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Acceptable distance between chainstay/inner ring-Chourus BB?(3 posts)

Acceptable distance between chainstay/inner ring-Chourus BB?sukotto
Jul 6, 2003 4:11 PM
I am building up a new frame and noticed that the inner chainring seems awfully close to the chainstay. This is my first time using a Chorus BB (double, I know it is narrower than most) and was wondering what the acceptable distance between the inner chainring and chainstay is? I would venture to say that this one is probably 3-4mm, but I need a set of calipers to be sure.
Not touching is acceptableKerry Irons
Jul 6, 2003 4:40 PM
What you should really be looking at is your chain line - does the center of the two chainrings line up with the center of your cassette. If your chain line is right, then any clearance issues with the chain stay are VERY secondary unless you think they'll be touching occasionally, and then you've got to ask some serious questions about your frame. If your chain line is not right, then work on that by adding one or more spacers between the right cup and the frame to get things lined up.
some numbersterry b
Jul 6, 2003 4:54 PM
well you piqued my curiousity so I went and measured some bikes. Most have 7mm clearance, but I do have one with 2mm and one with 4mm.

But it's largely academic as long as it's not rubbing. It's more a product of the length/thickness/curvature of the chainstays (assuming the BB shell is in the right place) than an indicator of a problem. As said above, if the chainline is fine it's immaterial.

Had one frame once where I actually had to grind away a couple of mm of the clearcoat to get it to work. When done, it had about 1mm of clearance.