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3-arm "circular" cranks vs. 5-arm starfish design

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3-arm "circular" cranks vs. 5-arm starfish design

Old 02-02-21, 11:16 PM
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parkerposey
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3-arm "circular" cranks vs. 5-arm starfish design

Hi all. Currently building up a pretty frame from the 80s, and I like the look of the Dia-Compe ENE Ciclo double crankset -- I can't upload a photo, but the design has 3 arms, and the arms branch as they approach the outer ring, creating three 'circles', in contrast to the 'starfish' shape of standard 80s cranks. Other details include cold-forged arms. I read that this process makes them even stronger, but this made me wonder if the rings, on the other hand, were not more flexible than rings with 5 arms of support, if the "circular" design improves stiffness relative to 'radial' arms, etc., etc..

My question is for anyone who's experienced both this 3-arm design and the more common 5-arm starfish of 80s/90s Sugino cranks etc. What were your impressions, how did they compare? Thanks in advance for your input.
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Old 02-03-21, 03:32 AM
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I have one bike that has a three arm Campy crank and the rest of my bikes all have five arm Campy or Ambrosio. At my age and strength , honestly, I can’t tell the difference in rigidity . I would go with the cranks that give you the best ratios gear wise to fit your type of riding.
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Old 02-03-21, 03:48 AM
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Absent finite element analysis or accurate mechanical testing, you have no way of knowing which set of arms is stiffer.

Neither does anyone else.

The various patterns you see in cranksets are all (supposedly) the result of careful compromise between the various factors of material cost, manufacturing cost, form, and function.

And I suggest that that is the order in which most manufacturers today consider them.
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Old 02-03-21, 05:37 AM
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Here’s a photo of that Dia Compe crankset from the manufacturer’s site:


FWIW, there are a few other 3-arm sets currently available: Herse/Compass, Sun XCD, Andel.
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Old 02-03-21, 06:02 AM
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Just to be a pedant, the term Starfish is used to refer to one particular crankset made by Mavic. The rest are generally called 3 pin, or 5 pin.
Mavic courtesy Velobase.

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Old 02-03-21, 06:34 AM
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I have a TA three-arm crank on a Gitane. Can't tell any difference from the TA Cylotouriste on a <otobecane.

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Old 02-03-21, 06:34 AM
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I agree there's no straightforward way to prove greater stiffness, at least at the consumer's level of technology. I'm also not clear on whether stiffness matters to a rider or is perceptible. But assuming cold-forged cranksets are stronger, you can get the same strength, if not stiffness, with the same or lesser amount of material. The sales metric, as with frames, is less mass with equal durability. So if the weight of this chainset is more like that of a Rene Herse than another double capable of 46/30 which is not cold-forged (I can't think of one at the moment), there's a tangible difference. Real nice looking design, though!
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Old 02-03-21, 06:49 AM
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My suspicion is that the 5 pin is designed to survive lateral forces from accidents. A three pin would be optimal for driving a chain.
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Old 02-03-21, 06:56 AM
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I don't know how much riding the OP is going to do, but my choice would come down to the availability of different chainrings.

Last edited by seypat; 02-03-21 at 04:58 PM.
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Old 02-03-21, 07:13 AM
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Originally Posted by seypat View Post
i don't know how much the op is going to do, but my choice would come down to the availability of different chainrings.
+ 1.
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Old 02-03-21, 08:01 AM
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Originally Posted by seypat View Post
I don't know how much the OP is going to do, but my choice would come down to the availability of different chainrings.
This is the best answer, assuming OP plans to ride the bike far enough to wear out a chainring. I would modify to say "availability and cost of replacement chainrings" though. If there's a $50 crankset, but the chainrings cost $75 versus a $75 crankset with rings that cost $50 or the BCD is common enough to enable me to use a wide variety of rings, I'm going with the latter every time.

That said, I do like the look of that crankset.
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Old 02-03-21, 08:02 AM
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Dia Compe has a 96 BCD. Old Shimano 600 cranks are 95 BCD. They could have at least revived an old standard and made some 30t chainrings.
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Old 02-03-21, 08:41 AM
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It should be said too, that if you already have a Sugino crankset they are great and sturdy and polish beautifully.
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Old 02-03-21, 09:02 AM
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Originally Posted by francophile View Post
This is the best answer, assuming OP plans to ride the bike far enough to wear out a chainring. I would modify to say "availability and cost of replacement chainrings" though. If there's a $50 crankset, but the chainrings cost $75 versus a $75 crankset with rings that cost $50 or the BCD is common enough to enable me to use a wide variety of rings, I'm going with the latter every time.

That said, I do like the look of that crankset.
Or they only come in tooth sizes that you don't want. I went through this recently trying to assemble a triple for a modernish build. I don't care for a compact double or rear clusters with pizza sized sprockets. That's just me. I ended up going back in time to the tried and true 110/74 BCD. In fact, the build is turning into a middle finger at the components companies for their never ending planned obsolescence.

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Old 02-03-21, 09:06 AM
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Originally Posted by bark_eater View Post
They could have at least revived an old standard and made some 30t chainrings.
Like the 86BCD that was popular for touring back in the day. You could run it as a compact double or a triple. Very versatile like the 110/74 BCD. But nooooo, they have to make something new that crosses over to nothing.

Now, get off my lawn!

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Old 02-03-21, 10:31 AM
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Like someone else mentioned, the most important factor here is the gearing.

there should be a sufficiently fast jump between the two ratios, no dead space in between, and a versatile granny gear useful for both climbing and flat terrain. You shouldn't feel like you have to always compensate by changing thenresr cassette ratio when changing between front chainrings.
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Old 02-03-21, 10:40 AM
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It's 90% marketing, With good design, you can optimize anything from 3 to 6 stars for any standard of stiffness and strength you want. There will be minor weight and aero trade-offs but not race winning or losing. The final and ultimate solution will not happen until software people can encrypt "bling" into the FEA code.
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Old 02-03-21, 11:07 AM
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Wow, this forum is the best thing since sliced bread! Thank you everyone for your input! I have to say that I agree with the latter posts, in that the gearing is the main deciding factor -- this is the reason for building this bike to begin with: 10%+ hills in my neck of the woods. Initially I chose this crankset because I couldn't find any cheaper options for 48/36, but have since found a few (Sugino is top contender for competition with this Dia-Compe Ene Ciclo, for me at the moment). Glad to hear that there aren't any horror stories of these differently-designed rings, or with 3-pin designs in general. That was my main fear and reason for posting.

So, beyond the gearing choices, it sounds like it's mostly an aesthetic difference. (Still grateful for any input anyone may want to share!)
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Old 02-03-21, 11:14 AM
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I think the difference in stiffness would be marginal unless you are a 240lb bodybuilder cranking out 500+w up a hill in a regular basis.
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Old 02-03-21, 11:50 AM
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The Andel crank I mentioned above comes in 46/30t configuration if you want some serious climbing gears. I put one on my Rivendell Roadini.
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Old 02-03-21, 08:30 PM
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Originally Posted by seypat View Post
I don't know how much riding the OP is going to do, but my choice would come down to the availability of different chainrings.
Yep. 110 and 130mm 5-pin rings will be around after the cockroaches are gone. Availability of 3-pin rings is sketchy at best, even when the cranks are in production.
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