newb trying to figure out suitable bottom bracket replacement
 

I purchased a Schwinn Broadway from Costco on clearance back in November, and start commuting to work (10 miles daily, decent amount of up/down hills). The bottom bracket bearing just start going out, my LBN (local bike nerd) helped me pull the bottom bracket and we found water sitting inside. I live near Seattle and we get our share of rainy days during the winter, so I think this bike as built wasn't up to the task for commuting here.
Now I want to find a sealed cartridge replacement to swap in.

The spindle looks like the illustration labeled "Japanese Bottom Bracket Spindles, Traditional Cup And Cone Type" at http://www.sheldonbrown.com/bbsize.html. With my handy dandy ruler I measure it at 125mm end-to-end, and going off of that illustration it's about a=35mm, b=53mm, c=37mm. I wouldn't bet my life on these numbers, but they're pretty close. Especially the end-to-end measurement.
It has stamped on it what looks like VP followed by 3S. That page lists a 3S overall length as 121.5, so I don't really know what to make of that. Mine is definitely longer than this.

The outer diameter of the cup things that screw into the shell measures between 34mm and 35mm, so this seems to match the british/iso thread specs I see.

So after searching around this morning I'm thinking I need to measure the bottom of the bike across the bottom bracket shell to see if it's 68mm or 73mm.

I guess my question is if I find the shell length, the threading, and I know the end-to-end length is 125mm, am I ready to order or do I need more info?
I'm not really seeing a 125mm option. It sounds like going narrower could make the chain hit something, would I be safe with something slightly longer (127mm)?

This has been a bit overwhelming to home in on, so I'm not totally confident I'm going to order something that will actually fit. :)
Unfortunately my LBS didn't have anything in stock.
Anything else I need to worry about?
Thanks!

Shimano makes 122.5 and 127 mm spindle lengths for their sealed cartridge bottom brackets and one of these should work.

Is the spindle a nutted or bolt on spindle? when you removed the cranks, were they 14mm flanged nuts? or did you use an 8mm allen wrench to remove a bolt?
If it's a nutted spindle, measure to the end of the taper, not to the end of the nutted part.

You might want to bring the spindle to the shop and have them measure it to be sure. And for sure measure the BB shell. I suspect it's 68mm, based on where you bought it, at that pricepoint, and the brand. But you never know- measure 2x, buy once.

Ahahhh, I forgot about nutted spindles. They were indeed common on low-cost bikes.

An older design bolted spindle would also require a 14 mm socket to remove the bolt. The 8 mm hex head bolts are newer and usually limited to better quality cranks.

Assuming his VP bb is symmetrical.

it's a discontinued model with no specification from schwinn or on the costco site, so we can't confirm the size. Looking at the crank it could be a 122ish length.
measure from end of taper to end of taper. ignore the threaded nutted parts.

Less than 2 months for a BB should be covered under some sort of warranty I would think, but good luck on getting costco to come through. They may have a service plan but don't count on it. 10 miles a day 5 days a week for 8 weeks is ~400 miles.

Wanted to follow-up in case anyone else with this model comes looking for the same info. My local REI store had a Shimano UN54 127mm in stock so we gave this a try. It installed pretty well and seems to be about right. The cup thing that is not part of the main cartridge is made of plastic, but seems like it will hold up just fine. That plastic cup also protrudes from the shell a little bit (1 or 2 mm, I didn't measure) when in there as tight as we could get it, so maybe not the best option if you're big on looks. All I care about is getting to work so it's fine for me :)
The front derailer needed some adjustment after this, but now everything seems fit for commuting.

As far as the old one being symmetrical, I would say no if I understand the portion you are talking about. The "a" and "c" measurements were clearly a few mm different. I'm not sure that it matters tho as far as getting "something that works". :)

Thanks!
-a

The OP bought a bike that cost less than my cranks, minus chainrings. It'd be absurd to expect any sort of quality out of it. The bb - is worth about $5.

The plastic cup is SUPPOSED to protrude. If it doesn't, that means it's not doing it's job - the lip would be hitting the face of the bb shell instead of securing the cartridge. The plastic cup has a much lower torqure requirement than a steel/al cup, you WILL crack it if you try to apply standard torque to that cup. Take 30 seconds and think why a symmetrical bb of xyz length may not result in an identical chainline when replaced WITH a symmetrical one of the same length.

I have no doubt that the chainline has likely shifted, my hope was just that it was shifting away from the frame. This is why I went up a few mm rather than down. I read that shifting towards the frame could cause rubbing (seems intuitive), but shifting away from the frame seems fine if I adjust my front derailer. Is there another concern with shifting the chainline? As long as it basically works and doesn't cause frequent breakdowns I'll be satisfied.

I'm sure I could get a replacement under warranty, but I don't see why it would fare better than the original. I could certainly return the whole thing to Costco for a refund, but I don't expect I can find anything of significantly higher quality for less than ~3x the price. I might consider investing in a higher end bike if I keep up the commuting for ~6 months. Then again, I might not if this cheapo keeps chugging along. :)

if you measured the BB spindle correctly, a replacement BB should not affect the chainline. The Right side fixed cup normally is steel or alloy and should be installed so the shoulder bottoms out and is square to the BB shell. The chainline is not affected by the brand of BB you buy. a 121 length spindle is a 121 length spindle. The plastic 'adjustable' cup is normally tightened until it stops, torque measurements are not really necessary. If it sticks out a little or is recessed it doesn't really matter.

You'd be surprised at what you can find your LBS in terms of bikes. Craigslist and swap meets are also places where you can find decent commuter worthy bikes on a budget, but it requires more hands on knowledge and mechanic work to keep it under budget. Considering your BB wore out in less than 500 miles, I think the value proposition is not just a cheap price. If you pay a little more, things will last a little longer, and the bike shop is almost always going to be a better service resource than any big box for anything. What's going to crap out next? The wheels? Derailleurs??

I do hope you keep up the commuting. It's a fantastic way to get around- it's cheaper than driving, puts less miles on your car(s) and it also keeps you in better shape than driving to the gym.

Ahains, since you found water in there in the first place and you're commuting through our sloppy North"WET" conditions (and good for you!) I'd suggest drilling a drain hole in the BB shell if there isn't one there already. If your frame has the little plastic shifter cable guide down there do the best you can at providing a drain hole. And hopefully you or your LBN greased the inside of the shell to avoid ongoing rusting from the water that finds its way into the BB shell.

If you continue with your commuting I suspect you'll be shopping for a nicer bike sooner or later. Don't have any fear about justifying it. Just look at the cost of gas and a gym membership you're saving over a year of bicycle commuting :D

You don't actually work for velo-orange do you? Chainline IS affected by exactly what BB you have. You're telling the OP that every single bb out there is symmetrical, which is clearly false. Please stop providing incorrect information. A 107mm and a 110mm shimano BB would according to you, result in different chainlines. Which is _not_ the case.

I think he said chainline is not affect by the brand of BB you buy. Assuming the same spindle taper, if a 110m spindle is longer than a 107mm spindle, and I install the same crankset on each, wouldn't the crankset, and therefore the chain of the 110mm setup be located further away from the centerline of the frame?

Operator-
I do in fact work for Velo Orange.
A Shimano UN52 68x121 bb is the same axle length as a UN72 68x121 BB, which has the same specs as an IRD 68x121 bb, which has the same specs as a campag 68x121 BB. There may be some obscure BB's with asymetrical spindles, but those are kind of rare. The bike the OP is working on is new- made in 2008. I don't think it's absolutely necessary to bore him with a history of every single last BB spindle permutation.

Your last post sounds a little grouchy and reads like you are pissed that I am constantly spewing 'incorrect information', and 'falsehoods'. I'm fairly confident that much of what I spew here can't be classified as 'incorrect' or 'false', except in matters of opinion, politics, or women. I'm open to learning of course. Some of the weird **** that comonent manufacturers did back in the day baffle the **** out of me. But lets be real here- it's a 2008 Schwinn built in a factory in china with low end shimano parts and a chinese crank. Shimano has very specific parameters for optimum performance, even for low end bikes. That crank and derailleur will function best with a very limited range of BB spindles, and believe it or not, they are using actual new stuff that has the same spec from one mfg to another. I don't think it matters here what campag or Rene Herse did back in 1968.

So, please stop the H8n, yo.
What's next- punctuation errors?

Both you and operator are definitely people who should continue to post here. You're both way up on the knowledge and experience food chain, so remain active.

I hate punctuation errors

And operator- I never stated 'every single BB spindle is symmetrical'. I stated that a given BB spindle length is a constant, and will give the same chainline, across brands. A 121 is 121.

This is false.

For example:
Shimano UN54 68-110:
Overall length: 111.5mm
Length of drive side from BB shell: 20mm

Velo Orange Grand Cru 68-110(french):
Overall Length: 110.5mm
Length of drive side from BB shell: 22mm

This difference may not be significant, but it is a difference.

Disclaimer: Harris Cyclery sells VO french thread bottom brackets and other products. We like them.

I stand corrected.....
poo.