Campagnolo Bottom Bracket Spindle Secret Decoder Ring?
In hunting for vintage parts, the bottom bracket is the area I always find most mystifying. As I'm currently focused on building up a 1970 Atala which will have a period-correct Campagnolo crank, and most of my other steeds are Campy-equipped, I'm going to restrict my observations and questions to the classic square taper Campagnolo bottom bracket. I've attached a scan of pg 3-10 from Sutherland's 3rd edition, which identifies the various (common? only?) Campy spindles available at the time of its publication (1980).
I think there are four main variables at play here:- Bottom bracket shell width. It is encoded in a straightforward manner as the initial number (most commonly 68 or 70, though narrower and wider shells existed, as indicated in the table).
- Rear triangle spacing. Rear spacing would seem to be indicated by the 110 or 120 suffix. 110mm rear spacing used to be common on the track (and judging by my reading of eBay auctions for NJS parts, may still be in use in at least some Keirin setups).
- Number of chainrings. The distinction between single and double chainrings appears to be encoded a bit more indirectly as "P" (pista) or "SS" (servicio strada?), respectively. Triples are indicated by "SS" and "X3".
- CPSC edicts. There's an extended footnote underneath the table describing the CPSC-related machinations. Basically, I think the CPSC change moved the crank arm out about 1.5mm relative to the chainrings to clear the newly added lip on the front derailleur. I've seen some of these axles. The description there, while a bit long, seems straightforward. Adding some width on the right suggests the need to do the same on the left, for symmetry's sake. Why they didn't add the same on both sides seems a bit odd.
Now for some questions.- What does the "Z" suffix mean? I see no rhyme nor reason for its presence or absence in the markings in the attached table, other than always or never being present in a certain section of the table.
- Why are there no "126" markings? Clearly, by 1980, normal (non-Ultra) six-speed freewheels had long been available. A recent discussion on Classic Rendezvous indicated that they were available (though not widely used) starting in the mid-1960s. The move from five to six speeds (and widening of the rear triangle to 126mm) would have had nearly a significant effect on chainline as the addition of a third chainring. Did people just use "X3" spindles on six-speed setups to account for slightly bigger chainline?
- What about English v. French (see the table)? Aside from cup threading, shouldn't they have been identical? Why are the center width and axle end factors so frequently (slightly) different between them? (I think these factors are based on measurements the Sutherland folks made to help mechanics find replacement parts which were more-or-less interchangeable, but I'd be happy to learn of a better explanation.)
- A mystery to me is what "SSS" means, or why there would have been a road double setup with a 74mm bottom bracket shell (both in the middle section of the table). Maybe for tandems?
- Finally, moving a bit closer to the present time than my old Sutherlands, the "120" marking seems to have disappeared altogether. I have a spindle in my box marked "68-SSB". Searching Google and eBay it seems this was a C-Record era Chorus or Athena spindle. Had everyone gone to 126 at that point, making a spacing number completely irrelevant? If so, what does the "B" suffix mean?
