History of Aluminum Cranks

During the development of our new René Herse cranks over the last two years, I have been thinking a lot about crank design. Modern cranks are an interesting story of standards that evolved until nobody remembers why they were adopted in the first place. Here are a few questions that I tried to answer:

  • Why do triple cranks have two different bolt-circle diameters?
  • Why do makers offer “compact” and regular cranks, when you could make 53-tooth chainrings for “compact” cranks and offer only a single, more versatile model?
  • Why do “road” cranks have five-arm spiders, but many “mountain bike” cranks have only four, and some only three?

When something doesn’t appear to make sense, it often helps to look at how it evolved over time.

The first successful aluminum cranks were introduced in 1933 by Stronglight (photo at the top). They used a square taper fitting on the spindle instead of the cotters used by most steel cranks at the time. As their name implied, these cranks were strong and light.

They had one drawback. The chainring attached to a small flange on the right crankarm, as was common among cranks at the time. If you ran two or more chainrings, the additional chainrings attached to the big ring with bolts, nuts and spacers. Installing the chainrings on these cranks is a fiddly business. The small bolts are under-dimensioned. It is hard to tighten them enough without breaking them.

The next modern aluminum crank was offered by René Herse in 1938 (above; 1950s tandem version shown). Herse mounted his chainrings to a larger spider instead of a flange. Using three arms and a bolt-circle diameter of 70 mm, these cranks preserved all the advantages of the Stronglight, while making it much easier to attach the chainrings. The cranks could be set up as a single, double or triple with any chainring combination down to 24 teeth.

When Herse began to offer complete bicycles in 1940, his cranks were available only on his bikes.  If you wanted a René Herse crank, you had to buy a René Herse bike. This precluded a more widespread adoption of this great design.

Starting in the late 1940s, Tullio Campagnolo adopted a number of cyclotouring components for racing. The first was the Gran Sport derailleur, which was based on the Nivex parallelogram derailleur. (Campagnolo famously bought two Nivex derailleurs from Alex Singer the year before he introduced the Gran Sport. You can read Bicycle Quarterly’s article on the development of the Gran Sport here.) The Gran Sport was so successful that it set the mold for all modern derailleurs. Even Shimano’s electronic Di2 rear derailleur can trace its ancestry directly to the Gran Sport.

When Campagnolo offered his first cranks in 1958 (above, 1965 version shown), Campagnolo used five arms for the spider instead of Herse’s three arms. Perhaps he thought that racers needed more support for the chainrings? Like Herse, he considered the smallest chainring his customers would use.  At the time, most racers used a small chainring with 47 teeth. The result was a 151 mm bolt-circle diameter.

Around the same time, triple cranks were becoming popular among racers. Campagnolo offered a “Strada” model that simply used longer chainring bolts and nuts, plus spacers, so you could bolt a third chainring to your cranks. Of course, a triple with a small ring of 47 teeth was of little use to most riders.

Some mechanics instead retrofitted Campagnolo cranks with a third ring, with a smaller bolt circle (from Stronglight or TA). They drilled holes into the crank’s spider, tapped them, and attached the third ring with spacers. The photo above shows one of these home-made conversions. Since it’s a tandem, you see a fourth chainring, which is on the other side of the bike.

In the 1970s, Campagnolo began offering a factory-made version of this design. The Campagnolo triple appears to have been the first production crank with two different bolt-circle diameters.

For decades, most component makers copied Campagnolo, sometimes with small modifications. Shimano’s cranks used a 130 mm bolt-circle diameter that allowed using chainrings down to 38 teeth. Campagnolo reduced their bolt-circle diameter first to 144 mm (42-tooth chainrings), then to 135 mm (39-tooth chainrings).

When mountain bikes popularized triple chainrings, the crank makers copied the dual bolt-circle diameter of the old Campagnolo “retrofit” triple cranks (above; the second set of bolts is hidden on the other side of the crank). Component makers reduced the bolt-circle diameters to allow the use of smaller chainrings, but did not reexamine whether it made sense to have two different bolt circles on the same cranks.

During the 1980s, Campagnolo tried to break away from the dual-bolt circle diameter “retrofit” cranks. Their Gran Sport Touring, Victory and Triomphe cranks had a smaller 116 mm bolt-circle diameter (above), so they could be equipped as doubles or triples, with chainrings down to 36 teeth. (It appears that Campagnolo could not envision anybody using rings smaller than 36 teeth.)

The basic idea was sound, but it fell by the wayside as Shimano began to dominate the component market. When Campagnolo offered a road triple again in the 1990s, they were back to two different bolt circles.

In recent years, Shimano’s mountain bike cranks have moved away from the five-arm spider. To save weight, they now use four arms. However, the two bolt circles remain.

On triple cranks for the road, Shimano remains faithful to the tradition of five-arm spiders and multiple bolt circles, even though the extra arms and larger bolt circle for the outer rings provide no advantage.

In recent years, many riders found they needed chainrings smaller than the 39- or 38-teeth offered by racing cranks. Crank makers could have reduced the bolt-circle diameter further, just like Campagnolo had in the past. Instead, they offered additional “compact” models (above) with a 110 mm bolt circle. This bolt circle limits the smallest ring to 34 teeth, even though many riders could use smaller chainrings. The crank makers continue to offer the larger bolt circles for their “standard” cranks.

Even today, the old René Herse design remains the most logical: It allows using any chainring combination. It’s lighter than most modern cranks, because it uses only as much material as needed. The Herse cranks did not serve as a template for the industry because they were too rare and mostly unknown when “modern” cranks were introduced during the 1980s, 1990s and 2000s. Instead, everybody copied the Campagnolo cranks, which initially were intended for ultra-strong racers, and then retrofitted with a third chainring for those not strong enough to climb hills in a 47-tooth (and later 42-tooth) chainring. It appears that nobody took a clean sheet of paper and tried to come up with a more rational design for a bicycle crank.

We are proud to reintroduce René Herse cranks, so that today’s cyclists can enjoy the benefits of light weight, narrow tread (Q factor), unlimited chainring choices, and easy setup.

About Jan Heine, Editor, Bicycle Quarterly

I love cycling and bicycles, especially those that take us off the beaten path. I edit Bicycle Quarterly magazine, and occasionally write for other publications. One of our companies, Bicycle Quarterly Press publishes cycling books, while Compass Bicycles Ltd. makes and distributes high-quality bicycle components for real-world riders.
This entry was posted in Product News, Rene Herse cranks, Testing and Tech. Bookmark the permalink.

42 Responses to History of Aluminum Cranks

  1. Alex Wetmore says:

    What about Stronglight cranks with a single 86mm BCD for all three rings, and the Japanese clones of these from SR and Sugino? This standard was briefly popular in the early 80s on touring bikes, but then everything moved to 110/74. I don’t know when the 86mm standard was initially released and why it didn’t become more popular.

    It only allows a inner ring down to 28t, perhaps 110/74 gained popularity because it could go down to 24t?

  2. Jason Hansen says:

    Has there been a release date set for the Rene Herse crank?

    • No exact date. We are still working on the last details. They should be ready this fall.

      • Greg says:

        Jan, this is some good info. on crankset history. Thanks for posting it. Looking forward to the intro. of the Herse cranks. A few minor comments from an admitted Campagnolo nerd:
        1) The old 151 bolt circle will accept a 43-tooth ring (but Campagnolo never offered one). CT of Japan (now retired, sadly for us…) used to make them, as did Highpath Engineering, I’m guessing (sadly, they no longer make custom chainrings either!).
        2) The 144 pattern will accept a 41-tooth ring. Campagnolo (and others) did make 41-tooth rings for the 144 pattern, though the Campagnolo ones are difficult to find now.
        3) The smallest ring made for the 116 pattern was 35. Campagnolo (among one or perhaps two others) made them in that size. I like those 116 cranks, but there are no other rings out there for those than the NOS Campagnolo ones, pretty much. Almost no one else used that bolt pattern (I think Gipiemme may have been the only other manufacturer to do so).
        Also, those 116 cranks were only available in 170 mm lengths, with one exception. In 1988 there was a Victory “ATB” crankset that was 74/116 that was made in 175 mm. I like to leave off the inner ring, and run those as a 35/50 double.
        4) The old Stronglight 100 series cranks are very flexible in chainring combinations. That BCD of 86 will take as small as a 28-tooth, and those cranksets were available in various lengths (at least 165, 170, and 175, anyways). Plus, the 86 mm BCD rings seem to be reasonably available as NOS parts.
        Cheers,
        Greg

      • Thank you for adding the info. The 144 mm BCD rings with 41 teeth tend to have the chain touch the chainring bolts, from what I hear…

      • Greg says:

        Jan, regarding your 144/41 comment, they don’t touch the chainring bolts, but sometimes they can touch the tip of the spider arms, depending on the chain used, I think…. Campagnolo actually machined off a bit of the inner side of each spider arm tip when they sold the cranksets (new) with a 41-tooth inner ring.

      • You are right! The chainring bolts are countersunk anyhow. I am still traveling, so I can’t check my references…

        Somebody else posted this after the comments closed:

        Relative to your wonderful article on the history of aluminum cranks, you failed to mention the contemporary White Industries VBC (variable bolt circle) offerings. Seems like an elegant and intelligent solution to me.

      • Olivier says:

        For the record, Miche makes 116 bcd rings for their junior crank (Miche Young). Hard to get, though.

      • Greg says:

        Olivier, thank you for that info. I am pursuing obtaining some of those Miche chainrings from Miche (through a USA distributor).

    • Greg says:

      Olivier:
      What size are the chainring bolt holes, and what is the I.D. of the ring (inner edge) itself? Where can one obtain some of the Miche rings? The old Gipiemme ones that I am aware of are also for junior cranks, use mini-bolts (8 mm instead of 10 mm), and the inner edge diameter is a bit larger than the Campagnolo rings, perhaps by 2-3 mm. So one of those can be drilled out and will physically fit on the spider, but the chainring nut has to protrude inboard from the inner ring, and things don’t look quite right once assembled….

      • Olivier says:

        The rings fit a Triomphe crank. I had to use shorter chairing bolts as the rings are slightly thinner. The crank’s spider was not as wide as the rings so I filed them a bit. Normal bolts, not sure what you mean by inner edge. I got mine on eBay, and some UK/AUS retailers carry them. I later found that a local distributor (Marinoni) has them.

  3. Chris Lowe says:

    Are close enough that you give a ballpark price? Hoping it will be less than the last run of TA Cyclotourist cranks.

  4. Fred Blasdel says:

    It’s odd that Stronglight’s 86 BCD cranks aren’t in your timeline, given that they (and their clones by SR) were sold as standard equipment in very large quantities during the bike boom and provided all the single-spider advantages you promote in the Herse cranks. Also that both T.A. and Campagnolo had a long history of making ~116bcd 3-arm cranks that came stock with ‘standard’ rings.

    These things didn’t go out of style for no reason at all despite being easier to manufacture. It does you a great disservice to pretend that “the extra arms and larger bolt circle for the outer rings provide no advantage”

    The problem is that chainrings are quite flexible laterally, and making them extend far above their attachment point turns them into a diving board for the chain — when upshifting to a 52t outer on a 50.4 crank, the ring will flex out of the way of the chain quite noticeably for several mm. I’ve bent a number of 86bcd rings just from shifting, and it is infuriating when this happens enough that the chain can force itself down between your middle and outer. A friend *folded* his 44t 94 BCD outer just stepping on the pedals from a stoplight.

    There’s a reason that racers in the 50.4bcd era used forged ‘adapteur’ spiders for 6-bolt 152 BCD ‘criterium’ rings.

    The interesting thing to me about you and Hahn’s new crank is how you’re making the chainrings — could you publish more details about them sometime?

    • I have used TA rings on many bikes and tandems – only up to 48 teeth usually, but the diameter is close to the same – without any problems. When you look at shifting a “long-chain” tandem, you realize that the stresses are pretty high. So I am surprised that you fold chainrings.

      THe “adaptateur” spiders were used not to stiffen the crank, but to facilitate chainring swaps. Many racers used different ring sizes for each stage, and the poor mechanics had to switch them every night.

      The Herse rings will be a full millimeter thicker than current TA rings, so they should be significantly stiffer.

      The crank is made for Compass Cycles and Rene Herse Bicycles, my friend Hahn Rossman (of Rossman Cycles) is not involved. The rings are CNC machined at a factory that specializes in high-end chainrings.

  5. Wayne Sulak says:

    What about chain ring availability?

  6. Christian McMillen says:

    Hi
    What FD is that with the Campy Record crank please? Thanks.
    Christian

  7. Harpo says:

    Any news on Herse crankarms longer than 171mm?

  8. Chuck Davis says:

    Well done and readable
    I had a 144bcd 41T on my old Raleigh 531 w/ Superbe cranks from Avocet

  9. superfreak says:

    i dont trust that small of a bolt circle. heres a pic from the internets
    http://farm6.static.flickr.com/5047/5641452266_2a45200a72.jpg
    i also had a freind who bent over a big ring like the picture. small bcd mebbe ok for small racers but what about big heavy powerful riders

    • That photo looks like the rider hit something. Even if you “cross-chain,” the chain pulls mostly in line with the chainring. Think about the forces of a strong tandem like this one. The torque a team like that puts on the chainring is more than any single racer ever could muster.

      • John says:

        I’ve folded chainrings in half before. It’s not from cross-chaining. Short uphill sprint, lost a chainring bolt….3 arms is a really bad idea.

      • How many “chainrings” have you folded? Which models? I haven’t seen or heard of this before… I doubt you are stronger than the strongest tandem teams, so I wonder what else may have gone wrong. Misaligned BB shell perhaps? It’s hard to know.

        All I know is that thousands of René Herse cranks were made, many were ridden very, very hard, yet in all my research, I haven’t heard of chainrings folding.

  10. mander says:

    Doesn’t a bigger BCD result in greater stiffness and less likelihood of folding a chainring?

    What happens if a Rene Herse crankset loses a bolt?

    • How often do you fold chainrings? I don’t know of a single instance, unless you bend them when you hit a rock or log. In that case, any ring will bend.

      If you loose a bolt on a RH crankset, nothing happens. The rings are set tight against the spider… What if you loose two? We’ll try that at some point. If you loose three, I am sure you won’t be able to ride any longer.

      • mander says:

        “If you loose a bolt on a RH crankset, nothing happens. The rings are set tight against the spider”

        Have you tested this empirically?

      • No, but I have seen bikes with a bolt missing. Lyli Herse used aluminum chainring bolts on her bike. Granted, that was during the 1980s, after she had stopped racing… We’ll see what happens once FSA’s 3-arm mountain bike cranks have been out there for a while. Will mountain bikers fold their chainrings? It seems that FSA has full confidence in the 3-arm design…

  11. rory says:

    the 2 bcd for mtn bike cranks might not be going away, but there seems to be something in the works for double mtn bike cranks, with a larger cassette in the rear. also, fsa has gone down to a 3 arm crank double:
    http://www.fullspeedahead.com/products/115/AFTERBURNER-COMPACT-386-MEGAEXO
    I think it’s funny that industry has somewhat caught up with rene herse.

  12. TimJ says:

    Great post, thanks as always. I have three different BCDs on my many bikes (2 Shimano, 1 Campagnolo) and am continually disappointed at the selection of chainrings for any of them. The four different axle mounting systems is less of a frustration, but they sure account for a lot of different tools. I sure wish standardization on the Herse model would have happened long ago!

  13. Jim says:

    Jan, I don’t believe that it was the case that Campagnolo started marketed the 1048/5 triple crankset (with the fixed 36 teeth inner chainring) until sometime in the early 1970’s. None of the Velo-Base catalog scans show this model of the Campagnolo in their scans for the 1960’s period.

    This crankset appears on the Schwinn “Diamond Jubilee Paramount” P-15 model that was first produced by Schwinn in 1970 (Schwinn celebrated their “1895 Diamond Jubilee 1970″ that year).

    I had a Schwinn dealer catalog that I obtained some time ago for the 1975 Schwinn bikes (unfortunately I no longer have this catalog). It referred on one page to the Campagnolo triple as the “Diamond Jubilee” crankset. I’ve often wondered if Schwinn was not responsible for Campagnolo making the first production 1048/5 crankset, initially for their P-15 Paramount touring model.

    • According to Chuck Schmidt’s usually very reliable Campagnolo timeline, the Campagnolo triple was introduced in 1961. I recall seeing an early or mid-1960s Rebour drawing of a TdF bike that had snuck in with those cranks, even though triples were not allowed in the Tour (according to Rebour).

      • Greg says:

        The ‘normal’ triple on the 144 BCD arms (I suppose on the 151 BCD arms as well, as the special chainring bolts/spacers will fit, but I’ve never seen one) was available very early on. It only required longer chainring bolts and a proper spacer. The ‘special’ triple with its fixed “your choice of 36-teeth” inner chainring came later (1970 sounds about right, but I am not sure exactly when it was introduced).
        The 1960 catalog (#14) does not show any triple components.
        The 1967 catalog (#15) shows a 151 triple (44 min.) but no BB parts to support it.
        The 1968 catalog (#16) shows the same stuff as in the 1967 catalog.
        The 1974 catalog (#17) shows the ‘special’ triple (1048/5, 170 length only) for the first time, as well as BBs to support it.

      • OK, thank you for correcting this. I updated the post to correct the error. Does that still make Campagnolo the first “dual bolt-circle” cranks? I can’t think of any others…

    • Greg says:

      No, I would say that the Stronglight 49D was the first…. (50.4/122/86). Plus, it was a ‘triple threat.’ :-)

      • I guess if you count all those as independent bolt circles. In fact, I think it was ROSA who first offered triples for the Stronglight in the 1930s. Stronglight only offered very limited chainring sizes, which left an opening for other companies to offer the chainrings people really wanted. That is how TA got started (after their crazy front-wheel drive bicycle went nowhere).

  14. mander says:

    I have never folded a chainring myself but it does happen. It has happened twice to a guy I know out here in Vancouver, and reportedly rather than being e.g. from going over a log they were “jra” type failures in both cases. http://www.fearlessgearless.com/2008/03/opps-i-did-it-again

    • I looked at those photos… Impressive, but the rider did not fold the chainrings, but broke the entire cranks, just spinning along. Neither of the cranks he broke were forged: One was machined from billet, the other cast. Perhaps using forged cranks would have prevented these failures?

      • Greg says:

        I would second that. He broke two crankarm spiders, he didn’t ‘fold’ any chainrings. Maybe his chain was way too loose, and jumped partially off, then jammed? Difficult to say. In my experience, a very small percentage of riders breaks lots and lots of parts repeatedly (crankarms, BB spindles, dropouts, frames, handlebars, etc.), whereas almost everyone else never breaks anything of significance. … and it’s not size/strength related. Some folks’ pedaling style must be really lumpy (or whatever) and impart crazy stresses into the components, drastically shortening their fatigue life.

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