Bicycle Mechanics - bottom bracket advice

so im trying to convert my one piece BB to a three piece. i need it to be jis square tapered. this is for a schwinn traveler that i converted to fixed gear, so the chainline is important. i understand you cant say anything about it without knowing the width i need, but i just want to be set on the right path. ive been looking at these so far:

http://www.bikepartsplace.com/discount/bottom-bracket-bb-un54/
and
http://www.bikeparts.com/productinfo/FSA-Ultima-CrMo-68103mm-Square-Taper-JIS-BB-Shimano-compatible-22074-53050.html

any advice would help
thanks

Try reading this thread http://www.bikeforums.net/archive/index.php/t-201246.html

ps Or are you simply trying to get an idea of the relative quality between those two cartridge brands?

So it need to be JIS square tapered? Is this because the bottom bracke is JIS threaded or because the crank you want to use is JIS? I always thought the one piece astubula cranks required a special adapter to convert to any normal bottom bracket? Maybe you already have this part figured out, but I'm just checking. After you throw this in you can choose your BB and cranks?

From sheldon/harris cyclery site

http://www.sheldonbrown.com/harris/opc.html

Conversion Kits
If you wish to upgrade a bike built for one-piece cranks to use modern 3-piece "cotterless" cranks, you need a "conversion kit." This consists of a special bottom bracket axle and associated bearing parts that can be pressed into a one-piece-crank type frame.
TruVativ American-to-Euro Conversion kit
Out Of Stock

These beautifully machined aluminum bushings fit into the shell of a one-piece-crank bottom bracket, and are threaded to accept a standard threaded bottom bracket, normal 68 mm width. 3 long CrMo bolts connect the two bushings to one another for a secure mounting.

This saves weight, improves shifting, and allows the use of modern clipless pedals.

Be the first kid on your block to put a Dura-Ace crankset into your Schwinn Varsity!

Here is what you need
http://www.niagaracycle.com/product_info.php?products_id=10468
I just bought 2 and installed one on my crappy winter bike to add low gears, plan to switch it to every winter bike as bikes rust out after 2 or 3 years of winter biking in heavy snow and salt here in N Michigan, these are cheap too. It comes with the square taper ends and installs very easily. The chrome cups on my bike weren't removable so I left off the included cups.Niagara is good to deal with also. All you need is grease, but note one speed pedals are a narrower thread than 3 piece so order a set of pedals unless you have a spare set.

ya, i saw that thread. but i have the square tapered cranks, and some people i talked to said i would need JIS. isnt that different than ISO?

ya, i saw that thread. but i have the square tapered cranks, and some people i talked to said i would need JIS. isnt that different than ISO?

Yes
http://www.sheldonbrown.com/bbtaper.html

ive been looking over most of that stuff. so it seems that i need the conversion kit on sheldon's website and then i need to figure out my chainline and get the appropriate width in a square JIS BB, right?

ive been looking over most of that stuff. so it seems that i need the conversion kit on sheldon's website and then i need to figure out my chainline and get the appropriate width in a square JIS BB, right?

Your bb depends on the crank you're going to use. So do you have a threaded bb shell or not? The link I posted indicated you had a threaded shell, but it was for a Traveler III. Am not familiar with that model of Schwinn in any case...

Your bb depends on the crank you're going to use. So do you have a threaded bb shell or not? The link I posted indicated you had a threaded shell, but it was for a Traveler III. Am not familiar with that model of Schwinn in any case...

no, the shell is not threaded because its one of those old school ones. thats where the american to euro conversion kit comes in i guess

http://www.sheldonbrown.com/harris/opc.html

then any bb will fit in there i assume. then i get a square taper jis or square low profile depending on my cranks?

The JIS square taper BB is included in the conversion kit

Unless you are using a Campy crank or one of the rare Suguino Track cranks, your crank is almost certainly going to need a JIS taper.

and, as people have noted, the chainline depends on the crank you intend to use, and of course on the cog on your rear wheel.

thanks guys, i appreciate the help. im still gonna have to go to a shop around here so they can see the physical bike/crankset and have them look at it, but i feel like i have a better idea of what i need, so thanks.

^ Truvativ BB Adapter might be what you're after.

http://www.burkescycles.co.nz/product.asp?prodid=1527

That link is for a store in New Zealand, but you should be able to find this part closer to home.

.

You can just use a 3 piece bottom bracket crank adapter used in BMX bikes. It uses the bigger bearings with the smaller spindle. Relatively economical in the $20 range. Roger

^ Yeah, for a square taper in a commuter bike, that's probably all you need.

The Trivativ BB adapter is a bit pricey but is useful when you want to use ISIS drive BB cartridges or even the modern "external" bearing BBs like the howitzer or the Shimano XTs - on a frame with a 3-piece style BB shell.

.

I am not at all sure the adapter on Sheldons site is what you need!

I wanted to do the same as you, bought a similar adapter from UK and it is too big. Had this problem for more than a year now and can not understand why they can not give more info on these things.:mad:

My bikes (5 at present) has got the one piece crank like yours, but the BB housing is smaller than BMX but bigger than standard modern.

Had this problem one year ago on another bike, yet another type. Cottered cranks that one. Why not tell us what we need?? 68 x ?? x spindle lenght or 70 x ?? x spindle lenght?? Do they not want to sell?

What I did three times now: Got a bike with ok BB from the dumpster. I use alu frames for low weight. Cut the two chainstays, the down tube and the top tube close to the BB shell using an angle grinder.

Using the grinder you "shawe down" the size of this housing until it fits in your BB.

Use Epoxy to "glue" it in there. Make sure it is the right way (drive side on drive side). Leave to dry.

This is what I had to do, but not what I wanted to do.

There must be millions of older bikes out there needing a new BB. Why is this so difficult? I am sure there is some sort of solution(s) awailable, but only if you are good at guessing! :mad::mad: