<
[email protected]> wrote:
> >You need to establish the BCD (bolt circle diameter) of the rings, as
Ian Blake wrote:
> BCD is Bolt Circle Dimension (or Distance) it is not a diameter.
>
> http://www.settlecycles.co.uk/BESPOKE/TA/ringsGuide.htm?pid=2299
>
> Sheldon Browns excellent glossary seems to be wrong on this matter his
> glossary seems to imply BCD=PCD which it is not.
The fact that my Bicycle Glossary disagrees with the Settle Cycles site
doesn't necessarily mean that I'm the one who is wrong.
There are three different "circle dimensions:" diameter, radius and
circumference. Calling the bolt-to-bolt distance a "circle dimension"
is highly non-standard.
Indeed, if you scroll down that page to the bottom, you'll see that the
term "bolt circle diameter" is used even on the same page!
The abbreviation "BCD" for "Bolt Circle Diameter" is very well
established in general usage, and making up a different definition for
the same initials strikes me as very ill-advised on the part of
Settle's Webmaster.
"PCD" is only used in British English, and in my opinion it is a poor
choice for two reasons:
·It is less obviously understandable than BCD.
·In the description of gears/sprockets, "Pitch Circle Diameter" has a
different, well established meaning (basically it's the circle formed
by the centres of the chain rollers, the effective working diameter of
the sprocket.)
Sheldon "http://sheldonbrown.com/glossary" Brown
+-----------------------------------------+
| Man invented language to satisfy his |
| deep need to complain. -- Lily Tomlin |
+-----------------------------------------+
Harris Cyclery, West Newton, Massachusetts
Phone 617-244-9772 FAX 617-244-1041
http://harriscyclery.com
Hard-to-find parts shipped Worldwide
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