
    I am surprised by this, even though a Shimano 11sp chainset is not used, the new FD is not as fussy as the previous type in regards of the incoming gear cable direction.

    The setup is a complete different thing from what used to be done before:
    -after the usual align vertical/horizontal you start by adjusting the "L" screw to align the FD cage flush to the same level of the large chainring and set the cable tight enough
    -then shift to the "top-trim" position (see below) and adjust the cable tension so to align the two little reference marks on the FD body, the chain is now in the large chainring
    -once done that, make sure you have the largest rear sprocket and adjust the "H" screw to get just enough clearance with the inner face of the FD cage. you are still in the "top-trim" lever position
    -next step is to shift down to the small chainring with the shifter in "low-trim" and adjust the "L" screw again
    -then try shift all position for the fine tuning.

    The new Shimano Lh levers have four positions, from inner ring to outer ring in sequence:
    Low-trim <> Low <> Top-trim <> Top
    The "Low-trim" position is the shifter fully released (gear wire in low tension), the "Top" position is the shifter fully engaged (highest gear wire tension)
    Andrea "Gattonero" Cattolico, head mechanic @Condor Cycles London


    "Caron, non ti crucciare:
    vuolsi così colà dove si puote
    ciò che si vuole, e più non dimandare"

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    Default Re: Front shifting, Ultegra 8000 w/Praxis crank?

    What is the suggested method in removing the cable from the Shimano GRX/8000
    series FDs ?. When undoing the cable fixing bolt, the cable carrier wants to rotate,
    mushing the cable.

    For sub compact fans, the GRX crank 48/31 with GRX front mech, shifts very well.
    Now that CX-70 is history, my next project is the GRX 10s front mech with Campaq 10s.
     

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    Default Re: Front shifting, Ultegra 8000 w/Praxis crank?

    Yes, it is a problem with a Specialized Diverge. Do you know about chainlines? I have heard but not measured, the Diverge has a 49mm chain line--about 4 or 5mm further out than ideal for chainrings. Sounds born to produce the problem customer is having.
    Quote Originally Posted by watchcwgo View Post
    The 48/32 praxis cranks aren’t the best, especially on bikes with non optimal chain lines or weird length chain stays (I’m looking at you specialized diverge)

    I don’t love the praxis rings in general but those sub compact cranks seem to be the biggest culprits of issues.
     

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    Default Re: Front shifting, Ultegra 8000 w/Praxis crank?

    Quote Originally Posted by Scott G. View Post
    What is the suggested method in removing the cable from the Shimano GRX/8000
    series FDs ?. When undoing the cable fixing bolt, the cable carrier wants to rotate,
    mushing the cable.

    For sub compact fans, the GRX crank 48/31 with GRX front mech, shifts very well.
    Now that CX-70 is history, my next project is the GRX 10s front mech with Campaq 10s.
    Pull the cage out dropping tension if you have issue
     

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    Default Re: Front shifting, Ultegra 8000 w/Praxis crank?

    It’s been about a year since I dealt with one of these bikes but the very short chain stays, probably incorrect chain line, and praxis crank/ring setup seemed to always be a problem. Swapping to shimano cranks fixed the problem 100% of the time on bikes larger than 49cm.

    From memory the smaller bikes had an unusual seat tube angle and braze on position that caused the FD cage to sit at an angle that was far from concentric with the large ring, these bikes would have never ending chain drop issues and I’ve seen multiple damaged FD’s (cracked and bent cages, broken di2 linkages) from struggling to upshift.

    Quote Originally Posted by Vancouverdave View Post
    Yes, it is a problem with a Specialized Diverge. Do you know about chainlines? I have heard but not measured, the Diverge has a 49mm chain line--about 4 or 5mm further out than ideal for chainrings. Sounds born to produce the problem customer is having.
     

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    Default Re: Front shifting, Ultegra 8000 w/Praxis crank?

    Can you deal with the symptom by adding a chain catcher?
    Colin Mclelland

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    Default Re: Front shifting, Ultegra 8000 w/Praxis crank?

    Some of these mentioned diverges come with a chain catcher as stock, but the fd-r8000 downshifts into the low position which doesn’t fully release the cable so it has a built in catcher of sorts.
     

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