Bdhafner
Hello,

I’m wondering if a R8000 front derailleur will shift a 44/28 or even a (gasp) 42/26 chainring combo. And yes I am that old, fat, and beat to need such baby gears.

Thanks,

Brian
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clarksonxc
You'd probably have trouble getting it low enough on that 42T ring to be effective and not hit the chainstay.  It still might work though, if not all that well.
My guess is you'd have better luck getting it low enough for the 44T ring.
IMO, it's not that it wouldn't function if the cage is a few mm higher than ideal; it's that it wouldn't work with the same amount of crispness and reliability.
You could always use a mtn FD and a JTek Shiftmate; that would definitely get low enough.
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Jeb
I'm using an 8000 FD with a 46/34 combo and it works well. It's a braze on so I can't get the derailleur as low as it should be for the 46 but it shifts perfectly for me. There is an adapter that can lower a braze if needed. You might consider a Shimano CX 70 FD as that would more closely follow the chain ring profile.

https://wickwerks.com/products/fit-link-adapter/
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drwelby
There's also the IRD Sub-C front derailleur that was designed for subcompact cranksets.
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Bdhafner
I forgot about the cage/chain stay limiting factor. I’m currently using the R8000 with 46/30 chain rings and have a 0.75 gap between the bottom of the cage and the chain stay. I hope that dropping the small chainring to 26 teeth will not eat up the 0.75 inch gap. I’ll have to do the math in the morning. I thought that the change in radius of the cage with respect to the chainring might affect the shifting and was worried about that.
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HollyBoni
Bdhafner wrote:
I thought that the change in radius of the cage with respect to the chainring might affect the shifting and was worried about that.


It does, big time. I didn't try the specific combo you want, but i've seen that on a few bikes and if the radius didn't match I could never setup the FD properly.
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Crossbones
This set-up is a braze-on CX 70 FD and a 105 3x turned 2x with chain guard, 28t and 38t chain rings. Shifts fine with no issues.
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84098Gravel
I have a White ind vbc crankset 44/28 shifts fine with Ultegra R8000 Di2.
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clarksonxc

Crossbones wrote:
This set-up is a braze-on CX 70 FD and a 105 3x turned 2x with chain guard, 28t and 38t chain rings. Shifts fine with no issues.


How much shorter is the CX70 cage compared to a "normal" Shimano FD cage?

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clarksonxc
I recently installed a 41/33 crankset from WickWerks and the inside edge of my Deore FD rubs the top of the 33T teeth when I shift to the big ring.  I corrected this by raising the FD clamp, but now the outside edge of the cage sits roughly 7mm above the 41T teeth.  Not good.  I am planning on purchasing a Shimano CX70 or Gevenalle BURD; but I wan't to make the right choice before I spend the money.
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Jeb
clarksonxc wrote:
I recently installed a 41/33 crankset from WickWerks and the inside edge of my Deore FD rubs the top of the 33T teeth when I shift to the big ring.  I corrected this by raising the FD clamp, but now the outside edge of the cage sits roughly 7mm above the 41T teeth.  Not good.  I am planning on purchasing a Shimano CX70 or Gevenalle BURD; but I wan't to make the right choice before I spend the money.


Is it possible that an 8 tooth difference is not enough to maintain the proper clearance? OTOH if the shifting is OK I wouldn't worry. My FD8000 will not mount low enough for a 46/30 but the shifting is fine.
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HollyBoni
I've only seen that when the FD was designed for a different size chainring and the radius of the cage didn't match the chainring, or if the FD was designed for a different chainstay angle.

Or if the pivot points were all worn out and the FD had tons of play, but i've only seen that on old 7-8spd stuff. 
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clarksonxc
Jeb - I doubt that WickWerks would continue to manufacture a set of rings in those sizes if the too small difference was a problem.  I really think it's because I tried to re-purpose a Deore mountain derailleur for an application it wasn't meant for.  If I had a 41/28T crankset, I believe this would be a non issue.  Heck, even if I had a 41/30T crank it might go away.  I was just really surprised when I saw where it was rubbing; I had never seen or expected anything like that before.

HollyBoni - I believe FD design is the issue, but it's because of my choices.  If you looked at the profile of the FD, the inner plate on the cage is MUCH lower than a standard road FD.  It lifts the chain fine, but then the inner ring teeth can't clear the bottom of it.

Reading into it further, I'm just going to buy the short cage FD that is sold by Gevenalle.  https://www.gevenalle.com/product/burd-front-derailleur/?attribute_pa_mount=braze-on
WickWerks mentions it in their tech article, but I wanted to see if I could get away with using the 105 FD I had, or using the Deore FD that was sitting in the parts bin.
https://wickwerks.com/short-cage-front-derailleur-solution/


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Bike John
clarksonxc wrote:
Reading into it further, I'm just going to buy the short cage FD that is sold by Gevenalle.  https://www.gevenalle.com/product/burd-front-derailleur/?attribute_pa_mount=braze-on
WickWerks mentions it in their tech article, but I wanted to see if I could get away with using the 105 FD I had, or using the Deore FD that was sitting in the parts bin.
https://wickwerks.com/short-cage-front-derailleur-solution/<


Interested in hearing how that shifts (in general) with an Ultegra-class brifter, compared to the stock Shimano FD. Trim, how responsive, etc.

One thing frame designers haven’t caught up to yet is braze-on mount height for anything smaller than 50/34 chainrings (though I noticed the Checkpoint does seem to have some additional adjustability).
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clarksonxc
Bike John wrote:


Interested in hearing how that shifts (in general) with an Ultegra-class brifter, compared to the stock Shimano FD. Trim, how responsive, etc.

One thing frame designers haven’t caught up to yet is braze-on mount height for anything smaller than 50/34 chainrings (though I noticed the Checkpoint does seem to have some additional adjustability).


John - I think I may have confused my plans here - the Gevenalle FD will be used with a friction shift Paul Thumbie, so I wont be able to report back on pull ratio/trim.  I will say that the braze-on FD that I bought from Gevenalle says it is for 10sp.  The instructions don't mention anything regarding 10 or 11sp shifters.

To get a braze on FD into a lower position, WickWerks makes this adapter:
https://wickwerks.com/products/fit-link-adapter/
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