How do I figure out what BB I need?
This is my first post here, but I have been doing lots of reading and learning already. Great forum here. You've all already been a great deal of help, so thanks in advance. Anyway, onto the task at hand. Here's the story.... I bought a used Schwinn LeTour (late 80's vintage) a month ago, and have been doing some road riding on it. I love the old bike, and have been fixing some of the minor issues with it. I noticed that the left pedal was getting a little "crunchy" on my last ride. I figured that the bearings in the crankset were probably toast. I went ahead and tore everything down. The bearings were pretty dirty, and felt like they had some grit in them. They also appear to be a rather old style, as I expected.
I want to upgrade to a sealed cartridge type bottom bracket. Unfortunately, I'm not sure what I need to buy in order to make it work properly. Here's what I do know about the Le Tour.
-The Schwinn frame uses a 68mm English type
-The cranks are Sugino VX 170mm
I can measure other stuff if someone can clue me in on how this works, and what I need to know in order to buy the correct bottom bracket. I'm thinking that something like this may be what I need?
Does my replacement bottom bracket HAVE to be Sugino brand, or can I use something else? I have attached some pictures of my bike, and the collateral damage for reference as well.
You have to match the overall length of the spindle measured between the ends of the square tapers. Ignore the threaded stubs at each end of your current spindle. I assume your current spindle has JIS tapers which almost all Japanese made cranks do. English threaded bottom brackets 68 mm wide are very common so matching that is no problem and Shimano makes a wide variety of sealed cartridge bottom brackets that should work fine.
I am rebuilding my old 1987 Schwinn Super Sport. The original bottom bracket (cup and cone style) are basically no longer available so going with a cartridge style is the only practical and cost effective method. (Realize you could easily clean the old BB and replace the ball bearings, but it'll be hard to find spindles or cups/cone for it).
You've already figured out half of the specs: 68 mm width.
Next, you'll need to measure the overall length of the existing spindle, or often the length is marked on the spindle.. Note, the Sugino BB pictured says 103mm and 68mm, and this is shorthanded to 68x103.
Two other dimensions are critical, the threading and type of crank arm taper. Seeing you have a relatively common bike, the threading and taper fall into the 98% category.
Regarding threading, see and scroll down to "bottom bracket":http://www.sheldonbrown.com/gloss_bo-z.html
You'll also need a bottom bracket tool to interface the cartridge. If you want to know a bit more, see and scroll to Bottom Bracket Tool Selection http://www.parktool.com/blog/repair-...ottom-brackets.
And there is always a hot debate of whether to grease the spindles before attaching the cranks. I do, but some warn against it. It becomes a lively debate at times.
The OP already established the threading is English and the probability of the tapers being JIS approaches 100%. The only ISO tapered Suguino cranks I've ever heard of are Track cranks and this certainly isn't one.
Originally Posted by MudPie
Ok, I'll order one of those cartridge install tools also. Definitely don't have one of those in my tool box.
Ignoring the threaded ends, the spindle appears to be somewhere between 119mm and 120mm depending on where I measure. The square ends aren't completely flat, so there is some room for interpretation. The only numbers that see on the spindle are as follows: 3P G-10 B. Is that of any help?
Will I be able to reuse my old cranks with the new cartridge style bottom bracket? I was thinking I could just use an appropriate bolt instead of the original nut.
DRF aka Thrifty Bill
Not so. You can buy cup and spindle bbs for Japanese bikes all over the web, pretty cheap, and also for that Schwinn Super Sport. But you can also buy a UN-26 Shimano cartridge bb on line cheap. When replacing a bb, I almost always go with a UN-26. They cost about $10. Piecing together a cup and spindle bb will cost at least that much, if not more.
Originally Posted by MudPie
But on the other hand, the old cup and spindle bbs are very durable. 90% + of them that I find are OK, just need grease and bearings.
A lot of spindles were asymnetric. So you may need spacers to install it. Measure carefully.
Last edited by wrk101; 09-11-11 at 08:36 PM.
Will the Shimano UN-26 work with the measurements that I posted above for my Schwinn Le Tour?
Thanks, I thought I did thorough search but obviously not. I did find some spindles but they weren't cheap, and thought all were basically custom by now. I'm hoping to keep the ol' Super Sport as original as possible, with the Shimano 600 downtube shifters, brakes and der.
Originally Posted by wrk101
For the most part. You'd have to choose between a 118 and a 122.5mm spindle but you will have to do that for most brands of cartridge bb.
Originally Posted by Glazedham42
So is it better to get a cartridge with a spindle that is 2mm too short or 2mm too long? What is this going to effect in the long run?
If you do get one with a different length it will push your chainring that much closer or farther from your frame. At the very least it will make your shifting a little harder to tune. It may also cause cross chaining problems and in the worst case actually cause your crank to bottom out when you are trying to tighten it down.
Originally Posted by Glazedham42
In your pic I see crank arm fixing nuts that fit on a threaded extension from your spindle. The threaded ends should not be included in your measurement. With a catridge BB you will need crankarm fixing bolts that screw into a threaded cavity inside the spindle. It also appears your spindle is asymetrical. If you look at the chart at the top of this page for your 3P it indicates a 122mm is the correct replacement:
If you have an lbs near by you should be able to take your spindle in and have them order you a match in a sealed catridge unit. You also might try posting this in the Classic & Vintage forum as those guys should be more used to this issue.