Front derailleur help please

[NHAero]

I have Shimano FD-R440 triple front derailleurs on two of my bikes and on my wife's bike. My newer bike has a brazed-on mounting tab, and the other two bikes are traditional clamp-on set-ups. All are running 9 speed set-ups with Dura Ace 9 speed barcons. On the bike with the mounting tab, the derailleur position needs to be adjusted every 2-3 shifts up or down the cassette when in the middle ring (which is 36T and I think that is the same on all three bikes.) The other two bikes never need correction - there is no chain rub on those derailleurs once the initial position is correct.
Thoughts about how to remedy this on the bike with the chain rub?
Thanks very much

[Cicli]

What bikes?
Some frames with shorter chainstays put the chain at more of an angle range across the cassette. Maybe this?

[cachagua]

I'm going to voice what may be an unpopular opinion here, but I suggest taking some tools to the derailleur cage, to bend it into "tune".

I've done this as standard procedure with derailleur cages of all brands, on all kinds of bikes, from when I started working in shops in the 1970s up to, most recently, a couple of months ago when I set up my newest bike. Judicious re-shaping of the cage yields a derailleur that shifts crisply, never drops the chain, and never needs "trimming".

There are two general shapes you want to aim for, although as usual, the devil is in the details. The cage should be wide at the rear, and narrow considerably toward the front, and it should be wider at its lower edge, right where it comes closest to the big chainring, and get narrower higher up. This is because horizontally, you want more space farther back from the rings. And vertically, you want as much room as practical when the chain is on the big ring, but when the chain's only partly engaged, sitting higher up, you want the cage closer to it so it's guided into engagement. Different cage designs have to be treated differently, and each individual case must be observed carefully and tweaked to its own best performance.

Two caveats: first, some more recent derailleurs seem to have their cage made out of ridiculously brittle metal. I shattered two brand-new FD-7700s trying to tune them, and replaced them with a 7410, which I wailed on mercilessly and now it shifts like a dream. That's consideration #1. The second thing is that trim detents are built into most integrated controls these days, and for God's sake, triple shifters even have indexing. Because your shifter knows where your middle ring is better than you know yourself, presumably? So if you're using a shifter that doesn't allow a pure, uninterrupted friction function across its whole range, you may find the process above considerably complicated. (Dura Ace 9spd barcons are friction or "light action", aren't they? So you should have no problem with those.) At any rate, you should at the very least be able to get the cage to clear on the big ring, no matter the cog you're on, and to never either hesitate nor overshift when going to the big ring.

Worst case, you weed out all the cheezy, cheap pot-metal front derailleur cages from your stable. Who wants to ride tinfoil?! And naturally, I don't recommend this method with non-metallic cages. Who wants to-- okay, we'd better not go there.

[oliver1850]

Any chance your derailleur is angled on the problem bike? It can be hard to get the FD aligned correctly with some braze-on tabs. I've had to file some tabs to get the FD where I want it.

[NHAero]

All three bikes have fairly long chainstays and all are using the same Phil Wood BB and old Sugino AT triple cranks (all driven by preference for a narrow Q factor).
I need to try to measure accurately the cage angle relative to the chainrings, and perhaps the distance from the centerline of the seat tube to the middle ring to see if that is different.

[NHAero]

I took the bike to a shop and they had an interesting comment. They noted that I had a non-typical set-up - not a standard Shimano with specific chainring sizes, and they said that even though my tooth differential is 14T (50-36) that is not the same radial differential measurement as a 53-39 standard Shimano set-up - and he measured mine at 33mm and the Shimano at 29mm. So he thinks the derailleur would work better on a stock set of rings, and one way to mimic that is to slightly downsize the 50 to a 48. The other bikes that have the same FD are both 48-36.
Reactions? Thanks

[oliver1850]

I can't see how changing the big ring is going to affect how often you need to trim while running in the middle ring. You should be able to lower the FD slightly if you switch to a 48, but it's hard to envision that helping the problem.

[Ed-B]

Agreed. It's hard to imagine how dropping the size of the big ring by two teeth could effect the need to trim the middle ring across the gear range...

I think I'd swap out the front derailleur before I messed with the chainrings. If you have the gear ratios that you want, then see if you can make them work. An older mtb front derailleur might fix this.

Such is the challenge of custom drivetrains.

If you can't sort this out for yourself then you need to find a bike shop with a mechanic who's done this kind of thing (many times) before.

[Peter P.]

I'm under the impression all three bikes have the SAME chainring numbers and all three bikes have the SAME front derailleur AND the same, friction 9 speed barcons. Yet one front derailleur needs frequent trimming.

Switch derailleurs between the bad bike and a working bike and report back.

[Ed-B]

The problematic bike is the only one with a braze-on fd, per the first post.

[ultraman6970]

A detail... back in the day up to 7 speed, not idea if this can be applied to 8 and 10... but in shimano you needed to put the FD tad in an angle to help the chain rubbing. After 7 speed i lost any trace of shimano ok?

[NHAero]

The problem bike has these differences (you folks are helping me to think more clearly about this, thanks):

50T large ring instead of 48T
135mm rear hub instead of 130mm, so chainline is out 2.5mm more.
Tab mount FD instead clamp mount

I do think swapping the derailleur is where I am headed. Yesterday the shop folks tweaked the FD cage some, and on the stand it wasn't looking as though it helped.

I'm under the impression all three bikes have the SAME chainring numbers and all three bikes have the SAME front derailleur AND the same, friction 9 speed barcons. Yet one front derailleur needs frequent trimming.

Switch derailleurs between the bad bike and a working bike and report back.

[Ed-B]

We take these things for granted, but it's probably worth asking if anyone ever checked to see if the chainring was spinning true. Because that would certainly cause a rub.

Is there any wobble or side to side deviation in the ring when the crank is turned?

If so, is it just one ring or both outer rings?

[oldpotatoe]

I have Shimano FD-R440 triple front derailleurs on two of my bikes and on my wife's bike. My newer bike has a brazed-on mounting tab, and the other two bikes are traditional clamp-on set-ups. All are running 9 speed set-ups with Dura Ace 9 speed barcons. On the bike with the mounting tab, the derailleur position needs to be adjusted every 2-3 shifts up or down the cassette when in the middle ring (which is 36T and I think that is the same on all three bikes.) The other two bikes never need correction - there is no chain rub on those derailleurs once the initial position is correct.
Thoughts about how to remedy this on the bike with the chain rub?
Thanks very much

All same seat tube angle? All same cranks? All same chain?

[NHAero]

It's pretty much coincidence, but my '72 Bob Jackson and the '12 Anderson both have 73 degree seat angles. Both are running the Sugino AT cranks on the PW 125 R+5 BB, and both are running 9 speed SRAM chains. The Anderson has a braze on tab for the FD, and the BJ FD is clamp on. They both have a 36T middle ring and the Anderson has a 50T outer ring, the BJ a 48T. The BJ has a 130mm hub, the Anderson a 135mm. I have some stuff to measure now based on comments and will post once I have that info.

Great questions, thanks


All same seat tube angle? All same cranks? All same chain?

[oldpotatoe]

It's pretty much coincidence, but my '72 Bob Jackson and the '12 Anderson both have 73 degree seat angles. Both are running the Sugino AT cranks on the PW 125 R+5 BB, and both are running 9 speed SRAM chains. The Anderson has a braze on tab for the FD, and the BJ FD is clamp on. They both have a 36T middle ring and the Anderson has a 50T outer ring, the BJ a 48T. The BJ has a 130mm hub, the Anderson a 135mm. I have some stuff to measure now based on comments and will post once I have that info.

Great questions, thanks

Is the angle of the front der in relation to the big chain ring the same? Der not tilted forward or aft, gap between der and chainring not the same? Tilt?

[NHAero]

I'm feeling like a knucklehead now that I see the problem. I mis-remembered the middle ring on the Anderson - I have a 50-34-24 not a 50-36-24 - so a 16T difference. On the other two bikes with the same FD, the triples are 48-36-24 so a 12T difference. That means the radial distance between the big and middle rings differs by about 8mm. On the Anderson, this means that when the chain is on the middle ring, the chain is NOT sitting comfortably within the offset portion of the inner plate of the FD, so it sits within a narrower portion of the derailleur cage and has to be trimmed more often to work.
So - either I go to a 48-36 like the other bikes, or I find a FD that is made to work on a triple with a larger differential between the big and middle rings.
Thanks to all who helped me think this through and I apologize for not looking more carefully at both set-ups before I asked! If you have a suggestion of a FD that is made for a triple with a 14T or 16T difference between the big and middle rings, please let me know (braze-on mount, bottom pull).

[oliver1850]

I don't know what rings the R440 is recommended for. Most Shimano road triple FDs are going to be for either 30/42/52 or 30/39/50 rings. Perhaps an older XT or LX intended for 28/38/48 would work well. Another might be the RSX, which was for 26/36/46. I may have one of those somewhere. Campagnolo Centaur MTB triples could be had with 24/34/48 rings, which is the closest crank I can think of to what you're running.

Do you need the 50 ring? Perhaps a 46 and a cassette with a smaller small cog would give you low and high gears equal to what you have now.

[NHAero]

I think, since I know the FD works well with the 48-36-24 set-up, and the 50-34-24 dates from when I lived in a far hillier place, I am going to switch the Anderson to a 48-36-24 set-up, rather than play front derailleur roulette. 12T difference is going to shift better as well, and I can get a ramped and pinned middle ring, which i don't have now. Tweeks Cycles has the bling-y shiny silver TA Zephyr rings for half of stateside prices.



I don't know what rings the R440 is recommended for. Most Shimano road triple FDs are going to be for either 30/42/52 or 30/39/50 rings. Perhaps an older XT or LX intended for 28/38/48 would work well. Another might be the RSX, which was for 26/36/46. I may have one of those somewhere. Campagnolo Centaur MTB triples could be had with 24/34/48 rings, which is the closest crank I can think of to what you're running.

Do you need the 50 ring? Perhaps a 46 and a cassette with a smaller small cog would give you low and high gears equal to what you have now.

[NHAero]

Closing this one out to say that mounting the new 48-36 rings to replace the 50-34 rings has completely solved this issue. At least once I remembered I also had to lower the front derailleur!

The price of the equipment these days shifting better is the narrow range of acceptable gearing with which it works best. I didn't want to trial and error being able to find a FD that works well with 50-34 and handles the triple - recognizing that 50-34 doubles are common these days.

In the end, this new gearing matches what I have on other bikes, and the new TA rings are also ramped and pinned (and shiny too!)

Thanks to all who contributed their help