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I just bought a 1970s Peugeot Mixte UE-18 for $10 at my local bike co-op. It's in great shape, but is missing the bottom bracket and cranks. I'd like to upgrade to a cotterless crankset. However, I don't know how to measure the chainline without cranks installed. I was thinking of getting these BB cups (with French threading) and finding a spindle of the right size. How do I figure out the right spindle length? Has anyone encountered this issue? Am I going about it the correct way? I would just like to keep the cost of the bottom bracket under $50.

Thanks in advance!

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You can measure the chainline at the cassette as well as at the cranks.

Park tool Company has a nice article on measuring chainline at both the crank and cassette.

https://www.parktool.com/blog/repair-help/chainline-concepts#article-section-3

It's my understanding that bikes sometimes have the chain further offset from the frame centerline at the crank than at the cassette, to avoid the chain rubbing on the next bigger ring when small ring - small sprocket cross-chaining (triples especially).

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Sheldon Brown is a Web page that deals with every issue of any type of bike you are looking for info on.

Info for the Peugeot Mixte UE 18 bottom bracket (spindle size and all) can be found on this page in the section on bottom brackets.

... a Japanese spindle made for an Italian size (70 mm) bottom bracket will usually fit! In the J.I.S. marking system, these are the spindles that are marked with a "5" code. Spindles for 68 mm bbs have codes beginning with 3. This trick often makes it possible to upgrade an older bike from cottered to cotterless cranks ...

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    Sp the OP does not have to trawl through the SB's site, can you at least provide a link or name of the particular page? Or better, paste the info from the page you are referencing? – Argenti Apparatus Sep 30 '17 at 21:13
  • This is the page, I've looked up several different issues and have gotten the most specific info here. sheldonbrown.com/velos.html – Kenny Browne Oct 1 '17 at 5:42
  • I edited your answer to include the link to the SB page and quoted the paragraph I believe you are talking about. Friendly FYI, you can edit your answers to if you want to improve or update them with new info. Have a look at the tour to see how this works. – Argenti Apparatus Oct 1 '17 at 12:05
  • Thank you for taking the time to go over it, I've checked out that site several times for various issues and they have pretty good info on most bike and almost anything to do with them. Although sending some one to a website may not be an answer, it was what I had available to me and I do believe he is looking for information so give me a break David Richard. – Kenny Browne Oct 1 '17 at 21:46
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As far as I can remember, when looking for a crankset, for each chainring a number in millimetres is given by what the chainline will be affected. E.g. - for Sturmey-Archer FCT single chainring series it is +4 mm. It means that the sprocket is 4 mm to the right (outside) past the end of the spindle. Knowing this you need to find the correct spindle to get the chainline to the desired value.

I'll share my somewhat ghetto method of converting a Motobecane (thus French) frame to fixed-gear where I've put a cotterless spindle.

Since the drive-side cup was seized and French threads are not available for cups of cartridge bottom bracket I've came up with an ingenious idea to keep the existing cups.

I've managed to find a spindle (Miche Team 68x107 with BSA cups) where the outside diameter of the cartridge bearings almost fit the inside of the cups (tiny bit of filing the bearings helped).

To compensate for the wider bottom bracket of Motobecane frame and to keep the chainline more or less correct I've put a (ground-to-size) washer on the drive side.

This setup got me going for more than a thousand kilometres already. If I was to make a similar conversion again, the only thing I would change is to take pictures to clearly show what and how was done.

I hope it helps.

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