Compact double front derailleur

[Arbito]

Wondering if anybody has advice on front derailleur choice for 46/30 crankset. I’m going with an microshift advent 9 speed Cassette and their front derailleur looks great! But my seat tube is 28.6 and I‘d need a shim. I’m worried it’ll throw the geometry off. I’m using downtube friction shifters so maybe it’s a moot point. I noticed IRD has a sub c derailleur that looks nice, but I’d need to purchase their braze on clamp, about $50 more than the microshift. Anybody had any good luck with either items... or?

[Alex I]

I run a Shimano FD-CX70 using a 44/28 crank. I use it with brifters so I imagine it’d work fine with friction as well. Note that it comes in bottom pull (typical road) and top pull (some cyclocross) so choose wisely. Came in several clamp diameters. Also it was recommended on another forum to use with a 10s chain since it’s a 10s FD (with the comment that the wider 9s chain would rub too much). I never tried with a 9s chain. Worked for me, YMMV

Alex in CO

[Steve Palincsar]

On 7/20/20 12:59 AM, Arbito wrote:
> Wondering if anybody has advice on front derailleur choice for 46/30
> crankset. I’m going with an microshift advent 9 speed Cassette and
> their front derailleur looks great! But my seat tube is 28.6 and I‘d
> need a shim. I’m worried it’ll throw the geometry off.

Using a shim with a front derailleur does not throw the geometry off.


--
Steve Palincsar
Alexandria, Virginia
USA

[Mike Hammer]

I tried a CX70 with 34-48, friction shifting, 28.6 downtube (with shim) bottom pull and 9 speed.  Shifted fine but required lots of trimming (about every 3 cogs) which I assumed was due to the wider 9 speed chain.  I now have an Ultegra FD-6401 from the 8 speed (?) era that shifts as well as the CX70 and I do not have to trim over the full cassette on the big ring.  I have not done anything special with chainline, it just works.  This is on a Black Mountain Road+.  

[Evan Estern]

I like the Suntour Cyclone ll.   They are usually available NOS on eBay for less than a modern FD.  They are specced as having an 18 tooth range.  I have them on two bikes, a Norther Lyon with 10 speed cassette and 46/28 chain rings and a Rawland Stag with 9 speed 44/28.  If properly adjusted there is no need to trim except for the small/small combination which is unlikely to ever get used.  They shift beautifully and are lightweight and reliable.  No shim required for 28.6 seat tube. 

[Jim Sikking]

+1 on Evan's comment. I've used the Cyclone II with up to a 20 tooth difference in front.

I also like the Shimano 600EX (6207) which is similar in design.

Jim

San Antonio, TX usa

[Arbito]

Thank you very much. Lots of info to research here!

[David Cummings]

When this question comes up, it seems that flat-caged FD’s get mentioned repeatedly for situations like this. Most of Suntour’s FD’s were designed as such. They also handled half-step+granny setups very well: 50/45/26 or 24. That’s a 19t-21t gap. My Mountech can (delicately) handle a 50/26.

David “Mind the gap!” In MT

[Bill M.]

Every standard road FD I have tried has worked fine with 46/30 rings as long as the frame allows it to be lowered appropriately.  Smaller rings that that have sent me to a mountain bike FD.

Bill

Stockton, CA

[Michael Mann]

I LOVE the look and performance of older XT (and identical but for label) LX front derailleurs and have them on most of my bikes. I also run a White Industries 26/42 crankset with an Ultegra FD with zero issues.

Mike M

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[Benz Ouyang]

On Sunday, July 19, 2020 at 11:48:10 PM UTC-7, Arbito wrote:

Wondering if anybody has advice on front derailleur choice for 46/30 crankset. I’m going with an microshift advent 9 speed Cassette and their front derailleur looks great! But my seat tube is 28.6 and I‘d need a shim. I’m worried it’ll throw the geometry off. I’m using downtube friction shifters so maybe it’s a moot point. I noticed IRD has a sub c derailleur that looks nice, but I’d need to purchase their braze on clamp, about $50 more than the microshift. Anybody had any good luck with either items... or?

1. Using a shim will not throw the geometry of the front derailleur off. It may look ugly if it's shimmed down from 34.9mm though.
   
2. Since you're using friction, you can consider a Campagnolo CT front derailleur. I have that working with a White Industries 46/30 VBC crank. The good thing about Campagnolo front derailleurs is you can either use a 28.6mm clamp with a braze-on version, or actually switch out any other clamp size for a proper 28.6mm version for a cleaner look, because Campagnolo CT front derailleurs all have interchangeable clamps. In other words, the cage components are the same, so you just need to track down a 28.6mm clamp body.
3. I've also used a Shimano FD-CX70 down to a 42/28 crank. This may provide more flexibility in case you want to go down to smaller chainrings as the Campagnolo CT is close to its limit (without the cage hitting the right chainstay). The FD-CX70 is also a close visual match for a XTR rear derailleur from the M960 series (shiny dark grey), if that's a concern.

[franklyn]

I have three bikes with 46/30 cranks and I agree with the observations stated here that flat cage front derailleurs do the job well. My favorite has been shimano FD-7400 series, and I also have success with FD-6400 series. 

Franklyn

On Sunday, July 19, 2020 at 11:48:10 PM UTC-7, Arbito wrote:

[jeffre...@gmail.com]

My wife and I currently run 2 bikes with 46/30 combos and 1 bike with a 42/26 combo (Gravel/Dirt Bike).  All three run IRD Sub-C front derailleurs.  Works as designed:

https://www.interlocracing.com/shop/product/60110-ird-front-derailleur-sub-c-braze-on-2351?search=derailleur 

The small compact cage allows it to be installed pretty low on the seat tube without interfering with the right chainstay (some front derailleurs have that problem).

Good luck!

Jeff 

[Floyd Tiny]

This is my experience. I have several bikes with similar chainring combinations (44/30, 42/30 etc...). Ebay is full of older, cheap, simple front derailleurs that should work fine for you. I'm using old (70s-80s) Campagnolo Record on two of them and an old M732 Deore XT on another. I'm building one right now and will either put another old Campagnolo one on or a Suntour...  

I should also mention that these are all on indexed (Campagnolo, SRAM, Shimano) drivetrains- yet the old derailleurs work very well.

Best of luck-

FB in NY

[Justin, Oakland]

I use a 11 speed SRAM front derailleur attached to braze in adapter. Works fine with 46-30

Also use a CX70 with a shim for 42-30 and it works fine.

[Arvi, Oakland]

Piling on another answer. I've had good results shifting subcompact cranks with both 6800 ultegra + STI shifters and DA 7800 + downtube shifters. I wouldn't bother w a sub-compact specific FD, unless I didn't have something else on hand.

[satanas]

Personally, I'd avoid the Ultegra 6400 FDs and the equivalent 105s as well; I've had multiples of both crack through the top corners of the cages; I've never had any other FDs do this. Dura-Ace 740x shift better and do not crack, ditto for CX70, etc.

Most road FDs should be fine with 46x30 provided the seat angle and BB drop aren't such that the tail of the cage hits the chainstay before they can be set low enough. Post-STI designs tend to be more rigid and to shift better IME, in part due to improved cage shaping. It also pays to try to match cage width and chain width; if the mismatch is too great either way you can get poor shifting or excessive rubbing - as you can with poor setup.

Later,
Stephen

[Mike Hammer]

The Ultegra 6400 and equivalent 105 have a sort of diagonal arrangement of the cages and linkages.  The Ultegra 6401 has the straight/more rectilinear arrangement.  The difference is obvious when you see them together.  I have had a 6401 on a RB-1 since 1993 with no problems.  But, I don't do the kind of miles you guys do.  

[satanas]

^ The 6401 FD is basically similar to the 740x STI equivalent. These are fine, but IME the earlier 6400 style FDs with the "diagonal linkage" described above crack frequently through the upper inside bend of the cage (next to the parallelogram arms). The similar 105 mechs failed this way too. I've personally had both models crack there, after which the FD geometry and rigidity is off and they shift poorly; we replaced several of these in the shop back in the day. While you can try to bend them back, once the cage is cracked this is a lost cause IME, and I wouldn't use these without carefully inspecting the cage for hairline cracks on a regular basis. However, IMHO it's easier just to avoid these and use something else.

Later,
Stephen

[Tim Evans]

CX70 with a 46/30 and a 6 speed cluster using an 8 speed chain required trimming every 3 cogs.  A new Shimano FD-2400 2x8-Speed Claris, still available new at bike shops for $20, works great.

Tim in So Cal

On Sunday, July 19, 2020 at 11:48:10 PM UTC-7, Arbito wrote:

[Tim Quinlan]

On Monday, July 20, 2020 at 11:11:37 AM UTC-4, Bill M. wrote: 

Every standard road FD I have tried has worked fine with 46/30 rings as long as the frame allows it to be lowered appropriately.  Smaller rings that that have sent me to a mountain bike FD.

Bill

Stockton, CA

This has been my experience as well.

Tim, Pittsburgh, PA, USA