Re: [CR]BB Length

(Example: Production Builders:Cinelli)

From: <NortonMarg@aol.com>
Date: Mon, 13 Jan 2003 10:55:46 EST
Subject: Re: [CR]BB Length
To: pgrizic@haggie.co.za, classicrendezvous@bikelist.org


In a message dated 1/13/03 2:26:11 AM Pacific Standard Time, pgrizic@haggie.co.za writes:


> Some of the bikes run very
> smoothly but some seem to object in the lower and the higher gears. As
> these
> bikes have been built up over the years with parts that I have managed to
> acquire - I think that maybe some of the BB's are not really the rights
> ones
> for the Cranks, either too long or too short. Does anyone have a chart of
> the recommended BB lengths matching with the various Campy Cranks? Or is
> there something else that I am doing wrong.
> Any suggestions will be welcome
>

Here's something you can do to check your problem, as an example, let's start assuming you have either a 5 or 7 speed freewheel: Put the bike in the middle freewheel gear and the small chainring. Have a friend or fixture support the bike. Look at it from the rear. The chain should appear to favoring the left. Now switch to the large front ring, look again and the chain should be favoring the right, by about the same amount that it was in the other direction. If this is the case, your chainline is properly centered. You can do the same thing with a 6 speed, but you have to (counting in from the out side) use the #4 rear cog with the small ring and the #3 cog with the large ring. I personally like the crankset a little closer in than "perfect" as I'm more likely to use the big ring with the second largest freewheel cog than I am the small ring and the second smallest cog.
Stevan Thomas
Alameda, CA