Re: [CR]Measuring BCD - - Bolt Circle Diameter


Example: Framebuilders:Alex Singer

From: "Tom Martin" <tom@wilsonbike.com>
To: "Raoul Delmare" <Raoul.L.Delmare@worldnet.att.net>, "C.R. List" <classicrendezvous@bikelist.org>, "Bruce C." <BruceCumberland@comcast.net>
Subject: Re: [CR]Measuring BCD - - Bolt Circle Diameter
Date: Tue, 24 Feb 2004 10:25:52 -0800


And what is the BCD? don't the british and japanese prefer the term Pin Circle Diameter aka PCD?

tom martin
Oakland CA
where thy weather is faire today


----- Original Message -----
From: "Tom Martin"
To: "Raoul Delmare" ; "C.R. List"


<classicrendezvous@bikelist.org>; "Bruce C." <BruceCumberland@comcast.net> Sent: Tuesday, February 24, 2004 10:03 AM Subject: Re: [CR]Measuring BCD - - Bolt Circle Diameter


> The original question was never answered, namely how does one measure the
> bolt circle diameter of a chainring?
> -If you have the crank, it's easy:
> measure from center of chainring bolt hole to the center of the crank
> spindle taper area, then multiply by 2.
> -if you don't have the crank and only the chainring, then it's a little more
> complicated. You gotta somehow find the center of the chainring (any of you
> engineer types out there have an explanation of that?). Maybe with a compass
> and a ruler and a pencil? measure from each chainring bolt down to the other
> side, and where all the lines cross is the center? 4 arm and 6 arm cranks
> are a lot easier than the 3 and 5 arm cranks. Once you find that, just
> follow the above steps/
>
> Tom Martin
> Oakland Ca
> is cycling science in existance any longer? do they have a listserve or
> website?
>
>
> ----- Original Message -----
> From: "Raoul Delmare" <Raoul.L.Delmare@worldnet.att.net>
> To: "C.R. List" <classicrendezvous@bikelist.org>; "Bruce C."
> <BruceCumberland@comcast.net>
> Sent: Tuesday, February 24, 2004 4:12 AM
> Subject: [CR]Measuring BCD - - Bolt Circle Diameter
>
>
> > Hey Bruce ! Here's what you need to know , to see if Stronglight 99
> > chainwheel ( chainring ) will fit that crankset you just recently bought
> !
> >
> > I had seen the conversion charts before . I was HOPING somebody
> > would post them on the C. R. List ! But a conversion FACTOR is
> > something I don't recall seeing before ! THANKS !!!!!!
> >
> > In the past , looking at charts , the procedure was to measure the
> > distance , center-to-center , or edge-to-edge , between any two bolt
> > holes on your chainring ( chainwheel ) .
> >
> > BUT , you have to know which one your chart is looking for ,
> > center-to-center , or edge-to-edge .
> >
> > Then just look up that number on your little chart ! Et voila !
> > Instant Bolt Circle Diameter ( " B. C. D. " ) information about your
> > chainrings ! Personally , I'd like to see SOMEBODY post this
> > information , in a big way , SOMEWHERE ! Why not , at some public
> > location , post three ( 3 ) easy-to-use conversion charts :
> >
> > 1.) B.C.D. derived from center-to-center distance between any two
> > bolts , or bolt holes .
> >
> > 2.) B.C.D. derived from edge-to-edge distance between any two bolt
> > HOLES - but the chainring must be OFF the crank to accurately measure
> > this .
> >
> > 3.) B.C.D. derived from edge-to-edge distance between any two BOLT
> > HEADS - but the chainring must have the bolts fitted to accurately
> measure
> > this .
> >
> > This would REALLY be a big help for those "newbie" folks , who
> may
> > very likely be confused or nervous about the very idea of trying to find a
> > chainring of a different size for their bicycle ! Plus , it would be a
> > very nice convenience for even the experienced folks who have an odd
> > crankset ( or several ) ! If somebody could gather this information ,
> > it would be SO VERY convenient to see it posted somewhere like say
> > perhaps , Sheldon Brown's wonderful Harris Cyclery site !!!!!!
> >
> > http://www.sheldonbrown.com/harris/new.html
> >
> > ( Thanks Sheldon ! And those A.N.T. bicycles are very cool ! )
> >
> > And , by the way , Sheldon already has the center-to-center
> > information on his "Bicycle Glossary" page :
> >
> > http://www.sheldonbrown.com/gloss_bo-z.html#bcd
> >
> > Thanks Sheldon . And thanks Steve Maas . And thanks Brian Frank .
> > And thanks C. R. List . And I'll miss you folks for the next week or
> two
> > - traveling .
> >
> >
> > Raoul Delmare
> > Marysville Kansas U.S.A.
> > ( where we know that Dolly Madison's heroic acts saved the artwork
> from
> > the burning White House , while the U.S.A. was losing the War Of
> 812 -
> > Dolly Madison was a courageous hero , not a cup-cake ! )
> > ( and since this will be my last post for a week or two , I'll be out
> > of town , and temporarily disconnected from the list , if ya flame me ,
> I
> > won't be able to read it , sorry! :^)
> >
> >
> >
> >
> > ----- Original Message -----
> > From: "Steve Maas" <stevem@nonlintec.com>
> > To: <classicrendezvous@bikelist.org>
> > Sent: Monday, February 23, 2004 5:07 PM
> > Subject: Re: [CR]Measuring BCD -- Newbie Question
> >
> >
> > You don't need charts or anything like that. For five-hole chainrings,
> > the bolt-circle diameter is 1.701 times the center-to-center distance
> > between the holes. A hint for measuring the distance between the holes:
> > instead of trying to eyeball the centers, hold the ruler tangent to both
> > holes and measure the distance between the tangent points.
> >
> > For 144 mm BCD, the holes are 85 mm apart.
> >
> > For other numbers of holes, use the general formula,
> >
> > BCD = d / sin(360/2n)
> >
> > where d is the distance between bolt holes and n is the number of holes
> > in the chainring.
> >
> > Steve Maas
> > Long Beach, California
> >
> >
> >
> > PaulieFlt@aol.com wrote:
> >
> > > Okay gang,
> > >
> > > I have these chainrings up on eBay and it's apparent I need to know how
> to
> > > measure BCD. Can somebody explain that to me?
> > >
> > > Many thanks!
> > >
> > > Have tape measurer, will travel,
> > > Paulie Davis
> > > Los Angeles
> >
> >
> >
> >
> > ----- Original Message -----
> > From: "Brian Frank" <twobouvs@yahoo.ca>
> > To: <classicrendezvous@bikelist.org>
> > Sent: Monday, February 23, 2004 2:46 PM
> > Subject: [CR]How to measure BCD
> >
> > Paulie:
> >
> > Check out the info & link
> > http://www.hostelshoppe.com/tech_bolt_circle_diameter.php Saves me
> having
> > to scan and email you my chart. I found it by doing a google on "how to
> > measure BCD"
> >
> > Good luck with your stuff on eBay.
> >
> > Brian Frank. Toronto Canada
> > Where it is warm enough to commute but fenders and paddles are a must.