bwilli88 

What Front derailleur are people using to run a 1/2 step plus granny. A typical triple FD will have a huffin big derailleur and will rub against the middle ring with a 49-46-30.
Is any one successfully using a double FD to run a half step + granny?
I know that there are FDs specifically for 1/2 step but they are few and far between and expensive.

carbomb

Shimano FD-M700 / first generation Deore XT stag head front derailleur works like a charm.

I actually bought an Austro Daimler that had a half step + granny setup using a Sakae Custom triple crankset and Suntour ARx components (long cage ARx GT rear). The FD touched ever so slightly when the chain was crossed, but I think that was because I went with a 7 speed freewheel and not the 5 speed it was intended for. It was also put on a shorter wheelbase.

I'd default to some sort of mountain bike, triple compatible FD for this. I have an older, basic Shimano Mountain LX FD that I setup horribly (FD positioned WAY too high) and it managed to shift a similar triple setup no problem with no rubbing for years. All my bikes running this gearing have long chainstays so that probably helps avoid rubbing when crossing the chain.

bwilli88 

I am not thinking about chain rub but the derailleur cage rubbing on the chainring.

carbomb

Ahhh, then I totally misunderstood. I suppose I've been more concerned with the cage extending down far enough to avoid the chain resting on the screw that connects the two FD plates while on a silly small/small combination. You can always mount the derailleur higher to avoid hitting the chainrings (I've had little to no problems shifting or throwing the chain when I do this). Wouldn't a standard triple FD work more readily in all cases while a double or half-step specific FD would lack the range in its swing or depth in its cage to get you in and out of the smallest chainring reliably?

verktyg 

There are lot's of derailleurs that will meet your requirements going all the way back the Huret Allvit from the early 60's. Unlike the Allvit read derailleurs, the front ones actually work well!



French touring bikes used double or triple chainrings with granny gears along with 13-26t or 14-26T 5 speed freewheels. The long arm French touring rear derailleurs from that era could wrap up a lot of chain but they couldn't handle freewheels larger than 28T.


Here's my touring bike that I built in 1992. It has 50-46-30T chainrings with a 13-32T 6 speed freewheel. I used a Suntour MTB front derailleur to cover the 1/2 step with a granny gear chainrings.



I built my off road trekking bike in 1992 too. I used a Shimano 105 FD with 46-26T TA chainrings. It worked just OK...



After I ovalized several TA 26T chainrings I switched to a ~1987 Shimano Deore XT 48-38-28T crankset. I went with a ~1987 Shimano Deore XT front derailleur too. It works flawlessly.




Several issues: the seat tube angle can affect the way the front derailleur sits relative to the chainrings. If the the seat tube angle is steep, the cage may not reach down far enough to keep the chain from dragging on the spacer at the bottom of the cage. (see Shimano 105 above)

The second thing, the derailleur cage should have an arc close to the radius of the large chainring. (see Shimano Deore XT above)


It's hard to tell which FD will meet your need without some trial and error. Many of the early Suntour and Shimano MTB FDs were made for triples and will work well.

Look for one with a long cage and a smaller arc.

Here's some Simplex front derailleurs with wide inner cage plates for triples. The last one is currently on eBay:




Shimano early 80's 600 FD:




Campy made some long arm cages in the early 80's too - Victory and Triomphe FDs came in regular and touring style for touring, Campy 980 FDs frequently show up on eBay at reasonable prices.



This should get you started.

verktyg

Chas.

The Golden Boy 

As long as you're getting an FD that can reach low enough for your granny (28-32) and the outer plate can clear your big ring (50-52) you're golden, so to speak...

The old MicroDrive FDs were made to only fit over the circumference of something like a 42-46 big ring, so the arc of the plate wouldn't clear a 48 or 50.

The "for half step gearing" FDs have a little bump on the inner plate, specifically to help the big jump from 28-45 instead of the more normal 28-38 or 40. I think the Bike Recyclery site had some really nice pix of both styles of M700 FDs, both normal and half-step. Otherwise, check the VeloBase pix of both styles.

On my half step bikes, I'm using a Sachs-Huret, a Simplex (stock on 1985 Trek 620 and 720), a Suntour Mountech and a regular Suntour XC Pro. I have used a first generation Suntour Cyclone as well- without the cage extension.

vtchuck

FWIW, I use a Campy NR FD for my 49-39-29 triple. Rated for an 18 T difference, but works at 20 T for me. Should shift the 49-46 well. YMMV

The Golden Boy 

Here's a half step specific, M700 FD, notice the bump on the inner plate:





Here's a regular M700 FD- notice the smooth inner plate:

steelbikeguy

hmmm..... I'm using a regular SunTour Cyclone front derailleur on my half-step-plus-granny. Nothing special about it..



The chainrings are 26-46-49 (unless I'm mis-remembering the size of the granny).

back in the day, I don't recall anyone making any special derailleurs for this purpose. There were some derailleurs with a longer cage to help handle a much wider range of chainrings.

Of course, this all assumes that you are using friction shifting. Fancy derailleur cage designs were invented to help indexed shifting work. If you are trying to use half-step-plus-granny with indexing, then that's a whole different can of worms.

Steve in Peoria

bmthom.gis

I'm using a Shimano LX...with Biopace rings! Shifting is flawless

SkyDog75

My '85 Schwinn Le Tour Luxe was originally equipped with 30/46/50 chainrings and a SunTour Mountech front derailleur.

USAZorro

Wouldn't chain rub against the middle ring while in the granny be dictated more by the chainline than by the FD?

John E

When I converted my 1980 Peugeot PKN-10 from 52-42/14-28 to 48-45-34/13-15-17-19-21-24, the stock Simplex front (and rear short cage) derailleurs worked very well.

carbomb

Not to be argumentative, but I'll reply with "no" I don't see a bump. I think what you're seeing is chain wear and gusset holes for lightening + strength.





Those are more views of the half-step models currently on eBay. It's my understanding the half-step's biggest difference is that it's meant for a larger outer chainring where the original has an arc that would more closely fit a typical, mountain large chainring. I'm going to keep an eye out though for a half-step one so I can do a thorough side by side. I have a hunch in practice it's probably more marketing than necessary nuance.

The Golden Boy 

You're correct- I was seeing the chain wear on the leading and trailing edge of the plate and assumed it was a sculpted plate.

So here's me "remembering" seeing all these sculpted plates- and none of the units I remember having them- have them.

Without having a side by side comparison, there's just pix and other people's reports:

https://www.bikeforums.net/classic-vi...content-2.html

Vintage_Cyclist

SunTour XC Sport on 52-42-26 front, 14x32 rear.



Shimano Deore LX on 52-42-34 front, 14x28 rear.



Both working smooth as butter.

old's'cool

Mid-late 80s Shimano 600 works a treat!

Conrad990

I'm using a Huret Success front mech with Stronglight 45,42,28 rings. Don't buy new ones, they're too faddy, ramps, dropped shaped inner plates etc. Old Suntour vx, cyclone, or similar basic road mechs work best. It's sometimes slow and tricky getting up from the granny to middle but I'm not in a hurry at the top of the hill😉

John E

Good point regarding newer rings and cranksets, which are often not designed for half-step or half-step-plus-granny.

JohnDThompson 

I've used Campagnolo Record, Zeus Criterium and Gran Sport, SunTour Cyclone, Dura-Ace, and maybe a couple others on half-step + granny setups without problems. The only potential issue is that with too big a difference between the large ring and the granny, the chain can drag on the bottom of the derailleur cage in some of the gear combinations using the granny. The ones I mentioned above worked fine with 50T large ring and 26T granny.

davester

I switched my all Campy NR Cooper over to a triple (52-42-30) and was sure that I would need a new derailleur. However, The standard NR double FD works just fine. My advice is to just go with what you've got unless you find that it won't work.

bwilli88 

Since this was dredged up from last year, I went with a Shimano 105 10 speed triple that I ground off the bottom edge of the rear part of the chain guide of the front derailleur.

You can see that the back side of the FD would have hit the middle ring because it is much larger than a typical mid ring.

GAJett

Limited experience but I have had unqualified success with:
SunTour Cyclone, Superb,& Superb Pro; and
Heuret Jubalee.
All have worked on a 49-46-26.
The Superb Pro on a 44-41-24.

Recently put a Shimano CX70 on the first above, but the inner plate rubs the middle ring when the proper vertical of 1 to 3 mm is made. It's probably now set at about 8 to 10 mm to clear. I will need to modify the inner plate to get a proper fit.

Would like to try a Campy NR sometime.

Not really sure if any current racing doubles have a range for triples anymore. Seems like the industry (Shimano at the front) increasingly designs for single-purpose use and what they think is needed, rather than flexibility, general use, and what independent thinkers need.

old's'cool

I concur on the Suntour Cyclone and Campy NR. Also having success with Shimano Altus.

ThermionicScott 

Always good to hear the rest of the story, @bwilli88. Dig the custom shaping to make it work.