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Front Derailleur for 40/24 crankset

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Front Derailleur for 40/24 crankset

Old 10-24-20, 07:21 AM
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jay1680
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Front Derailleur for 40/24 crankset

I am building a bike as a hill climber and one that will be useful for me in my 70s. I have chosen a G30 White Industries 40/ 24 tooth double chain wheel and Genavelle shifters that will be set up for friction shifting for the front derailleur. Does anyone know what front derailleur will work with such a setup? I would actually prefer to use Shimano 105 shifters. Is there a chance that that a 105 FD will work? And finally is a 40/24 on a road bike a bad idea for other reasons?
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Old 10-24-20, 07:51 AM
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First question I have is what frame are you using? If you're using a frame with a braze on derailleur mount, it might not be low enough to accommodate the 24 tooth. Typically Braze on mounts are good for 34Tooth compact and may have room to go a little lower. The crankset you mentioned has a chainline of 45mm. Shimano road front derailleurs have a chainline of 43.5mm. Shimano GRX have a chainline of 46.0mm. Shimano triple has a chainline of 45mm.

I can't post URLs yet but you can search for the Shimano triple front derailleurs to see which one you like.

Adjust the limit screws with the Triple and it should work as long as it's band on and you can get it low enough.
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Old 10-24-20, 07:54 AM
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Regarding the 40/24, I don't see a huge problem. You'll probably just be limited in the top speed end. Regarding 105 front derailleur, it depends on the version. The 7000 series doesn't have the exact same chainline as your crankset. Are you using an older 105 triple (5703)?
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Old 10-24-20, 08:57 AM
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The radius of the outer plate isn’t quite right, but the Microshift Centros (Gevanalle Burd in my case) works great for gravel setups. I use it on a White Industries M30 (even wider chainline) with a 38-22 and it does the trick for me. You will be near the limits of the derailleur and the shifting is not exactly perfect, but it does work.

i run with 10 speed ultegra shifters.
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Old 10-24-20, 12:12 PM
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Originally Posted by ft3safety View Post
First question I have is what frame are you using? If you're using a frame with a braze on derailleur mount, it might not be low enough to accommodate the 24 tooth. Typically Braze on mounts are good for 34Tooth compact and may have room to go a little lower. I
It's not the inner chainring the fd mount has to satisfy, it's the larger chainring. The derailleur should be positioned low enough to just clear the 40T outer ring.
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Old 10-24-20, 03:24 PM
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The Frame will not have a mount. I will use an FD with clamp. I will be using a Shimano road derailleur with a chainline of 43.5. and yes the White Industries crank has a chainline of 45 mm. Is the 1.5 mm difference a problem? The drivetrain will be Shimano 11 speed. Could I use Shimano 105 brifters and instead of the Genavelles ?
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Old 10-24-20, 03:47 PM
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Bill Kapaun
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People obsess about a couple MM of chainline.
In MOST gear combos, you are WAY more misaligned then that.
The whole point is to have the chain lined up straight between the rings & cogs.
Unless you have a triple and odd number of cogs AND use only the middle ring AND middle cog, you are cross chaining to some degree.
I tend to use the middle ring & smaller cogs, so I set my chainline a little "wide" to have the chain run "straighter" a greater % of the time.

The only other chainline issue is that it be such that the FDER can reach all the rings satisfactorily.
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Old 10-24-20, 05:16 PM
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They were recently discontinued (I think ???), but you may still be able to find a Shimano FD CX-70 front derailleur. Designed especially for compact doubles and cyclocross. Works nicely on triples too. I have them on two bikes. Very nice.
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Old 04-02-21, 02:27 PM
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In case you're still thinking about it, I have 44/24 chainrings and I got it to shift ok, both with either shimano fd 4700 and sram yaw fd. The chain will rub the outer chainring when on the inner chainring if going over the 7th cog but I don't need the 8,9,10 while on the inner chainring.

There are some times when the chain will not shift to the outer chainring when it gets pressed into a bad orientation against the ramps so I just back off and try again. But 90% of the time it will work smoothly. A chain catcher is needed to prevent the chain from falling off the inner chainring when down shifting. The sram chain catcher is pretty good with an adjustable screw to tune the clearance and it comes with the sram yaw fd. It's just long enough for a 20t jump, maybe 22t.

The shimano 4700 needed trimming. The sram yaw does not need trim, and I was able to use the 4700 long pull trigger shifter with the sram yaw fd after blocking out the trim index of the trigger. I'm not sure if the sram trigger has the same cable pull as short pull shimano triggers, but you could find out elsewhere.

At 44t, both the sram and shimano fd just had a couple of millimeters of clearance to the chain stay, but I have a special geometry with my folding bike.

I don't know if they can clear the 45mm chainline because I have very thick 40mm seat tube and had to 3d print my own braze on adapter. My problem was with getting the fd closer inward.
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