Kommisar89

Here's a question I haven't seen posted before. I'm curious about Ofmega crank, bottom bracket and spindle compatibility. Since my old bike had an Ofmega crank I bought one off eBay recently for my project. And it just so happens that the frame I found has an Ofmega bottom bracket installed. So all was well with the world until I happened to be reading Sheldon's page on spindles and noticed he mentions that older Ofmega cranks used a unique taper that is not compatible with anything else. Well, both my new crank and my new frame with the bottom bracket are still in transit so I can't try them out but now I'm worried. The crank is the one shown below. I have no idea what model or year it might be so I'd like to learn a little more about it. Does know anything about this?

RobbieTunes

I have an '85 Ofmega crank, came with an Ofmega bb, also. Yours definitely predates mine, which is Campy square taper compatible.

John E

Old Ofmega should match old Campagnolo.

Kommisar89

Yeah that's what I was thinking. My fingers are crossed. But who wants to bet against Sheldon Brown?

Charles Wahl

Well, Sutherland's thinks that "older Ofmega" is one of the smallest spindle-end types: See in the middle of the excerpt posted here.

tashi

Uh oh, I just slapped a mid-80's 600 crankset on a BB that was paired with an Ofmega crank. I haven't ridden it yet, so I don't know if it'll work. The BB wasn't marked with much though, except for the cup sizing info and the letters *** (really!). Am I screwed? It does seem to sit a little further inboard on the spindle. Hmmmn.

cudak888 

This one?

https://velobase.com/ViewSingleCompon...m=119&AbsPos=0

Aluminum cups on those, if I recall right. Known for jamming in steel frames if not greased.

-Kurt

tashi

That looks right. So, assuming that the spindle wasn't swapped out, it's ISO and should be good with my 600 crankarms right?

I can probably find this out on sheldon's site, but is there and easy way to measure what standard the spindle taper is?



Edit: sorry for the derail, I just thought I'd jump on this Ofmega thing right away.

Kommisar89

Arrrgggghhh!!! My head is going to explode!!! But thanks Charles. So I wonder what exactly constitutes "older" Ofmega cranks? I'm going to bet that mine are "older" since they resemble Nuovo Record clones (and I purposely picked those) instead of Super Record or much more modern 80's styles that resemble Campy Victory cranks. I guess we'll see if the spindle works with the cranks. Or it'll be back to eBay to find a spindle.

Kommisar89

No problem man, we're all here to learn and maybe sometimes educate

cudak888 

In other words, an Ofmega crankset on ISO taper would be a safe bet, but not the other way around.

-Kurt

P.S.: To what extent is this splitting hairs? Has anyone done a study to see what the differences in in overall crankset seating on the spindles?

Kommisar89

Probably so with just a little extra Q factor. We shall find out. Send me some of your cranksets and I'll channel Frank Berto and do the tests. The cranksets might be destroyed in the process however

cudak888 

Seriously though, I've been tempted myself. I'm sure there is a slight variant between cutoffs for, say, the various manufacturers of JIS tapers for one; secondly, once seated and tightened down, does a significant enough difference in seating (whether mismatched JIS to JIS, ISO to ISO, or JIS/ISO or ISO/JIS) to cause a problem?

Then there's the amount of torque and whether the spindle is greased or not before installation...

-Kurt

tashi

Well, as usual, Sheldon covered it:

"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.

Confersely, 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.

Taper matching was fairly important back in the day of loose-ball cup-and-cone bottom brackets, because these required regular maintenance/overhauls, and this required removal of the cranks. Every time you remove and re-install a square taper crank, the hole in the crank is liable to get very slightly larger.

This was particularly an issue when using J.I.S. cranks on ISO spindles, because over time, as the crank went on farther and farther, you could run out of taper, and the square end of the spindle would become flush with the surface the crank fixing bolt/washer pushed against. At that point, further tightening of the bolt won't make the crank any tighter, since the bolt is bumping onto the end of the spindle.

These days, however, most folks are using sealed cartridge bearing bottom brackets. With these, there is no routine maintenance required, so typically the crank will be installed once, and will stay in place unless/until the bottom bracket needs to be replaced. This greatly reduces problems of wear to the interface.

I generally avoid mixing sizes on customers' bikes, but I have a lot of experience mixing ISO/J.I.S. in both directions on my own personal bikes, and it as never given me a lick of trouble. "

From:
https://sheldonbrown.com/bbtaper.html

So there it is. They both work with each other. Pretty much. I'm going to stick with the 600 (JIS) crankarms on the ISO spindle 'cause it looks like it'll work pretty well as it sits pretty far on the spindle but with plenty of room before bottoming out. I think. We'll see after some miles and fixxy trix (just kidding).

Oh, and there's this, also on the same page:

"(Note: Old Ofmega/Avocet spindles were quite a bit skinnier/longer even than ISO. There are no modern bottom brackets that work with old Ofmega/Avocet cranks.)"

So, Komissar, you might be SOL if the BB your cranks are old Ofmega and your BB is new Ofmega.

mkael

Interesting.

Is Ofmega still in business ? I am under the impression they folded only a few years ago? I am unable to find their site.

I have one italian bike from the mid 90's. It came with Ofmega everything. The bb said 'JIS axis'. Anyone know anything about this bottom bracket? JIS on italian bikes seems strange to me. I think that is a Ofmega bb because searching for pictures get similar looking bb's.

Charles Wahl

I think between Sheldon Brown's 4.5 mm and Bob Barker's 6 mm, it's pretty safe to assume that it's not splitting hairs so much as millimeters. Since the difference in Q-factor varies as arctan (2 degrees) -- a factor of about 63 -- the actual difference in spindle end size for different standards is very small! However, given the number of people who report interference problems when installing replacement BBs, it's not insignificant. Going the other way, I guess the only concerns about using a slightly larger spindle end are chainline, Q-factor (spread between pedals) and how much purchase the spindle has on the crank socket (whether you're comfortable with that).

Phil Wood (the nec plus ultra of replacement spindles) appears to make two different spindle sizes: ISO and JIS; that seems to cover things for them. If I were replacing a BB and wanted to put a smaller socket size crank on a larger spindle-end, I'd first be looking for a spindle slightly shorter than the original -- maybe the difference between "road" and "track." And I'd definitely torque down the drive-side, check clearance at chainstay and chainline, and then remove the crank bolt to see how far the spindle end is short of the crank bolt washer seat on the arm. On any crank, there should always be some space, so that you know the washer is seated on the crank arm seat, and not on the end of the spindle. With a larger spindle end, the problem would be too much (not enough purchase of spindle on crank socket) -- any more than 5 mm would worry me, unless the crank socket were particularly deep!

Do note that some spindles also have longer taper ramps than others! If memory serves, JIS standard has longer taper (but maybe I have that reversed). So another mix-and-match problem to watch for is whether your crank socket has climbed to the end of the taper.

unworthy1

just to muddy things a bit: I have never seen that model Ofmega crank before, and it appears "early" to me and not as Campy-like as some I have owned (even though it may be 144BCD), it also looks like a swaged-on spider, but I'm guessing that. I have never had any fit issues with the 3 models of Ofmega cranks I have owned using Campy NR-era BB spindles (whether that's called ISO or something just Campy-specific). Those styles are the "Super Competizione" and "Master" and the one sold as an Avocet Triple...YRMV

Kommisar89

Yeah I think it does look swagged. The choice of this particular crank was dictated by the need to find a crank that would be appropriate for an entry to mid-level Italian bike of the mid 70's. The original Ofmega crank on my bike looked a lot like the one in this picture (maybe exactly like but I can't remember now). I didn't go with that because A.) I didn't want to go cottered and B.) I've never seen a crank like that anywhere besides my bike and this picture. The one I bought on eBay appears to be from around the same time period and maybe was the next model up in Ofmega's catalog, who knows. I also like that it has "Nuovo Record" style rings with the oval cutouts more or less while all of the others I've seen have the "Super Record" style rings. I guess we'll see where this goes when the parts arrive.

JohnDThompson 

I run an Ofmega (Avocet) triple on a JIS spindle with no problems.

cudak888 

According to OFG, the old tapers are supposedly small enough that nothing is compatible with them.

-Kurt (Off to Velobase to raid the image archives for Ofmega BB spindle photos)

Kommisar89

I think I checked the 'base but all of the Ofmega BB spindles said ISO. That might be true for those models or it might be a bit of confusion. I just went back and checked the Campagnolo spindles and they all say ISO as well but according what I'm finding out now, that might not be true either if Campagnolo had their own proprietary standard.

With this much confusion among those of us who are reasonably knowledgeable about this stuff I shutter to think about finding the correct spindle on eBay. Figure the odds that the eBay seller is going to know whether his Ofmega spindle is old proprietary taper or new ISO taper. Or is it really even ISO taper anyway? How do we know that the later Ofmega spindles aren't using Campagnolo proprietary taper? Maybe that should be ISO - Italian Standards Organization. Man this is a mess.

Charles Wahl

I've never been able to track down who first quipped,
"The great thing about standards is that there are so many to choose from."
I heard that it was from the computer industry.

Kommisar89

Well the crank arrived today. Here's the good and the bad. First the bad. The Ofmega spindle (which actually came with the frame) is trashed. The Bearing surfaces are badly pitted. C'est la vie. Now the good - it's not some weird ultra skinny Ofmega/Avocet proprietary taper. I pulled out my 2002 Veloce crank and spindle to compare. They're the same. Same narrow end, same big end, same taper. So I believe that means it's ISO. That should make it easy to find an appropriate replacement even if that turns out to be a modern Campagnolo cartridge bottom bracket.

rideone

i'm currently dealing with the same issue as OP and I am lucky enough to have a few different spindles on hand to compare. I've got the exact same crank and original BB taken from an early Colner. I also have another Ofmega BB with different cups, but a similar spindle, and also taken from another Colner, . Unfortunately both spindles are badly pitted so I'm looking for a replacement.

I measured the tapers today with digital calipers and while I don't have the exact numbers off hand (i'll report them later, but i think it was like 12.3x mm), the Ofmega taper was definitely smaller than Gipemme, Zeus and Campy NR. Eyeballing how far the crank went on the non Ofmega spindles showed about a 2-3mm difference. That isn't much at all. I have good reason to believe that with older Ofmega cranks you could get away with using Gipiemme or Campy spindles. Sadly the Gipiemme spindle is also pitted (!), the Zeus is NOS and a weird width any (stamped 55) and the NR is for 68mm. So, my search for something compatible continues!

Chombi

It might be too late now, but did you also consider looking for a Gipiemme crank for your project bike?? Gipiemme pretty much occupied the same "mid tier" level as Ofmega did as manufacturers of Italian components and should also fit in with you mid level bike build intentions. I don't think you have to deal with too many issues with sizing either with the Gips, plus they had some very nice looking cranks back then that look much better than what they cost.

Chombi