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Thread about converting French cottered crank to non-cottered

Old 08-05-20, 06:49 PM
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Thread about converting French cottered crank to non-cottered

Starting a new thread about this for the sake of searchability.

Back in a day when my parts pile was much larger, I didn't bother writing stuff down. I'd just dig thru my bucket of spindles until I found one with same width between races and within 1mm-2mm left and right measures. I don't have that luxury anymore. Not only is my parts bin dwindling from sharing with donating to co-op, friends, sharing with fellow BF'ers, and downsizing, but vintage parts are becoming more and more scarce.

I needed to pay attention this time so I could stock up on some extras. Knowledge is power so I'm leaving some notes here with information about how to make this conversion.

First, French cottered cups - maybe all French cups - are notoriously thin-walled to the point installing a regular (non-French) 68mm spindle won't work - the width between races is ~52mm so skinny your lock ring won't get enough bite with the expected bearing ball size. The solution to this issue is stupid: Use an Italian 70mm spindle, which has ~55mm between races, which happens to match the width between races on French cottered spindles.

How do you know which spindle will have the approximate width? If you have a bucket of extra spindles like me and you want to avoid digging, how can you easily tell which one will work? Well, as you see in this thread, you can punch around in the dark with some trial-and-error and find the right dimensions with the wrong tape. Or, as you read in that same thread right here, you can stop and learn what the stamping on spindles means, measure the cottered spindle, and use the codes stamped into the spindle to figure out what works.

There's not a ton of info on BF on this topic, the topic of spindle stampings. Or if there is, I couldn't find it. On my specific application, I was converting a Peugeot Grand Sport from cottered to non-cottered for a friend. I noticed one spindle I had marked "5K" was dimensionally correct but the taper was completely off, maybe for older BMX? I wanted to find one similar, but until I referenced Sutherland's Handbook, I didn't understand what the stampings mean, so I didn't even know where to start.

Short story long: Not every spindle has numbers and letters stamped into them. For those which do, here's the decoder ring:
Basically, if the spindle follows the standard above, it would have sometimes a letter, always a number, followed by either one or two letters.

The number is probably the most important thing, it defines the width between races (measurement "B" below), which dictates what width of BB shell it's intended, where 2 = 65mm shell (track), 3 = 68mm shell (French/ISO/Swiss), 5 = 70mm shell (Italian), and 7 = 73mm shell (Older UK/Raleigh). So the number helps you find the correct width between your races, the letter(s) to follow that number explain how far the left and right side stick out, which is critical to ensuring your crank arms will sit far enough out not to whack your chainstays.
To get more in-depth, think about those numbers. If your BB shell is wider, it means the ridges/races on your spindle need to be farther apart. If not, by the time you crank your cups down onto the spindle, if the spindle races are too close together, the cups will be inside the BB shell totally, making it impossible to use the lock ring. Going back to the 2/3/5/7 numbers stamped on the spindle above, those numbers tell us the exact distance between races, so we get a great idea where it will fit, even if it wasn't intended to go there.

2 = ~50mm between race edges
3 = ~52mm between race edges
5 = ~55mm between race edges
7 = ~57mm between race edges

This point was biting me in the ass with the conversion I was working. Not having a huge supply, I couldn't do the usual plugging to see if something fit. I mentioned earlier French cup walls are a bit skinnier than most. It just so happens, this is intentional, and if you measure a cottered French spindle, you'll notice it's roughly 55mm between races. But wait - that's the same as a "5", which is Italian - fitting a 70mm shell. So basically, with this French situation, we have a 68mm shell using a spindle race width for Italian.

At this point it was clear: I needed a cotterless spindle with a stamping of "5" because those they're ~55mm between the races, i.e. a 70mm spindle, or a 68 BB using cups which are ~1mm thinner (70 - 1 -1 = 68).

After a good trade with smontanaro I acquired a small stimulus of extra spindles. Some 68 (3 stamp), a 70 (5 stamp) and a 73 (7 stamp). With luck, it just so happens the one 70mm spindle, stamped 5SP was virtually identical in measure with Peugeot's cottered spindle. ~55mm between races, and the 5SP spindle ends stopped near the middle of the cotter cutouts on the factory Peugeot spindle, putting my crank arms in nearly the right place after everything is tightened down.

tl;dr here: If you're trying to convert a French 68mm BB with stock French cups to non-cottered, you'll need an Italian spindle if you want to use the stock cups. If you're hunting in your own bin or a bin at the co-op, you'll want to hunt spindles stamped with "5". I saw a confirmation "5N" spindles will work, and I have now tested 5SP and D-5SP spindles, both also work. Chainline is good.

Your mileage may vary. But generally speaking, this conversion isn't bad if you know what ot look for and have access to some parts. While 5N spindles aren't readily available online, I've noticed there are still a couple sources with 5SP / D-5SP spindles available and they'll work also.

Here's what I'm looking at on a late 70s Pegeut Grand Sport, roughly the same level as a OU-8 / UE-8 in the heirarchy, while using the 5SP spindle and a JIS crank, an SR Apex swaged crank. I could probably use 1-2 mm inboard on the drive side arm, or 1mm out on the non-drive side, but after slapping on a chain and dialing things in, I'm not showing any ill effects. Chainline is OK, shifts are smooth.

Hopefully this info helps someone in the future. If I would've learned this 5 years ago, 10 years ago, 20 years ago, I couldn't finished a few builds and a few customer services a hell of a lot faster. At least I learned, hopefully if you read this far, you did too.
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Last edited by francophile; 08-06-20 at 11:15 AM.
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Old 08-05-20, 06:52 PM
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Oh, and here's another fun point.

On a whim, while running through this one, I pulled a Stronglight 118mm with mild pitting out of a small parts bin. Stronglight used very generic stampings. I need to dig to find a few more to see if this is consistent - I don't know if this was intended for 73mm shell or what, but this was the 118mm Stronglight spindle sitting next to a French cottered spindle. The French spindle is ~55mm between races. I guess the Stronglight is around 57mm between races on what I'm seeing, perfect for an old Raleigh with 73mm BB.

Could it be any more confusing?

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Old 08-05-20, 07:14 PM
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.
...this is why those Velo Orange French threaded sealed unit cartridges are such a blessing.
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Old 08-05-20, 07:25 PM
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Originally Posted by 3alarmer View Post
.
...this is why those Velo Orange French threaded sealed unit cartridges are such a blessing.
I hear you. If they'll ever get to a more marketable and user-friendly price point on their BBs, their product would make a lot more sense. I had two choices here, as many others finding themselves in this position do:

1) Spend $50 on a sealed unit from VO on a bike that cost $10.
2) Pay $7 to ship a trade to a BF'er to get 10+ spindles enabling me to do 10+ conversions like this.

I opted for the latter.

The fix above will also work for Swiss-thread situations where a sealed BB may not be feasible or possible.
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Old 08-05-20, 08:00 PM
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$16 for a french threaded bottom bracket set from Amazon:

https://www.amazon.com/Action-Bottom...6679125&sr=8-8

Honestly I didn't think about any of this stuff when I converted my UE 8 to cotterless. I just grabbed a likely looking english spindle and it worked. I was able to get a good adjustment and the ball bearings hit more or less on the right spot on the spindle.
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Old 08-05-20, 08:05 PM
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I would think choice of crankset will also be a major factor, particularly wrt spindle taper/fit. I’m working on a project in which I can’t swap out the BB spindle, and it’s remarkable how many mm differences there is with how much clearance different cranksets have to the chain stay, even when they’re the same manufacturer (e.g., Stronglight). Of course, all of those cranks are used, so who knows how much the openings have deformed with repeated use.
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Old 08-05-20, 08:28 PM
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Originally Posted by bikemig View Post
$16 for a french threaded bottom bracket set from Amazon:

https://www.amazon.com/Action-Bottom...6679125&sr=8-8

Honestly I didn't think about any of this stuff when I converted my UE 8 to cotterless. I just grabbed a likely looking english spindle and it worked. I was able to get a good adjustment and the ball bearings hit more or less on the right spot on the spindle.
One thing about the Action cups: They're thicker. If someone were to buy those, they could probably easily get away with a standard 68mm ("3" stamped) spindle.

Not saying that's what you did on yours, but that's definitely an option available.

In this specific bike, I probably ran through 6 different 68mm spindles with no joy. Couldn't get a locking after. If you were using stock cups and managed that, you won the lottery. I've done this swap in the past and it was never that easy for me.
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Old 08-05-20, 08:31 PM
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Originally Posted by nlerner View Post
Iím working on a project in which I canít swap out the BB spindle, and itís remarkable how many mm differences there is with how much clearance different cranksets have to the chain stay, even when theyíre the same manufacturer (e.g., Stronglight). Of course, all of those cranks are used, so who knows how much the openings have deformed with repeated use.
Curious to hear more details on your project.

I've got a few cranks on my workspace right now. I'm planning on throwing a few on. This bike won't end up with an Apex, I'm looking at a Maxy to pair the crank with the level of bike.
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Old 08-06-20, 05:39 AM
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francophile Great info! BB's are still confusing. My focus has been Italian and more specifically Campagnolo. There markings are consistent but what is marked is not.
P1030105 , on Flickr

Did your Stronglight have markings as you described? Here is mine that came with a 93 crank on a Le Champion frame.
Stronglight BB Inside Cup , on Flickr
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Old 08-06-20, 11:11 AM
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Originally Posted by SJX426 View Post
francophile Great info! BB's are still confusing. My focus has been Italian and more specifically Campagnolo. There markings are consistent but what is marked is not.

Did your Stronglight have markings as you described? Here is mine that came with a 93 crank on a Le Champion frame.
Stronglight doesn't follow the number/letter stamping. With exception of mid-80s onward, I think I've only ever seen exactly what you show there, which is the width, but no info on spacing.

Campy does stamp, but not the pattern above. Your photo of the Campy 70mm spindles illustrates an issue even worse than I'm seeing with Stronglight. At least with Stronglight they don't post the shell size. Clearly one of those Campy spindles is wiiiiiiiiide. Unless the angle of the picture is strange, it looks like that one on the bottom must be 57-58cm on the B measurement. No way that's fitting in an Italian shell?

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Old 08-06-20, 01:02 PM
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francophile so this is the fun part. Campy also has thin cups. That one spindle requires thin cups on both sides. I have a non drive side thin cup but not the DS cup. It was the length I needed but didn't come with the cups! I am open to buying a DS thin cup at this point just to complete the BB assembly. I ended up buying a complete BB to work.

More detail in these two links.
Campagnolo Crankset model vs spindle length (Square Taper Only)
Campagnolo square taper 70 ss consistancy?

BTW: The Stronglight BB shown is from a 1972 Motobecane Le Champion. Have the 93 Crank to go with it. I have since learned, through the knowledge gained in the links, not to separate the two if possible.

Lack of knowledge of what you are selling often includes lack of enough information. The buyer may be equally ignorant and buy something that won't fit, i.e. the bottom spindle.
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Old 08-07-20, 04:08 AM
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francophile Now I know why you were so happy to get that box o' spindles! Good thing I never put them in the scrap metal pile. They were sitting in my parts bin (completely unused) for probably four or five years.
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Old 08-07-20, 05:00 AM
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Thanks for this good work, francophile. Much appreciated here.
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Old 08-07-20, 08:49 AM
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Originally Posted by SJX426 View Post
francophile so this is the fun part. Campy also has thin cups. That one spindle requires thin cups on both sides. I have a non drive side thin cup but not the DS cup. It was the length I needed but didn't come with the cups! I am open to buying a DS thin cup at this point just to complete the BB assembly. I ended up buying a complete BB to work.
You know, I completely forgot about that. I remember running into this issue with a pair of rifled cups and Campy spindle not necessarily intended to be used with it - pretty sure the spindle was for thin cups and the rifled cups were thick.

Too bad nobody has created a thread to show how to measure cup thickness, what cups had what thickness variation and how to ID them, but also included some reference "B" measurements (above) on spindles so you knew which spindle went with which cup thickness (i.e. if "B" measurement is XXcm, use ITAL cup with YY thickness in ZZ bb shell width). A matrix like that which spanned multiple brands would be hugely useful, would make it easier to mix-and-match and would also be a huge sanity check resource for folks! Prime sticky-thread content!

Originally Posted by smontanaro View Post
francophile Now I know why you were so happy to get that box o' spindles! Good thing I never put them in the scrap metal pile. They were sitting in my parts bin (completely unused) for probably four or five years.
That pile of spindles solved two major issues I had for three projects now. Stuff I need to get out the door so I can move a couple more bikes from the temporary warehouse / shop space I'm sharing. Pandemic is costing me half my workspace due to kids schooling from home through October and possibly beyond. Had to relocate a lot of stuff so I could setup desks, power, network etc. so I'm working in chunks and pretty soon I'll only be able to wrench for an hour or two in the evening at home, else I'm carrying stuff over to the shop space.

Life is crazy right now! Huge changes. It'll be a good jolt in the long run to help reshape how we're organized and operating, but I was really, really comfortable with the way things were. If nothing else, the pandemic has forced me to optimize my clutter, and purge a LOT of stuff I would never use, and it's netted me some $$ n the process, which is nice, I'm probably going to need it come October if mass layoffs happen nationally as expected.
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