Ofmega crank question
#1
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Ofmega crank question
Posting here rather than mechanics sub forum as it seems like a vintage manufacturing question. I’m working on an 1980s bike with an Ofmega crank that I got used nearly 3 years ago. I know no history of it, but it seems low miles but stored poorly for maybe 30 years and probably seldom if ever serviced. Pulling the crank showed marks in the taper in the crank. I just thought perhaps at one time someone used an improper crank puller, although the rest of the crank wasn’t scratched up.
![](https://cimg3.ibsrv.net/gimg/bikeforums.net-vbulletin/2000x1504/img_2540_3a4c3526f478ecb9d1b47d1af1fb2cb0f43d2cdf.jpeg)
![](https://cimg4.ibsrv.net/gimg/bikeforums.net-vbulletin/2000x1504/img_2542_a61189b3b71de8bffe5361a2083ed407dfc7676b.jpeg)
Kinda hard to photograph, but this is how it is along with the nds crank also. Things tighten up fine and no riding problems. Searching the internet however for similar Ofmega cranks shows the same thing. People selling these cranks don’t picture it, but on most one can get a sense of it from pics. Here are photos from the net:
![](https://cimg2.ibsrv.net/gimg/bikeforums.net-vbulletin/800x600/img_0506_52a704473ae66d6a8f6a41a0549efe793c80496c.jpeg)
![](https://cimg4.ibsrv.net/gimg/bikeforums.net-vbulletin/800x600/img_0505_77237406cee6ef6b8c049af3e992e24fabf7c4cc.jpeg)
So, what is this? Was it something to do with the manufacturing process? My Park tool puller didn’t cause this, and it seems that most have this.
![](https://cimg3.ibsrv.net/gimg/bikeforums.net-vbulletin/2000x1504/img_2540_3a4c3526f478ecb9d1b47d1af1fb2cb0f43d2cdf.jpeg)
![](https://cimg4.ibsrv.net/gimg/bikeforums.net-vbulletin/2000x1504/img_2542_a61189b3b71de8bffe5361a2083ed407dfc7676b.jpeg)
Kinda hard to photograph, but this is how it is along with the nds crank also. Things tighten up fine and no riding problems. Searching the internet however for similar Ofmega cranks shows the same thing. People selling these cranks don’t picture it, but on most one can get a sense of it from pics. Here are photos from the net:
![](https://cimg2.ibsrv.net/gimg/bikeforums.net-vbulletin/800x600/img_0506_52a704473ae66d6a8f6a41a0549efe793c80496c.jpeg)
![](https://cimg4.ibsrv.net/gimg/bikeforums.net-vbulletin/800x600/img_0505_77237406cee6ef6b8c049af3e992e24fabf7c4cc.jpeg)
So, what is this? Was it something to do with the manufacturing process? My Park tool puller didn’t cause this, and it seems that most have this.
#2
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I don't see any such marks on the Ofmega and Avocet (made by Ofmega) cranks I have here. The blemishes look consistent with galling damage. Has the bike been left outdoors and/or in a corrosive environment (e.g. road salt, ocean breeze)?
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#3
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No history on bike, but no salty environment around here. I just found it curious that these gouges were all at 45 degrees to the taper flats and were present in so many others that I saw pics of. They appear to be mechanically caused and there wasn’t any sign of any other metal or debris upon disassembly either. These marks are also at the very outside ends of the taper where galling shouldn’t happen as the crank spindle didn’t reach that far.
#4
I think someone used an extractor with a mushroomed part.
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#5
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The hole was made - possibly tapered - but round; then the taper was machined. What you see is the part of the hole not removed as the taper was made - that's why you see it of the outer part of the taper flat and the bolt seat (the taper is smaller there).
It's not a problem, the crank doesn't bear on the axle at that place but on the corners.
It's not a problem, the crank doesn't bear on the axle at that place but on the corners.
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#6
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The hole was made - possibly tapered - but round; then the taper was machined. What you see is the part of the hole not removed as the taper was made - that's why you see it of the outer part of the taper flat and the bolt seat (the taper is smaller there).
It's not a problem, the crank doesn't bear on the axle at that place but on the corners.
It's not a problem, the crank doesn't bear on the axle at that place but on the corners.
As a side note, these cranks seem quite light with a sort of delicate look and feel. 144bcd doesn’t do it for me though.
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#7
Just make sure you never combine the cranks to a different brand BB as Ofmega uses a proprietary BB with tapers that only works best with Ofmega cranksets.....
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#8
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Interesting on the bb tapers. This 1984? Torpado has a Campagnolo bb and I am about 99% sure it is stock. I’m not planning on switching anything out on it. It would be another bit of Italian confusion such as I read about other campy bottom brackets and cups.
#9
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I have experienced a case where LBS was unable to remove an Ofmega crank arm - their extractor tips (multiple tools)
were too large in diameter, hanging up on the top of the crank arm rather than sliding through to engage the crank spindle end.
They almost stripped out the extractor threads by exerting too much force.
My solution was to cut a piece of drill rod stock so that it extended beyond the end of the crank spindle. I inserted
the drill stock and then set the crank extractor tool so that it made contact on the drill stock, which was centered
in the spindle. The crank came off cleanly.
There is a residue of marking on the crank arm similar to yours.
were too large in diameter, hanging up on the top of the crank arm rather than sliding through to engage the crank spindle end.
They almost stripped out the extractor threads by exerting too much force.
My solution was to cut a piece of drill rod stock so that it extended beyond the end of the crank spindle. I inserted
the drill stock and then set the crank extractor tool so that it made contact on the drill stock, which was centered
in the spindle. The crank came off cleanly.
There is a residue of marking on the crank arm similar to yours.
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#11
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I thought of that, but the marks go nearly to the bottom of the tapers. The cranks would have surely popped free long before the extractor would have been threaded that deep. The many others seen on internet searches would have all have suffered the same fate.
#12
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![](https://cimg2.ibsrv.net/gimg/bikeforums.net-vbulletin/2000x1504/img_20240219_160548720_aaeaf46476aff00c2d29dfd0a259386192a2135b.jpg)
#14
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I have experienced a case where LBS was unable to remove an Ofmega crank arm - their extractor tips (multiple tools)
were too large in diameter, hanging up on the top of the crank arm rather than sliding through to engage the crank spindle end.
They almost stripped out the extractor threads by exerting too much force.
My solution was to cut a piece of drill rod stock so that it extended beyond the end of the crank spindle. I inserted
the drill stock and then set the crank extractor tool so that it made contact on the drill stock, which was centered
in the spindle.
were too large in diameter, hanging up on the top of the crank arm rather than sliding through to engage the crank spindle end.
They almost stripped out the extractor threads by exerting too much force.
My solution was to cut a piece of drill rod stock so that it extended beyond the end of the crank spindle. I inserted
the drill stock and then set the crank extractor tool so that it made contact on the drill stock, which was centered
in the spindle.
Every crank extraction that screw gets placed in the end of the axle, and the extractor bears on it.
#15
Senior Member
A close-up of a new old stock arm might help solve the mystery.
#16
Stop reading my posts!
applies to SOME but not to EVERY Ofmega spindle, likewise do not assume it applies to each and every Avocet (rebranded Ofmega) spindle, either. Best to consult Sutherlands for the fine points.
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I wasn't aware of Ofmega proprietary spindle tapers. I replaced the original 144mm Ofmega cranks on the Bianchi with newer 130mm Bianchi-branded cranks that may well have been made by Ofmega, as well.
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#18
Stop reading my posts!
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#19
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Only true for early production Ofmega. By the late 70s, Ofmega adopted the same taper as Campagnolo. If your crank uses the early taper, it will sit too far out on a Campagnolo-type taper spindle.
#20
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Some pics for you folks fluid in Italian and Campagnolo. The only other Italian one I have is a Shimano that I used for a short time on a Frejus I no longer have. That one in 109mm allowed me to use a first generation Superbe crank on that 64 Frejus instead of the cottered 47-50. The Torpado I am cleaning up is stamped 84 on the BB. Shell is 70mm and the spindle is 115.5 withe the drive side being about 2.5mm longer than the nds.
![](https://cimg7.ibsrv.net/gimg/bikeforums.net-vbulletin/2000x1504/img_2555_6ba75e485a79976339df853c19e0ccf5ec191530.jpeg)
Loosely mounted for photo
![](https://cimg9.ibsrv.net/gimg/bikeforums.net-vbulletin/2000x1504/img_2552_a6d0bac18a15fd54d076d124b91d0970c9f2d234.jpeg)
Thick cup vs thin?
![](https://cimg0.ibsrv.net/gimg/bikeforums.net-vbulletin/2000x1504/img_2553_efeb7f0f392fc33aeff22acc56c0492d1a81139e.jpeg)
NDS
![](https://cimg2.ibsrv.net/gimg/bikeforums.net-vbulletin/2000x1504/img_2549_ffd3d3ba775154ae753dbdf2c355a55efffb0717.jpeg)
Quite a difference in center section, both marked 70
![](https://cimg3.ibsrv.net/gimg/bikeforums.net-vbulletin/2000x1504/img_2550_21d36dbe7a19682b10e875e6251acbec5ea37b69.jpeg)
Tapers appear the same
The spindle side by side photo is distorted as the front Shimano spindle is 109mm and the back Camp that is on this bike is longer at 115.5.
![](https://cimg7.ibsrv.net/gimg/bikeforums.net-vbulletin/2000x1504/img_2555_6ba75e485a79976339df853c19e0ccf5ec191530.jpeg)
Loosely mounted for photo
![](https://cimg9.ibsrv.net/gimg/bikeforums.net-vbulletin/2000x1504/img_2552_a6d0bac18a15fd54d076d124b91d0970c9f2d234.jpeg)
Thick cup vs thin?
![](https://cimg0.ibsrv.net/gimg/bikeforums.net-vbulletin/2000x1504/img_2553_efeb7f0f392fc33aeff22acc56c0492d1a81139e.jpeg)
NDS
![](https://cimg2.ibsrv.net/gimg/bikeforums.net-vbulletin/2000x1504/img_2549_ffd3d3ba775154ae753dbdf2c355a55efffb0717.jpeg)
Quite a difference in center section, both marked 70
![](https://cimg3.ibsrv.net/gimg/bikeforums.net-vbulletin/2000x1504/img_2550_21d36dbe7a19682b10e875e6251acbec5ea37b69.jpeg)
Tapers appear the same
The spindle side by side photo is distorted as the front Shimano spindle is 109mm and the back Camp that is on this bike is longer at 115.5.
#21
IIRC, The Ofmega Mistral cransets I had used on a few builds, might have still required Ofmega BBs to get the chain lines to run correctly, and those cranksets were already from the 80's.....
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I'll never understand the Italians copying the looks and designs of one another. Did they not have a proper patent system?
Whenever I see Ofmega cranks, I immediately see Campagnolo, maybe with the arms "mexicaned" out like E. Merckx' bike.
Whenever I see Ofmega cranks, I immediately see Campagnolo, maybe with the arms "mexicaned" out like E. Merckx' bike.
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![](https://cimg3.ibsrv.net/gimg/bikeforums.net-vbulletin/914x697/ofmega_spindle_fit_80b6af46bdde7f1e8dcca99d7af3f0bfba4572cb.jpg)
![](https://cimg1.ibsrv.net/gimg/bikeforums.net-vbulletin/1008x535/crank_arm_seat_43ff5143a4357c5a91377c4f564f38a532a8cd0b.jpg)
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#24
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I notice that one has the marks that I have mentioned and pictured.
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I am not an engineer, but I wonder if that little bit of space in the middle of the flat would make it less likely to seize?
As oneclick said, the middle of the flat shouldn't be bearing any load.
As oneclick said, the middle of the flat shouldn't be bearing any load.