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Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

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Old 04-25-07, 11:26 PM   #1
noahjz
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Bottom Bracket crank compatibility MADNESS!!!!

I recently purchased for cheap an old Peugeot frame, probably a U08, that came with bottom bracket installed. I took it out to have a look and to grease it up... the spindle and the bearings are still in good shape so i thought it would be fine to keep using. So far so good but now I am pretty ultra confused about how to find the correct cranks. It seems more often people decide on BB based on the cranks they want, rather than they other way around, and that does make sense since the BB seems a lot cheaper. I just want to make a determination if this BB will work with the cranks i want.

ANYHOW
My BB is 68mm wide (good so far)
and the spindle length is 126 mm... that seems to be longer than most.
When companies refer to BB sizing is it the spindle length that they are really referring to? Is it fair to say my BB is 126mm?

I was thinking about getting something along the lines of the Sugino RD 165mm crankset Sheldon Brown suggests:
http://www.sheldonbrown.com/harris/c...30-single.html
I guess for another $30 I could get that matching BB that would definitely work with this, but it would be nice if the old one would fit.

I haven't been able to really nail down any solid info on how to determine if a certain set of cranks will fit a certain bottom bracket. My BB is square tapered, and I understand there are basically two camps, divided by Asian vs. European? So assuming my Peugeot has the original BB in it, it seems possible that Japanese cranks might not work with it?

Furthermore since eventually I am planning on making this a fixed gear it seems like having a 126 mm BB could result in chainline issues? Beats the **** out of me.

Please correct my rampant errors, misunderstandings, pathetic attempts at comprehension. Sorry I am such a DUNCE and RANK AMATEUR and PUERILE NOVICE etc etc. Thanks in advance to anyone who can clear up some of my confusion.
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Old 04-26-07, 03:03 AM   #2
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The BB axle length required depends on the cranks used. Older cranks generally needed longer axles. You want to use new cranks you need ...
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Old 04-26-07, 04:18 AM   #3
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BB sizes are referred to like this

1.37" 68x126 Square taper.

That is all the pertinent information you need to know. First item is the 1.37 which refers to the threading, second is BB shell length, third spindle length then finally the type of interface.
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Old 04-26-07, 06:54 AM   #4
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If you want to use that BB, you need to find a crank that works with that 126 mm spindle. That said, I suspect you could get other cranks to work as well. Since a new cartridge BB in the correct size will be about $25, I'd say get the cranks you want, see if you can get the chainline right with them, and if not, buy a new cartridge BB.
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Old 04-26-07, 07:00 AM   #5
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Welcome to the French bicycling world. With a Pug, you need to determine what threading you have before you make your next move. You may have French threading, you may have Swiss threading, or if the frame is from later than sometime in the early 80's, you have English (which I doubt).

Do the cups have any markings like 35*1? If not, we'll try the next step.
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Old 04-26-07, 07:01 AM   #6
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There is also the issue of the taper... whether it is ISO or JIS. The Sugino cranks are most certainly JIS, while the old BB in a Peugeot may well be ISO or something.

You can get a new good quality Shimano BB for less than $20. It would probably save you some pain and suffering to do that (although you can have pain and suffering with a new BB too... see my other thread )
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Old 04-26-07, 07:15 AM   #7
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Your OP is a pretty good summary of the situation. Yes, cranks define the needed bottom bracket length and taper and the frame threading defines the needed bb cup configuration.

I agree that you should spring for a new cartridge bb to match whatever crank you choose.

Check the current bb cups for engraving. If they say 1.37" or 1.37x24tpi or "BS" you have English threading which is a big plus as they are by far the most common. BTW, when you removed the current bb, was the drive side cup left-hand threaded? If so, that's also characteristic of English threading as is the 68 mm bb shell width.

If they say 36 mm or 36 x 24tpi you have Italian threading which is right-hand threaded on both sides but the shell width is normally 70 mm. Italian threaded bbs are fairly easy to find.

If they say 35x1 mm they are French (right-hand threading both sides) and are hard to find. If they have the same dimensions but the ds cup is left-hand threaded they are Swiss which is REAL hard to find. Both French and Swiss use a 68 mm bb shell. Good luck if you have either of these.
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Old 04-26-07, 09:39 AM   #8
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french v. english threading

vpiuva: I do not see any 35x1 markings on the cups. I haven't been able to get the fixed cup off yet (my LBS doesn't seem to regularly carry the right wrench). I'm trying to borrow one, but this could take a while. Are there any other indicators of threading type which i would be able to see with the fixed cup on? Thanks for your help.
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Old 04-26-07, 06:47 PM   #9
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So you have the adjustable cup out? Did it have a lockring? If so, see if will thread on any english BB your LBS has in stock. If it does, you're English. If not, probably French, maybe Swiss. If for some reason the lockring slides over an english BB w/o engaging, someone has rethreaded the BB Italian (was done on one of my French frames). If no lockring, you can still compare the cup threading to an english cup. Just try to mesh them together. Go=eng, no go = not.
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Old 04-26-07, 07:02 PM   #10
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Quote:
Originally Posted by operator
BB sizes are referred to like this

1.37" 68x126 Square taper.

That is all the pertinent information you need to know. First item is the 1.37 which refers to the threading, second is BB shell length, third spindle length then finally the type of interface.
True in the world of symmetrical axles. For asymmetrical axles you also need the offset. And a calculator.
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Old 04-26-07, 07:13 PM   #11
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Thanks everyone, that was a lot of informative advice, I have a lot of new things to try... I appreciate the info! vpiuva, I will take the lockring into the store tomorrow and see what works
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