WF Holdsworth

I see old Campy record cranks for sale on ebay and the seller describes various measurements... I understand the crank lengths (e.g. 170 or 165, etc.) but the other I am not sute of. There is a measurement described as "bcd" that I assume is a reference to the distance between the mounting bolts for the chain rings. Am I correct?

cuda2k

You are correct. It's the size crank rings that mount to it. I don't know exactly how the measurement is made off the top of my head - but if the crank states the bcd - then you need only find rings of the same specification. Believe Sheldon Brown's site explains the measurement - or somewhere someone has asked here on the boards and can be found with the search.

luker

oldest 5 arm campy cranks are 151 mm bcd (bolt center diameter, I think).
nuovo record/super record are 144 mm bcd.
anything newer is 135 mm bcd.

The old stuff is getting astronomical - the 144 is simply very expensive, and the new stuff
ranges from expensive to cheap - but you must be careful, as Campy added new groups
in the past (like veloce) that do not use as nice a finish or material, but can pass for
record/chorus/athena at a glance (or an ebay picture).

There are a few other dimensions to worry about, depending on what you are building.
The crankarm length (170 mm was the practically universal length in the past so there
are a passle of these in existence today). The threading for the pedals changes depending
on nationality of distribution - French pedal threads are not English pedal threads. I dunno
if Swiss is again different or not. (Italian and English are the same.)

number6

bcd, an acronym for bolt circle diameter.
Old Record, 151 BCD min ring 44T
Later Record from 1968- essentially, 144 BCD 42T minumum, although to be perfectly correct Campagnolo did make a small number of 41T rings. Record is commonly referred as Nuovo Record, and later Super Record.

The Pista (track) sets kept the larger bolt circle for a while longer until about 1973, then went to 144 BCD

the BCD is measured in mm in all cases.

Remember as far as BB spindles go it does matter if the crankset you are looking at is pre or post CPSC (Consumer product safety commission) mods. Post CPSC will require a longer spindle to keep the chainline happy and in some cases the chainstays unmarked. Tomorrow night some images to assist.

luker

I have yet to see a 41 in 144, but I am sure that the option was discussed at the bike shop back when. Did anyone else make 41's, like Ofmega, maybe? I would like to find a source for a 41 or three...

jacksbike

I believe that Zeus, a Spanish copy of Campy, manufactured interchangeable parts for Campy. Not sure if they made a 41 T ring, most likely 42T.

WF Holdsworth

Thanks for the information... how do you measure BCD?

number6

Cycles De Oro recently had a NOS Campagnolo 41T ring for $49.99, sold quickly. TA also makes 41T rings, not cheap but technically avail. and match, kind of Super Record looking. Stronglight did as well, doubtful you will find one. The problem with the 41T ring is that with some chains such as an old Regina Extra, the side plates are big enough to have the chain hit the spider arm, the clearamces are that tight, A later Regina Record, the one with the drilled side plates and or a later Sedis is what is needed, there are probably some others that work.

Measuring BCD is not the easiest thing to do as one is measuring a virtual point, Sutherland's Reference for bicycle mechanics had a printed full scale chart in one of the later editions, 3rd or 4th? that made things much easier. With that chart one just dropped the part in place and sighted it.

WF Holdsworth

Funny you should mention the TA chain rings. I have a set of Stronglite cranks (I don't kow what model) that have TA chain rings attached. The chain rings attach at the base of the crank arms which is something I have not seen before.

number6

Those are probably from the cyclotourist type patterns. TA still makes rings for those. Everyone eventually copied the Campagnolo bolt hole circle of 144, just as Campagnolo changed theirs...

Another possible way to measure the BCD is to measure between adjacent holes, not that great as the nmbers are not pretty, 101.82mm (4.008")for 144mm bcd, need a venier caliper for those.

greybeard87

When in doubt, refer to Sheldon Brown:

https://www.sheldonbrown.com/gloss_bo-z.html

OLDYELLR

As already noted, Shedldon Brown shows a method for measuring BCD. Also, there are a couple of tricks used for measuring 5-bolt circle diameters directly on car wheels which give a close approximation.




or