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Discussion Starter · #1 ·
I have a mid-80s Gitane Tour de France frame that has an ofmega 34.8 x 24 F.s bottom bracket 68mm x 110mm long axle. This will not work with the crankset and cassette I'm trying to use because the axle is not long enough. I have not been able to find a longer axle on ebay for the 68mm yet.

I want to know if there is a more modern bottom bracket bearing that will fit this frame that has an axle length of 120mm.

Thanks for your help.
 

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French thread standard is 35 x 1, which is what it looks like your Ofmaga is. You will need a French thread BB in the axle length and axle taper (assuming square taper) to match your rank. Pelo Orange is usually a good source for modern cartridge BB for this older stuff.

 

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I don't know if you looked at the Shop | Soma Fab Shop but they have IRD bottom brackets in 118 & 122mm and French conversion cups. The QB-50 BB and the conversion cups would run $60. Or you could go with the QB-95 and the French cups for about twice that.

I've got two of the 95's with about 40,000 miles between them and they're both still rollin'. I pressed new bearings in the 1st one at 20-25,000 miles but that was pretty pain free.
 

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Discussion Starter · #6 ·
That is a nice source velodog, thanks. I'm having a hard time understanding how the conversion cups would work. Doesn't appear to be enough room down there for additional cups. Also I see the QB-55 but no QB-50. Amazon has the QB-55 for a few dollars more. I only mention them for how extremely easy it is to return Amazon items around here. They don't have the conversion cups.

Is it possible to switch axles? Ebay doesn't have any Ofmegas long enough for my use. Do people switch axle brands?
 

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That is a nice source velodog, thanks. I'm having a hard time understanding how the conversion cups would work. Doesn't appear to be enough room down there for additional cups. Also I see the QB-55 but no QB-50. Amazon has the QB-55 for a few dollars more. I only mention them for how extremely easy it is to return Amazon items around here. They don't have the conversion cups.

Is it possible to switch axles? Ebay doesn't have any Ofmegas long enough for my use. Do people switch axle brands?
QB-50 was a mis-type by me, shoulda been 55. The cups would be removed from the BB and replaced by the conversion cups. That's why the 55 is the better choice for the conversion than the 75, the 55 has steel cups is why it's cheaper than the 75 and the cups would be replaced by the aluminum conversion cups.
Typically the non drive side cup is removed and the BB is put in from the drive side and then the non drive side cup is secured. With the conversion cups both of the English threaded cups are removed to be replaced by the French threaded ones.

I saw Vintage Ofmega Bottom Bracket 121mm | eBay

2nd hand and may or may not be rough. I would think that you could switch out the spindle, but I'm not 100% positive.
 

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Discussion Starter · #8 ·
Thank you for that very clear explanation, velodog. That would be the way to go.

I saw that ebay item but didn't want to pay the price but with an offer I may be able to buy it cheaper than the QB-55 and conversion cups.

The problem I'm trying to solve is that the shimano Exage crankset I wanted to use as a 2x hits the frame with 113mm Ofmega BB. I am proceeding with the project as a 1x using an Action 4 bolt crank but I don't think it will climb the way I need it to around here for me and may revert to the shimano 2x with one of the solutions you have helped me find to lengthen the spindle and clear the frame.
 
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