Bike Forums - View Single Post - Replace ofmega 70 x 118

07-11-14 | 02:03 PM

#5

squirtdad

Senior Member

Joined: Jul 2006

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From: San Jose (Willow Glen) Ca

Bikes: Kirk Custom JK Special, 86 De Rosa Pro, '84 Team Miyata,(dura ace old school) 80?? SR Semi-Pro 600 Arabesque

Quote:

Originally Posted by Bianchigirll

A lot of these Ofmega BB/cranks had a unique taper. Again check Sheldons website.

Some one makes adaptor rings for changing a Italian thread BB shell to English but without the correct tools and locktite I wouldn't try it.

Quote:

Originally Posted by onespeedbiker

"Ofmega cranks, including those branded "Avocet" use a non-standard spindle, thinner than either J.I.S. or ISO spindles. As far as I know, nothing else works". Sheldon Brown's Bottom Bracket Size Database

I believe all the Ofmega cranks/BB have the Ofmega propitiatory square taper, (I will update velobase). As mentioned earlier there is no point switching to a different BB as it will still need to be Italian. As mentioned the only way to properly tighten the fixed cup of an Italian BB is with a BB tool

Amazon.com : Park Tool HCW-4 Box End and Pin Spanner Crank Wrench (36mm) : Bike Cranksets And Accessories : Sports & Outdoors and $17.40 would certainly be a good investment.

If you must get a cartridge style BB you will need to switch the crankset also..

fwiw

I spent a lot of time on Ofmega crankset and bottom bracket research and experimentation when I was given a 'free" torpado super stradaa couple of years ago.

At best there is a lot of mystery and uncertainty including on velobase.

this is my understanding (which again is based on research of a voodoo subject and some personal experience)

Early Ofmega cranksets used a proprietary taper. The problem is no one can define exactly what early/old means. to quote sheldon "(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.)"

The ofmega cranksets from the 80's (again not precise) think competizone and CX (at least I hope CX as I just ordered a set on ebay) were essentially campy clones with ISO taper and they used the asymmetrical bottom bracket (118.5 mm spindle) like campy records did. The Mistral may be different

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