itf6 

In the process of learning how to build up bikes and I sometimes forget to do appropriate research here on BikeForums!

Case in point, I recently purchased an older Ofmega crankset from kijiji to replace a damaged crank on my wife's bike and didn't realize there were issues using a standard square taper BB spindles. I've done some digging and found some helpful information on BF but hopefully I can get some further info with a post as well. Here are my issues:

Identification - as far as I can tell it's an 80s Ofmega crank but for whatever reason I can't place the model researching online (BF, Velobase, ebay ads, etc.). Any help IDing the model is much appreciated! Pics attached. I'm thinking 80s because it is very close to the Competizione, Strada, models but the black "trim" is throwing me off.

BB Shell - Kijiji (again) has an Ofmega BB for sale at the moment (seller says 116.5mm length), although it's listed quite high, but that's fine if that's what it takes, the only concern is that my understanding is that Ofmega, being Italian, means made for 70mm BB shell, while the bike has a 68mm BB shell. Am I able to use the BB spindle and play around with different depth NDS cups (with the right threading of course)?

Non-Ofmega Spindle - I've also read that using an ISO spindle might do the trick but also that a symmetrical JIS spindle will also work. Maybe I'm just looking to put my mind at ease (it's the wife's bike after all!) but if anyone has any experiences or recommendations I would love to hear them. Her bike is an older Canadian made Peugeot UO18 for what it's worth. I've only been able to find one reference to this so thought I might seek some additional advice. I plan to remove the outer ring and use the 42 as a 1x. I can also use the trial and error method to see how the spindle "sits" on the square taper, however, would be good to have a starting point of ISO or JIS.

The final option is to just give up and try and re-sell it. I think the market for these might be kind of thin though. It's a great looking crank IMO, was fairly priced (assuming seller didn't know of the ofmega crank issues of course) so would love to find a solution.

Thank you very much in advance for any help provided!

I'm can also post this in the C&V section as well if that might be the best option.

JohnDThompson 

Older Ofmega spindles were narrower at the ends than other manufacturers, but that doesn't necessarily mean the arms will be incompatible with an ISO spindle. If you have a spindle you can test fit, give it a try:


Source: Sutherland's 4th Edition

squirtdad

ok I went through this a while back, so I hope this helps a bit

First, what is the Bottom Bracket on your wife's bike? English (68 mm width generally) or Italian (70 mm) This is important because the threading is different and you need to get the correct BB

Do you have a BB right now?

the 80's ofmega are basically campy clones, meaning ISO/Campy taper. (older ofmegas had a still different taper)

They also were setup to be used with an asymmetric spindle.

so fitting is a bit of a pain as result of all this fun

Per Sheldon brown :

"If you install an ISO crank on a J.I.S. spindle, it will sit about 4.5 mm farther out than it would on an ISO spindle of the same length.

Conversely, if you install a J.I.S. crank on an ISO spindle, it will wind up about 4.5 mm farther in than it would on a J.I.S spindle of the same length.

Theoretically, ISO cranks should only be used on ISO spindles, and J.I.S. cranks only on J.I.S. spindles.

In practice, you can very often get away with mixing these sizes, as long as you select a spindle length that gives the desired chainline. "

The big difference is that you don't get as strong a crank/spindle interface, as noted in the diagram previously posted.

As long as your wife is not a super strong rider you are probably ok, but may need to experiment with spindle length to get a good chain line.

itf6 

JohnD and squirtdad, the info is very much appreciated.

JohnD – That’s great info, and I was sort of planning to do this so the diagram will definitely help me along, thank you.

Squirtdad – Thanks for the feedback/info! To answer some of your questions, I do have a BB in there (cup and cone) and the shell is a 68 mm. There’s a Stronglight 101 crank on there now so the spindle currently in use is ISO but it’s 122 mm from what I recall (I will need to confirm though). I’m guessing that’s going to push the chainline out a bit too far? Definitely with a 1x set up? Sorry I know that veers off the rails a bit from the initial question. In any event, sounds like an opportunity to open it up for some maintenance anyway while getting the right measurements and figure out if it’s asymmetric. I’ll try to get an ISO but good to know JIS is also an option as well, if need be.

I guess I’ll be stopping off the co-op for a spindle. Thanks again for helping out!

(On a side note, digging through the spindle bin with a ruler and calipers looking for the right length down the mm, no pitting on the races and making sure you have an ISO/JIS taper, is as close to Zen as it gets.)