cottered crank to square taper conversion concerns need help?
 

I am converting a cottered crank to square taper I am having difficulties with picking right size. Here is the information: have 73mm enlish thread bb she'll with inner 33.4mm width, and a 145 mm spindle. My question is about the length of the spindle. Does the length of the spindle I buy really affect the chain alignment? And also what product possabilities do I have

Yes the length totally effects chainline. The spindle length is will be determined by the crankset. Is this a SS, IGH or derailleur set up?

It's a front and rear shimano 600 derailleur with friction shifters

What bike had cottered cranks and a 73mm shell? I was of the mind that the 73mm shell only came up with mountain bikes in the 80s. I don't think I've ever seen a mountain bike with a cottered crank.

Was thinking the same thing

Yeah those numbers don't make sense it should be something like a 68-70 maybe 72.

I am going to check again. It's a wonky bicycle that I bought. I am pretty sure it's 73

Why don't you tell us what the bike is?

Or better yet, post a picture.

Don't Raleighs have wider than usual bottom bracket shells? With that in mind, I'll speculate that's what we're talking about here.

Cotterless spindles for Raleigh shells do exist, but they were never common and have become prohibitively hard to find. You can cut the shell down and tap the threads to standard (Raleigh shells are not standard) and go cotterless, but when you add up all the work involved, cottered cranks become pretty attractive.

It is a Galaxy Par exellence. from south korea i speculate its a early 80s late 70s bicycle. Measured the bottom bracket with a digital vernier caliper so I am sure it is 73mm. Very rare. nothing fancy probably a low end korean bicycle had falcon parts on it. I have upgraded everything. The only thing left is the bottom bracket. I

Over tapping the Raleigh thread to the english standard is pretty straight forward. Shimano UN72's come in 73mm with different length spindles so you wouldn't have to cut the shell.

what about the spindle length. would you happen to know if they sell such lengths in square taper

Most mountain triples start in the 120mm spindle length range. You'll have a much better chance making a long spindle work than a shorter one where the crankarms hit the chainstays.

It really depends on the cranks, but I doubt you'll have issue with anything 120mm or longer.

Thank you so much. whould it help if i added more spacers on the freewheel side of the rear wheel

I believe they go to 122.5 but as IthaDan says the crank/chainring will determine fit. I think you can make it work.

Thank you everyone for the advice. this is my first post ever. I will let yalll know how this project goes in regard to the conversion

Man - The numbers sound all off - Better recheck it - Especially your D and B measurements...

http://sheldonbrown.com/bbsize.html

Then look at: http://www.amazon.com/AXLE-5S-B-ROAD.../dp/B0047106NO

i have a 70s zebrakenko that i converted from cottered to square taper. i used a 90s shimano dx crankset and bb. the bb is 122mm, i didnt have a problem with chain line or crank arm clearance. what i did have a issue with was the bb cups that came with the dx wouldnt screw in enough to tension the spindle, rather then mess with spacers i just reused the existing cups. this may help your issue with shell width, use the existing bearings after a regrease if they are still good or just pop in the new ones as i did. i like this because i could have a caged bearing set instead of loose bearings. im not sure if this will solve your problems ir even work in your application but i thought id throw out a different opinion. you can also measure the existing cottered spindle and then search for a crankset that uses a similar width in square taper. hope this helps.

The Shimano UN55 comes 73mm in several lengths and should work for you. The length will depend on crank and set up most likely 118 for a double and 122mm for a triple.

http://www.amazon.com/Shimano-BB-UN5...bottom+bracket