Derailleur Hangers Demystified (2024)

Derailleur Hangers Demystified

4/2/2014

26 Comments

As long as there are no seriously rusted or seized components to deal with, the “front end” of a triple-crank conversion is pretty straightforward: Remove the crankarms, unscrew the bottom bracket lockring and adjustable cup, slide out the original spindle, and replace it with a longer one of the correct size. Grease the bearings, reassemble and adjust, bolt the triple cranks to the spindle, and you’re done. (The procedure is the same whether you’re installing a conventional triple crankset or a double crankthat’s been converted to a triple with a triplizer ring and attached granny ring.)

The originalSimplex rear derailleur on this mid-1970s Raleigh was later upgraded to a better-shifting Suntour derailleur of about the same vintage. The changeover was simplified by Raleigh's penny-pinching--but ultimatelyhelpful--decision to outfit the frame with a mounting claw instead of a brazed-on hanger.

But the “back end” ofa tripleconversion—which ordinarily involves replacingan existingmid- orshort-cage derailleur with a long-cage model capable of handling the wider-range gearing of the triple—has some potentially confusing variables that I'll make a plucky effort toclarify here.

Integral Mounts vs. Mounting Claws

Thegood news is thatif you’re working on a relatively recent bike and components—anything after the late 1980s, say—you can bolt pretty much any derailleur onto any frame, because the interface between them has been almost entirely standard since then.

But of course, most readers of this blog will be retro-grouch types who are likely to be dealing with older equipment. In the 1960s, 70s, and on into the early 80s, the standardization we see today hadn’t yet taken hold, and there were at least three competing systems for mounting rear derailleurs. Each was promoted by a component manufacturer who hoped to lock in future derailleur sales by selling frame makers and the bicycle-buying public on the virtues, if any, of its own proprietary approach.

All three mounting systems were available in two variants:In anintegral mount—sometimes called a braze-on mount—the tabthat supports the derailleur isa permanent part of the bike’s frame. In bikes that use a mounting claw, the derailleur itself is bolted to one end of a shaped metal plate—the mounting claw—that is itself bolted to the frame at the other end.

Above, an integral--but not original--derailleur hanger on a Gitane Tour de France. The stock Simplexderailleur was originallyfastened to the plain dropout with a mounting claw. The brazed-onCampagnolo hangerseen here was later added by a frame shop before a since-regretted repaint.

Below, the previouslypictured Raleigh with the derailleur removed to better show the claw. The bolt to the left of the axle slot is threaded into a specially shaped nut that engages the rear half of the slot.

In the 1950s and 60s, the mounting-claw system was widely used on bikes of all quality levels. But as time passed, bike manufacturers moved toward integral mounts, beginning with their higher-priced models, and by the mid-to-late 70s, the use of mounting claws was pretty much limited to entry-level and department-store bikes. Thatmay bewhy somany people look downtheir noses atthem today.

But despite theirundeservedly lowbrowimage, claw mounts have some real advantages. Since they’re not part of the frame itself, a claw that gets twisted out of shape when the derailleur gets tangled up in the spokes can easily be replaced at low cost (don’t ask me how I know this). The same sort of mishap on a bike with an integral hanger would require having a frame builder cut off the damaged piece, braze on a new one, and repaint or rechromethe affected area.

As an added plus, the hardware that fastens the mounting claw to the to the dropout is generic, so a claw made for one company’s derailleur cantypically be exchanged for a mount of another style without a lot of head-scratching.

Above left, a Campagnolo-type mounting claw, turned over to show the special-purpose nut that engages the axle slot.To itsright, a Huret mounting claw (The nut and bolt are interchangeable and work for either style claw).

Campagnolo-Type Mounts
Developed by Campagnolo for its own product line, this type of mount is easily recognized by its 10 mm threaded center hole and a characteristic notch at the seven-o’clock position, which engages the derailleur’s B-limit screw for fine-tuning of its rotational position.Integral Campagnolo hangerswere used on a great many Italian bikes, as well as those high-end French ones—like the Gitane Super Corsa—that were originally equipped with Campagnolo derailleurs.

This system has since become the de facto world standard. If your old ride is set up this way, it will (with a few exceptions) accept any non-French derailleur manufactured from 1960 or so to the present. Everyone should be so lucky.

Simplex Mounts
Campagnolo’s chief competitor was Simplex, a French company that went its own way with product design. Simplex mounts are recognized by their more rounded shape and the absence of threading in the mounting hole, since their mounting bolts—unlike Campagnolo’s, which screwed directly into the claw or hanger—passed all the way through the mount and were secured on the inside with a nut. (Some Simplex derailleurs were fastened with a shoulder bolt that was inserted from the back of the dropout and threaded into the derailleur).There are a couple of other oddities to the Simplex mounting system. Although a Campagnolo-type derailleur can't be mounted directly on an unmodified Simplex mount (more about this in a moment), a non-claw-type Simplex derailleur can be bolted directly onto a Campagnolo mount. This canseem slightly strange, since it involves passing a 9-mm bolt through a 10-mm threaded hole.Inpractice it works okay, although few people seem interested in thisparticular component combination these days.

The second oddity is thatalthough Simplex mounting clawsare bolted to the dropoutwith the same generic hardware used for Campagnolo claws, theclaws themselves are somewhat model-specific. In other words, there's nouniversal Simplex claw thatwill accept any Simplex derailleur. You need to have thecorrect claw (and the correct derailleur-to-clawmounting bolt) for the particular derailleur you plan to use.

To make matters worse, there seems to be no product marking or numbering system that makes it possible to tell which hanger goes with which derailleur.And somepeople claim that French bikes are difficult to work on!

In any event, new derailleurs designed for the Simplex mount haven’t been made for decades. Used examples are fairly easy to come by,but pose problems of their own:Simplex derailleurs were typicallymade almost entirely from Delrin plastic,which was reasonably tough when new, but now, forty years later, tends to break with discouraging ease.Worse yet--at least from the standpoint of the recreational cyclist,Simplex catered mostly to racers or would-be racers, somost of the derailleurs it did make were short-cage models.In the late 70s and into the 80s—near the end of its corporate life—the company did make a few long-cage models. These turn up on ebay from time to time, but they’re scarce and tend to command high prices.

Above: A Simplex dropout with the original, unmolested integral derailleur hanger. Note theunthreadedbolt hole and the absence of any stops or notches, in contrast to the Campagnolo and Huret mounts pictured earlier.Below: A Simplex hanger--originally similar to the one above--that's been "butchered" to accept a Campagnolo derailleur. The mounting hole has been threaded and a notch has been cut with a file to act as a derailleur stop.(The chainring bolt in thedropout slot has no bearing on the derailleur mount--it's there to serve as a stop for positioning the rear wheel.)Photo courtesy of H. Vanneck.

So what do you do if you have an original 1960s or 70s frame—maybe a nice Peugeot PX-10—that you want to retrofit with a long-cage derailleur for use with a triple crank? You have at least five options,including a couple of good ones.

The Brutalist Approach: Cut off the Simplex hanger with a hacksaw, then use a file to clean up the cut area, shaping it to match the non-drive side of the rear dropout. Paint or grease the cut and filed surface to prevent rust, bolt on a Campagnolo mounting claw and the long-cage derailleur of your choice, and you’re in business. If done carefully, the result can be hard to tell from a dropout that was manufactured without an integral hanger to begin with. Done crudely, it looks like hell.

Pros: Cheap and effective.

Cons: Widely regarded as acrime against humanity. It may also reduce the bike’s resale value, if that matters to you.

The Modified Brutalist Approach: Bring bike to a good frame shop and have the Simplex hanger cut off and a standard hanger brazed on in its place.

Pros: Difficult to tell from original if done by a skilled professional.

Cons: Costly, since the frame will have to be at least partially re-chromed or repainted where finish is damaged by brazing heat.

The Hybrid Approach: An integral Simplex hanger can be modified to accept Campagnolo-style derailleurs by running a 10 mm tap through the unthreaded bolt hole and filing (or grinding, but be careful) a stop in the body of the hanger, using an existing Campagnolo hanger as a pattern. Again, paint or grease disturbed original paint or chrome to prevent rust.

Pros: Invisible when derailleur is installed. Modified hanger will accept Simplex as well as Campagnolo-type derailleurs.

Cons: May reduce frame’s collector value.Scorned by Francophiles.

The Purist Approach:

Track down a functioninglong-cage Simplex derailleur (be aware that this may cost beaucoup d'argent), and install it on the unmodified hanger. (Several vintage non-Simplex derailleurs are also said to be compatible with Simplex hangers that have hada 10-mm tap run through their original 9 mm bolt holes. This will at least spare you the stigma of grinding a stop into the hanger as well. Among these arethe Shimano Crane, the Schwinn Le Tour—which was also manufactured by Shimano—and the first-generation Campagnolo Rally. There may be others as well. I have no first-hand experience with any of these, so don’t ask me.)

Pros: No criticism of the puristapproach is possible.

Cons: Expensive; limited derailleur options.

The Hermaphrodite Approach: Leave the integral Simplex mount alone, and mount a standard derailleur clawon the dropout in the usual manner/

This sometimes takes a little fiddling. Some claws have a sort of S-shape when viewed edge-on, allowing the derailleur to sit a little closer to the freewheel than it otherwise would. But this can causeinterference between the claw and the integral hanger. A flat mounting claw will usually avoid this problem, butif the derailleur mounting bolt is long enough to protrude through the back of the claw, it may bear against the integral mount beneath and make it impossible to tighten the bolt all the way. This can be addressed by switching to a derailleur with a shorter bolt, or grinding or filing the end of the bolt enough to eliminate any interference. Adding a washer between derailleur and claw may also work, although this will sometimes move the derailleurfar enoughoutward that it will lack enough travel to shift onto thelargest freewheelcogs.

Pros: Cheap and fast; leaves integral hanger intact for the benefit of generations as yet unborn.

Cons: Presence of both integral hanger and claw is not noticeable unless you look closely, but theknowledge that both arethere maylead to persistent low-grade angst on the part of some riders.

Below, a Campagnolo mounting claw attached to a frame alreadyoutfitted with an integralSimplex hanger. The resulting assembly looks a little strange before the derailleur has been installed,but it'sscarcely noticeable afterwards.Note that the length of the derailleur mounting bolt can't exceed the thickness of the claw,or it will press against the integral hanger behind the mounting hole and prevent it from tightening all the way.

Huret Mounts
Huret, anotherbygone French component manufacturer, also had its own proprietary derailleur mount. As you can see in the photos above, it's superficially closer in appearance to the Campagnolo hanger than the Simplex version. The threaded mounting hole accepts a standard 10 mm bolt, but the notch that serves as a stop is located at about four o’clock, rather than seven o'clock.

A Campagnolo-type derailleur will thread right on to a Huret mount, butwill likely sit at a crazy angle relativeto the chainstay. The derailleur may even function in this position, more or less, but shifting performance is likely to be lousy.

A Huret hanger can’t be modified to accept standard derailleur by filing or grinding it, as a Simplex hanger can. That leaves you with the choice of cutting it off and using a claw (the Brutalist option), having a frame builder braze on a new one (the Modified Brutalist option), or using the Hermaphrodite approach of keeping the original brazed-on mount while adding a mounting claw.

The Purist approach—finding a Huret-compatible derailleur—can also work, but be aware that just because a derailleur was manufactured by Huret doesn’t necessarily mean that it was designed for the Huret mounting system. The company also made derailleurs for the Campagnolo-style mount. Some models were convertible from one to the other by using special tabbed washers, which came in two different versions. Good luck.

26 Comments

Jeremy

2/2/2015 12:18:37 pm

Hi Jon! I just happened to be searching for info about derailleur claws and Google recommended the Red Clover site! My question is a silly one, but is about something I've never done it before: Can I use a clawed derailleur on an integral mount hanger (after removing the claw of course)? I'm 99% sure the answer is "sure you can," minus perhaps a few rare exceptions. Anyhow thanks for the informative article. Jeremy

Jon Varalink

2/3/2015 12:21:54 am

Your guess is about right--derailleurs made after 1970 or so, when integral derailleur hangers became common, were designed to be used interchangeably with a claw mount or an integral hanger. Note that the integral hanger has to be compatible with the derailleur, though--a derailleur designed to work with a Huret-style mounting claw, for example, will call for a Huret integral mount.

Mark "gugie" Guglielmana

4/29/2015 07:49:41 am

Now I know where you're coming re:claws!

As a counterpoint: https://www.flickr.com/photos/49353569@N00/12748009134/

Joe Morris

9/29/2015 12:51:56 pm

Instead of having to install a full claw for a Huret you can also just put in a stainless washer that you've drilled and notched, and bent in slightly so the B-screw hits it. Here's a picture: https://xenotropic.net/bikes/IMAG0160.jpg.

Steve Boos

4/9/2016 07:36:20 am

I'm working out how to fit a long cage Suntour Cyclone RD to a frame with a Simplex hanger. I'm interested in your solution, but was wondering whether you have another image of the washer showing how you modified it. Also, how do you prevent the washer from moving?

Jon Varalink

4/9/2016 09:33:04 am

Hi Steve,

Alas, the modified washer technique only works if you're mounting a Campagnolo-style derailleur on a Huret mount, not a Simplex mount. In order to use the Suntour derailleur, you would have to tap the original 9 mm hole in the Simplex mount for a 10mm x 1 bolt, and file a notch in the hanger.
That's often done, but I really don't like filing hangers. But if you can get a long-cage Shimano Crane or Schwinn Le Tour rear derailleur (they're the same; the Schwinn version is just branded differently) you can just tap the hole and mount the derailleur without any need to file a notch.
The actual tapping is very easy--just takes a 10 mm tap, a tap handle (available pretty cheaply from any good hardware store) and the derailleur. Long-cage Cranes and Le Tours are not hard to find on ebay.
Or you could install a long-cage Simplex--something like an SX-410--without any need to modify the hanger at all.

Al Hodkinson

10/1/2015 08:13:17 am

This is really useful information, thank you!

Bob Gomon

10/20/2016 06:07:00 pm

There there is something else on the market that changes your French drop out derailleur attachment options completely. I have a late 70s Gitane with Huret rear drop outs and I have recently added a Wolf Tooth Road Link to the bike. This is a CNC compoenent that allows you to use any "Campy" style rear derailleur. It also lengthens the drop out hanger distance, increasing the size of the largest cog the derailleur will accomadate. These are readily available on eBay for less than 30 dollars.

For pictures and modern application see the article about "Turkey Vulture Gearing" on the http://gravelandgrind.com/turkey-vulture-gearing/ web site. I am riding a Stronglight 99 triple with a 50/40/28 chain rings, a 32-13 freewheel and a Shimano "Deerhead" M700 derailleur using the Wolf Tooth and it works great. Happy to supply pictures if that would be helpful.

Gregory Wilson

6/3/2019 01:28:41 pm

Id love to see pictures of this Bob!

Paul W.

11/19/2016 11:51:28 am

What is to be done if there is no hole to the left of the dropout slot to bolt the claw to the frame? My 1950's Grubb has no such hole.

Michael Larmer

12/2/2016 11:02:26 am

http://www.dhresource.com/albu_1110813825_00-1.0x0/10pcs-lot-for-shimano-rear-gear-mech-derailleur.jpg

That little machine screw that looks like it goes into a hole in the frame actually goes into a special fitting that slides into the back of the dropout.

Jon Varalink

12/2/2016 01:25:07 pm

Michael Larmer speaks the truth. The hanger doesn't bolt to a hole in the dropout--it bolts to the slot. Basically, the claw goes on the outside of the dropout, and is ordinarily positioned in the slot by a couple of little raised bumps--or sometimes a narrow crescent-shaped ridge--that engage the slot from the front. (You can see this feature of the claw in the photo that shows the two different claws--a Campagnolo and the Huret--one from the front and one from the back).

The little mounting bolt that comes with the claw goes through the hole in the claw and through the slot, with the bolt head on the outside. On the inside of the slot, instead of a conventional nut, the mounting bolt is secured with a specially-shaped nut that has a ridge in it that's designed to just fit in the slot. Since you can't turn the nut itself (the ridge locks it into the dropout slot) you tighten the mounting bolt from the head end, first making sure that the claw/nut/bolt assembly is slide as far to the back of the dropout as it will go. When you're done, the claw fills about half of the slot, but you have the front half open to accept the axle of the hub. A little blue Loctite on the nut will help keep the assembly from working loose.

All of that looks complicated written down, but when you're looking at the rear dropout with the mounting claw in hand, it will all become obvious, I promise.

Paul W.

12/3/2016 09:56:38 am

Thanks, Michael and Jon. I appreciate you explaining this. I bolted my derailleur right up! (blushes)
The hole that I had seen on some classic dropouts, to the rear of the dropout slot, must have just been a mudguard bolt hole.

Steve Barner

3/10/2024 09:24:53 am

Replying to a very old thread, but some French dropouts did have a hole in line with the axle slot. This was for a plastic plug. To cut manufacturing costs, instead of threading a long hole through the back of the dropout and installing a threaded adjuster with a spring to hold it in place, a non-threaded hole would be drilled, the adjuster slid through, then threaded through a hole in the plastic plug. The plastic would keep the adjuster from turning on its own. An even less expensive approach was to do away with the hole and use a half-moon shaped plastic piece within the dropout slot. You could use the same basic dropout on less expensive bikes by just leaving off the adjuster.

Dan

1/10/2017 01:53:58 pm

I'm possibly buying a 1974 Raleigh Super Tourer this week that appears to be in pretty good condition - but am concerned with the difficulty upgrading the components on it should they be beyond using. Will I easily be able to put a modern 3 or 5 speed freewheel or cassette and a derailleur on it with a single chainring up front? From this post it seems like it would be hard because of the Huret dropouts supposedly on it?

Chris

8/10/2018 02:10:18 am

Hi Jon,

I have a hanger which somehow is similar to the two b-screw tips Huret hanger adapter but the tips are rotated slightly.

A picture can be seen here: https://www.rennrad-news.de/forum/attachments/schaltauge_1-7-jpg.586443/

Nechs which do not fit: all with B-screws (or angle adjustment screws), also modern Campys without the screw do not fit. The mid-80ies Sachs Huret New Success Touring mech (http://velobase.com/ViewComponent.aspx?ID=D8601937-0FD6-48D8-8DC4-CF98D64B2861&Enum=108&AbsPos=6) does NOT fit.

BUT: the later ARIS fits (http://velobase.com/ViewComponent.aspx?ID=B4AB4327-B334-4DFB-A60B-ED9C6BE75CF7&Enum=108&AbsPos=10)

Any idea what that hanger is made for??? It is on a mid-80ies rando with narrow cantis (55mm), Columbus Cromor tubing, no manufacturer labels, no marks/ stamps on the dropouts (front dropouts are Gipiemme).

Cheers,
Chris

Chris

8/10/2018 03:20:22 am

OK, 1 hour of Google search later I know it is a Shimano UF Dura Ace semi-vertical dropout. But this does not solve my problem that no average derailleur fits..

7/26/2020 09:21:50 am

I'm facing this issue trying to mount a Suntour ARX on a 73 Raleigh Competition with Huret dropouts. All is good except the nub for the B-limit screw has no place to hit. I'm eyeing a tube of JB Kwik weld with the idea of putting a blob on the hanger where the nub would be for a Campy. It could always be filed off in the future if needed. I wonder if anyone has tried this? Otherwise, the tweaked up washer like Joe Morris described sounds promising.

Brittany Day link

12/23/2020 08:20:27 am

Thank yyou for being you

George Otis

6/27/2021 09:47:52 pm

I have a 1968 Lejeune frame with Campagnolo dropouts, that I wish to set up with all-French components. The Simplex Criterium 637 derailleur mounts on the dropout fine, but sits at a bizarre angle, actually facing a bit backward at about a 7 o'clock position. Needless to say, it basically won't shift anything this way. The derailleur is in good condition (I mounted an identical NOS example and it sits and behaves the same way). I have heard you can adjust the upper pivot tension on these derailleurs, but I don't see any obvious way to do that, and I'm not sure it would make any difference. Any suggestions? I prefer to avoid altering the dropout.
BTW, I have used a later Simplex RD (SX410GT) on a 72 Motobecane Le Champion with a Campy dropout. It sits angled pretty far forward, about 4 o'clock, but shifts quite well.

William Smith

7/30/2022 04:15:09 am

I heard a story about the mounting hole in rear dropouts for Campagnolo derailleurs. Apparently, in older models, this is a compound thread - metric diameter and pitch in threads per inch. The reason for this, apparently, is that, after the Second World War, the United States sent Italy a large consignment of machine tools to help them get their industry back up and running. You American chaps, quite rightly, prefer to use Imperial measurements, so the screw-cutting lathes were geared to produce inch-pitch threads, which the Italians had to settle for, although they used metric diameters. I think Campagnolo has now adopted an all-metric thread for derailleur attachment. I had new dropouts fitted to an old Bob Jackson, and discovered that the mounting bolt for the Gran Sport derailleur started to go in, but fouled after a few turns, suggesting a different thread pitch. I had to buy a new derailleur, which mounted without any trouble.

Jon Varalink

8/10/2022 11:28:47 am

Hi William,

I had not heard that story before, but it sounds plausible to me. What derailleur are you using now?

Steve Barner

3/10/2024 09:47:42 am

Late to the party, but it's interesting to read this, as it has long been my belief that this was the story behind the Italian metric-diameter / inch-based thread pitch combination. I knew that the US had shipped huge quantities of surplus machine tools to Europe after WW2 to help rebuild economies that had been bombed to oblivion. This rebuilding effort was a stroke of genius as it not only addressed many of the issues that lead to popular unrest in a vanquished population, but it got the surplus equipment out of the US, leaving our machine tool industry largely intact. Surplus equipment available at bargain prices is one of the factors that leads to economic downturns that typically follow any major war.

Some machine tools can be converted to cutting metric thread pitches by changing gears, but often it involves cutting new lead screws, and that can be a difficult job. It is entirely believable that the Italians took the most expedient approach and just stuck with what could be put into production right away. Italian threads of this era also have a different profile, and use a 55 degree thread angle, but this typically doesn't keep it from being interchangeable with British threads of the same diameter and thread pitch. While the French threading is generally looked at with disdain today, it can be argued that is only because the rest of the world wasn't forward thinking enough to embrace and adopt it, as it is the only completely metric solution. Add in the "Swiss" left-threaded fixed cup solution and it is what we all SHOULD be using.

William Smith

8/10/2022 04:24:12 pm

Hi Jon. It's a Campagnolo Nuovo Valentino which I've owned from new in the early 1980s. Had to get a new, flat hanger for my Dawes project as the original offset hanger interfered with the rear dropout. Old hanger had the Campag thread, which was slightly different from the thread in the new hanger, Discovered that the latter is the same thread as a rear wheel spindle, so I cut off a portion of one of those to mount the derailleur on. Would have preferred a bolt, but difficult to source one with the correct thread, although I'll keep my eyes open for one.

Shellie Leonard

8/21/2023 11:45:30 am

I'm working on an old 1973 Nishiki Custom Sport. Upgrading the rear derailleur to a Shimano 105. I ordered a hanger off ebay, but was mistaken. Can you possibly help me with what I need to make this happen? I have a photo of the rear drive side of frame if you would like to see that.

Jon Vara

8/24/2023 05:50:54 am

Hi Shelley

Send me an email at jon@redclovercomponents.com and we can sort this out. It would be useful if you could send a photo of the hanger in question--the one you bought that doesn't fit.

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I'm a chainring czar and editor in Cabot, Vermont. You know, where the cheese comes from.

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Derailleur Hangers Demystified (2024)