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Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

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Old 07-29-07, 08:01 AM   #1
notzofast
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Chain line, FSA bb and 9 speed shimano rear

I feel the need to adjust my chain line. From factory it comes setup so that I can use my tripple better on small and middle cogs. When on large cog and 3rd sproket (largest I'm willing to use because of cross chaining) chain line is horrible. So poor when I roll the bike back it upshifts in the rear, and if I roll it some more chain sometimes comes off.

Basically, I spend most of my time in large cog, thus I'd like to adjust my chain line to fit my needs, make it more efficient in my gears, or whatever. If this is easy I'd do it, if not I'd live with what I got.

My bike has a bottom bracket that is protruding out more on the cog side, and on the other side it's kind of sunken in and does not protrude. See pictures.

This gives me an idea of putting a 22 tooth tool on it and rotating it one way or the other until it protrudes less from cog side and more from the other side. Am I right here? Is this how I can adjust my chain line?

Bottom bracket I have, I'm ASSUMING, is FSA Ultimax ChroMo. Because my crank set is FSA and it's like the cheapest FSA bb I could find. It's possible that it's something other than FSA, as long as it's cheap.

For the rear I have shimano 105 or Tiagra 9 speed casette on Vuelta hub.

Please let me know if my plan for adjusting chain line via front is correct. If not then I'm doing shims in the back. I need this info to know if I should waste my money on bb tool or not.

Thanks!
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Old 07-29-07, 10:19 AM   #2
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I don't understand what you are talking about. 3rd sprocket doesn't mean anything to me. Do you mean the large chainring or the small chainring?

I don't know what a "22 tooth tool" is.

To check chainline, tie a piece if sewing thread around the front of middle chainring. Pull it back past the cassette until is it tight. Now move the string over until it just touches the back part of the middle chainring. The string should now line up with the middle cog if the chainline is correct.
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Old 07-29-07, 10:31 AM   #3
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Large.

22 tooth tool is the bottom bracket tool.


I'm asking if I can use bb tool to rotate bottom bracket either in or out (left or right) and via doing so adjust how far the cog (front gears, the tripple) is away from the frame, and thus alter my chain line?

I get this idea because bottom bracket (the shiny part in the picture) is protruding more from the side of the front gears and less from the side opposite to it, the left.
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Old 07-29-07, 11:33 AM   #4
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Small adjustments can be made by adding spacers to a BB cup, but the only direction is outward on the drive side according to the thickness of the spacer. Keep in mind that any movement outward will make your non-drive crank move closer to the chainstays. No, you can't just turn the cup out. It has to be tightened against the BB shell.
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Old 07-29-07, 01:15 PM   #5
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Large.

22 tooth tool is the bottom bracket tool.


I'm asking if I can use bb tool to rotate bottom bracket either in or out (left or right) and via doing so adjust how far the cog (front gears, the tripple) is away from the frame, and thus alter my chain line?

I get this idea because bottom bracket (the shiny part in the picture) is protruding more from the side of the front gears and less from the side opposite to it, the left.
The problem is you are cross chaining, and all bikes just don't perform well at the extremes. If you can ride on the big/big combination and it stays in gear, even when you back pedal, go ahead, it just isn't recommended. To keep it from shifting when you roll it backwards, just don't roll it backwards.

The solution is to ride on the middle CR. You will be able to have exactly (if not, very close) the same gear as the big/big combo, but it will give you much more flexibility in shifting up or down.
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Old 07-29-07, 01:28 PM   #6
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Middle is a posibility. I can achieve on the middle pretty much same speed but I have to spin more. I really like the big cog. Basically, I'm 9 speed. I don't use first two gears on big cog, so that I can avoid cross chaining. Big cog gets me going really fast on the flat. Upper 20s is not a problem. I can also go uphill just on the big.

Idea I had is to make it so that I am less cross chained in the big and middle, but more cross chained in the small. Because I don't use small that much or at all.
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