HI all:

I am looking for advice while I rebuild a 1980(?) Motobecane "Le Champion" frame, specifically how to size the bottom bracket I need to get.
I know the bb is french threaded, so i can either get a phil wood/ ebay loose cup/bearing type, or a velo orange sealed unit. My questions are:
How do I know what spindle length I need? I am wanting to get a "correct" campy crankset, should I get the crank first and then measure something on it to size? Is the spindle size well known for these bikes?
Is there anything I am missing to get myself a correctly fitting bb?

Thanks all

Hank

Welcome!
Get the crank first then you can source the manufacturers recommended spindle length by the model of the cranks online.

https://velobase.com/default.aspx

Have you thought about your gear ratios? A campy means you are stuck with a small of 42 (a 41 was made but not exactly easy to find). If you go with a stronglight 93, you can (a) fairly easily track down a stronglight French threaded BB with the correct axle and (b) track down a 37 tooth inner chainring: https://www.redclovercomponents.com/..._37_Teeth.html. Or you could run a Stronglight 99 and easily run a compact set up (say a 50/34). I have no idea what kind of gearing you need but you may want to consider a Stronglight crank even if going all campy on this bike.

Also Campy crank is ISO and the modern French threaded BBs you will find are JIS. I dunno how much that matters in real life but it is something you will want to consider:

https://www.sheldonbrown.com/bbtaper.html

If you're willing to pay the money, Phil Wood will have what you need:

https://philwood.com/collections/squ...ottom-brackets

Since posting, i have found this info:


which would seem to indicate the bike came with a 112 mm stem

As for choosing a different crank as bikemig suggests...why would that improve ease of finding a correct bb?
Thanks!

Hank? Are you certain the BB is French threaded?

I had the same question.

Moto bb shell should at least be Swiss by 1980. Not sure the year of the frameset, but looks around '81. Here's the '81 Catalog catalog page.



Check out the catalogs hosted by our bulgie , here:

https://bulgier.net/pics/bike/Catalogs/Motobecane/

Regardless of year, the Le Champion always seemed to have mostly Record/Nuovo Record group. If a Gran Sport crank was used, it was the 5-arm Nuovo Gran Sport, not the 3-arm one, which would look weird with this '80s looking paint scheme. Velobase says that 5-bolt crank takes a 120mm spindle.

The suggestion was mainly about gearing. If you stick with a 144 bcd crank, your small chainring will be a 42. If you run a Stronglight 93, you can go as small as 37 and even smaller with a Stronglight 99. That may not matter to you but it's worth thinking about the kind of gearing you need. Personally, I think about the kind of gearing I need to climb a 10% or better grade which is why I like Stronglight cranks on a vintage European parts build. I'm running a Stronglight 99 with 47/32 rings on my 1977 Trek TX 900 for that reason. YMMV.

Going with a Stronglight might help with the BB. A French threaded Stronglight BB won't be that hard to find but Swiss will be harder. Also I *think* Stronglight is JIS and it will be easier to find a JIS French or Swiss modern BB than an ISO one assuming that difference matters. Maybe it doesn't matter much but it's something you need to think about.

https://www.sheldonbrown.com/bbtaper.html

https://www.renehersecycles.com/bottom-brackets-demystified/

Bottom line is that you may be totally happy with the gear ratios you get with a campy NR crank and/or really like the idea of restoring the bike to original spec. But gearing is worth thinking about before you build the bike up.

Whew! I would have to say that sizing spindle lengths for square-taper cranksets is one of the darkest of arts, respecting the outfitting of vintage bikes. The original fit, "standard"used and tolerances of manufacture combined with the low angle of taper (2 degrees), how "thick" the bearing cups are (Campagnolo made both "thick" and "thin" at different times) crankarm socket wear considerations for previously used cranks, whether any lubricant is used, and how tightly the cranks are torqued, make it an extremely "trial and error" proposition. Oh, and did I mention that some spindles are slightly asymmetrical, the crank end being a bit longer than the non-drive end (see Campagnolo cuts above)? Then there's the conundrum of "Campagnolo" taper. Campy tapers were actually somewhat stouter (or larger in dimensions) pre-1993 or so, when Phil Wood did not really manufacture a "Campy" taper, but told folks to use the JIS taper -- after that, Campy slimmed their taper a bit to match ISO taper. Lots of fun there. Phil Wood themselves sort of acknowledge the problematic nature of all this on their square taper page:
"Phil Wood & Co. does not assist in determining which bottom bracket is correct for any particular application. We recommend taking the frame and crank to a local bicycle shop as they should be able to help in selecting the correct bottom bracket that is needed."
Amen.
A useful point of departure would be to get a matching crank and spindle that were originally intended to be used together for a double crankset (and the correct size of bearing balls). Presumably that would give a reasonable chainline (where the midpoint between faces of the two chainrings is located about 43.5 mm* from frame (and presumably the bottom bracket shell) centerline. Failing that, I've found that Campagnolo and Sugino tapers and spindles are fairly interchangeable. Stronglight and T.A. cranks seem to work well enough with JIS taper spindles too. Sticking with JIS for (now only "vintage" where Shimano is concerned) square taper bottom brackets and cranks might be easier, actually, than getting into the weeds with the more C&V European stuff might make things easier, in the long run.
But if you're mixing and matching, trying to determine in advance "what length spindle do I need" is just a crapshoot until you actually try it. I would suggest getting access to Sutherland's Manual 6th edition (apparently available in PDF form online), which has a very good section on bottom brackets dimensioning and compatibility between brands.
What you're looking for are two things basically: achieving a decent chainline, and getting the fit of spindle taper and crank socket sufficiently correct so that the end of the spindle is neither recessed too far into the socket (inadequate support between spindle taper and crank) or projecting out of the socket (can't tighten the crank arm sufficiently). Having the spindle end (when torqued down!) about 2–3 mm from the end of the socket is ideal.
At the very least, make a decision about exactly what cranks you actually want to use, and then people here can be more helpful regarding what has worked for them in that situation.
*43.5 mm is not a hard-and-fast criterion, of course, just the general neighborhood of where a double crank wants to find itself. A prime consideration is whether there's interference (free-spinning, or under pedaling/chain load) between the inner ring and the right chain stay; which also has to do with how large in diameter the inner ring is.

My approach to this, in general, is to have more bottom brackets than I need so I can try several to find one that fits. That's my short version of what Charles wrote above.

Hi everyone,
wow, what a plethora of info! Thanks so much for the replies. I will think it over and have updates in the coming week.
As for my double posting of the campy article...I am not the most tech savvy, and I thought the reply didn't go through so I re sent it...oops!
Thanks,

Hank

the Campagnolo three arm GS cranks originally came in steel, later aluminum.
by the aluminum arms, the spindle will probably be 115, offset about 3 mm more to the drive side. both the 112.5/113 will also be offset to the drive side.

the taper length and overall can get tricky.

the thick cup - thin cup cha cha cha is for most confounding. the thick cups were for the Nuovo Record BB assemblies to use the reverse internal bore threading to expel dirt. the lesser grade units continued with the "thin" cups....

overall a " hot mess" as it has been described.

I plan on using a campy crankset such as the one here:


which is a 52/42 tooth campy super record crankset, 170mm arm length with a square taper. I did not realize that there were a 3 and a 5 spoke super record crankset, i want the correct 5-spoke one however.

Based off this, looking at velo base I have identified it as this part:

unfortunately the threading is defined in English or Italian only...oh boy.

Here is the velo page with what I assume is a matching campy record bb (part no 1046, as in the article I posted earlier):


This indicates only two lengths, but the article has many more...still looking like any 68mm long bottom bracket wants a 112mm spindle for road use. Wondering if the database is incomplete, or if the track part is different.
I do have a campy record crankset on the way, then I will get to measuring to really gain confidence.

Although then that begs the question...what dimension of a Crankset determines a good spindle length?

Thanks,

Hank

The earlier reference to 3 & 5 bolt patterns was for Gran Sport, not SR.


That's just letting you know the two different spindle lengths for 70mm bb shells (Italian) and 68mm (everything else).

Does that mean for a specific crankset, the needed spindle length is decided based on bb length?

your in transit Record crank set will want a spindle to match the crank date- 1977 <7>
and beyond will be in post CPSC territory, 115 mm.
the earlier was 112mm. Identifiable by the shape around the spindle port.
1976 could be either...
the way of things.

is this the marking you're talking about:

hard to read, but it says: " 170 STRADA <4>"...does that indicate 1974?

Excellent, thanks for the help on that one.

Now...I have not forgotten that several of yall are doubtful that I have a French threaded frame, instead saying it's Swiss.
I see markings 35x1 on the bb housing, but researching bb length indicates both swiss and french threads are this size/marked this way. Is there another way to tell, short of having a bb to try to thread in?

Thank you, I'll check the frame when I get home.

Funny to me that the French decided to go nonstandard for thread direction of all things...I must get myself some of whatever they were smoking in France at the time

Both French (35 mm) and Italian (36 mm) have drive-side (actually, both sides) right-hand thread. English (1.370 inch or 34.78 mm) and Swiss (35 mm) have drive-side left-hand threaded. It wasn't a matter of smoking anything. The French and Italians each had a substantial bicycle industry, and had developed their own standards to support it, evidently deciding that the complexity of having cup and BB threading different on each side wasn't worth it, when the precessional loosening problem could be solved by tightening the fixed cup really tight.

Sometimes the only reliable way to figure out the French / Swiss mystery is to pull the fixed cup. Total PITA when the cup could have simply been stamped 35x1 L or R (or D and G for the French).

IIRC old Stronglight and TA used a system of ring markings on the fixed cup, or knurling the adjustable cup lockring (of all things) to indicate BB threading.
Good old Sutherlands Guide used to be the source for that info.

Welcome to the bizarre world of bike threading. Next up is Headsets and Freewheels.