cottered bottom bracket

ewanm77

MacRetro Rider
im wanting to replace my cottered bottom bracket with a square tapered cartridge one
I have no idea what threads are on the frame or how to go about finding a replacement
the axle I took out is 145mm long and the bb hole is 34mm diameter
 
Re:

Replacing your bottom bracket should not be a problem. The measurement you provided is a bit odd, could it have been 35mm? that would point to French thread. You could also measure the bottom bracket shell width, 70mm is Italian, 68 is most likely English. Best bet is to take it somewhere, like a bike shop, where you can try different BBs.
 
Re:

I got a square taper bb in today to make sure it would fit. Just need to order one with the proper axle length and get a few cable guides
guides.
 
If it's a singlespeed then you need to get the chainline straight. Normally when you buy a crankset for singlespeed/fixed/track use it'll tell you what width BB to use to get a 41mm chainline. It's usually 110mm for track chainsets using the Shimano taper.

If it's not a singlespeed then the chainline isn't critical. You want to aim for the chain to land in the middle of the cassette so that you're not cross-chaining all the time. 113-115mm usually does this.
 
its a double that's going back onto it going to be a 10 speed maby 12 depends if the shimano eagle will run 6 speed ok. the original spindle was 145mm long I put a 112mm I had in and tried a old crank set and the inner ring was touching the chain stay was thinking about a 122mm one
 
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