Originally Posted by
squirtdad
note the taper varies and there is no definitive guide. some are unique, some are ISO, some require an asymmetrical spindle like campy so getting the correct BB can be a huge pain...
Valid observations! If anyone is bored enough, and had the time to spare, here’s some long winded observations of my own which may or may not prove helpful to others who have banged their head against the wall around the subject...
I purchased a Super Competizione for use with an Italian bottom bracket shell. This was before I realized that determining which bb to use would be such a pain in the butt.
In my quest to figure exactly which bb to to use, I’ve only been able to discover that information is scarce, and unclear in its vagueness. Here’s what I’ve found:
Ofmega is known to have used a uniquely proprietary taper as previously mentioned. This taper is said to be skinnier than other tapers, and apparently attributed to “earlier” Ofmega cranks. The problem here is that there seems to be no guiding factors that identify exactly what “earlier” means, or how to differentiate “early,” from “late” cranks.
Also, if we assume that the later Ofmega cranks which utilize a more common Campy NR/SR style taper are post ‘78, it seems that the spindle length needed for a Competizione is longer than that of its Campy counterpart. According to Velobase, a Super Competizione spindle for an Italian bb shell is 119.5mm, while a Campy NR/SR would take a 115mm spindle.
Making the challenge greater, is the relative scarcity, and expense of Ofmega bottom brackets to experiment with. Most I’ve found over a long search, are on eBay from overseas sellers. I’ve located a couple in the 119.5mm length, but usually the longest spindles available are 118mm. I’ve been scared to buy any of them since they’re expensive, and there’s is no way of knowing which taper I’d be ending up with.
I’m assuming my crank to be “later” Ofmega, since the Super Competizione group was available late 70’s to early 80’s. That said..,
My solution? I’m not entirely sure it’s a problem solver yet, as I haven’t finished the test fit, but I’m taking a gamble on a Dura Ace 7400 bb. The 7400 has Shimano’s “low profile JIS” taper. It’s designed for use with Campy NR/SR cranks. It’s a short spindle at 70-w-113mm, but for whatever reason, it seems to be working. Final torquing of the fixing bolts, and chainline adjustment if needed, will will be the ‘make it or break it’ revelation of course. I’ll be thrilled if it works, and if it doesn’t, I’ll be shelving the crank for something more straight forward.
Here’s the Super Competizione seated tight to an Italian 7400 spindle, but not yet torqued all the way. I predict when finally torqued, the crank will move another millimeter or so inward towards the chainstay. We’ll see how it goes:
