Bottom bracket spacing/ front derailleur
10-09-15, 09:23 AM
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Bottom bracket spacing/ front derailleur
I'm having an issue with a build I am doing. This is the first time I have built a bike and I have it all together, but I am having issues with tech front derailleur. I can not get it to adjust out far enough to shift into the large chainring. I have a 3x9 shimano setup. I am wondering if I need to move the spacers on the bottom bracket from one side to the other to allow the derailleur to reach all the way out to the large chainring. The derailleur I bought is a deore and the crank is a xtr. Any help would be appreciated.
10-09-15, 09:30 AM
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What model crankset, bottom bracket and derailleur are you using? Can you move the derailleur far enough by hand?
10-09-15, 09:33 AM
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Measure very carefully from the center line of your frame (probably the middle of your seat tube will work best) to the center of the middle ring and let us know what that number is.
It should be around 47.5mm, but if it is not, then that will help know how to proceed.
The exact model of your crank and FD will help. It will stamped on somewhere FC-XXXX and FD-XXXX.
It should be around 47.5mm, but if it is not, then that will help know how to proceed.
The exact model of your crank and FD will help. It will stamped on somewhere FC-XXXX and FD-XXXX.
10-09-15, 10:09 AM
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You've tried adjusting the limit screws?
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10-09-15, 10:49 AM
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I will look at the part numbers tonight and measure the distance to the middle ring. Pulling the derailleur out by hand and setting the limit screws all the way out, still does not get me out far enough.
10-09-15, 11:23 AM
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Your dilemma is a prime example of what happens when you "put together" a bike without understanding the relationship between interacting parts, as well as between parts and the frame. The problem is not likely the front derailleur but rather the frame/BB setup. The first step you need to do is determine the rear chainline. The next step is to match the front chainline as close as possible to the rear, taking into account which gears you will tend to favor (lower or higher). Make sure that the BB you use is matched to the crank arms. Once you have done that the likelihood is that the front derailleur will work.
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There's no such thing as a routine repair.
Don't tell me what "should" be - either it is, it isn't, or do something about it.
If you think I'm being blunt take it as a compliment - if I thought you were too weak to handle the truth or a strong opinion I would not bother.
Please respect others by taking the time to post clearly so we can answer quickly. All lowercase and multiple typos makes for a hard read. Thanks!
10-10-15, 01:50 PM
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Ok, the parts list for what I have is as follows,
shimano sm-bb90 bottom bracket
fc-m970 crank
fd-m590-10 front derailleur
I also measured the spacing and it at about 53.75 mm. I am guessing that is where my problem is. Right now I have two spacers on the crank side, is switching the spacers to the other side the appropriate solution to change the spacing? Thanks for all the input!
shimano sm-bb90 bottom bracket
fc-m970 crank
fd-m590-10 front derailleur
I also measured the spacing and it at about 53.75 mm. I am guessing that is where my problem is. Right now I have two spacers on the crank side, is switching the spacers to the other side the appropriate solution to change the spacing? Thanks for all the input!
10-10-15, 01:52 PM
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Originally Posted by cny-bikeman
Your dilemma is a prime example of what happens when you "put together" a bike without understanding the relationship between interacting parts, as well as between parts and the frame. The problem is not likely the front derailleur but rather the frame/BB setup. The first step you need to do is determine the rear chainline. The next step is to match the front chainline as close as possible to the rear, taking into account which gears you will tend to favor (lower or higher). Make sure that the BB you use is matched to the crank arms. Once you have done that the likelihood is that the front derailleur will work.
10-10-15, 02:04 PM
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The word "chainline" in my post is a link to Sheldon's explanation, including how chainline is measured. No sense in redoing it here. Another page discusses chainline specific to multi-speed bikes.
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There's no such thing as a routine repair.
Don't tell me what "should" be - either it is, it isn't, or do something about it.
If you think I'm being blunt take it as a compliment - if I thought you were too weak to handle the truth or a strong opinion I would not bother.
Please respect others by taking the time to post clearly so we can answer quickly. All lowercase and multiple typos makes for a hard read. Thanks!
There's no such thing as a routine repair.
Don't tell me what "should" be - either it is, it isn't, or do something about it.
If you think I'm being blunt take it as a compliment - if I thought you were too weak to handle the truth or a strong opinion I would not bother.
Please respect others by taking the time to post clearly so we can answer quickly. All lowercase and multiple typos makes for a hard read. Thanks!
10-10-15, 02:05 PM
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Originally Posted by Mjoshualong
Right now I have two spacers on the crank side, is switching the spacers to the other side the appropriate solution to change the spacing?
__________________
There's no such thing as a routine repair.
Don't tell me what "should" be - either it is, it isn't, or do something about it.
If you think I'm being blunt take it as a compliment - if I thought you were too weak to handle the truth or a strong opinion I would not bother.
Please respect others by taking the time to post clearly so we can answer quickly. All lowercase and multiple typos makes for a hard read. Thanks!
There's no such thing as a routine repair.
Don't tell me what "should" be - either it is, it isn't, or do something about it.
If you think I'm being blunt take it as a compliment - if I thought you were too weak to handle the truth or a strong opinion I would not bother.
Please respect others by taking the time to post clearly so we can answer quickly. All lowercase and multiple typos makes for a hard read. Thanks!
