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  1. #1
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    Will I need a new front derailleur?

    Just bought a new frame and had to install a bigger BB (extra 5mm). Will I have to get a new front derailleur, or just need to readjust it. Thanks.

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    Senior Member sydney's Avatar
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    Quote Originally Posted by mitok
    Just bought a new frame and had to install a bigger BB (extra 5mm). Will I have to get a new front derailleur, or just need to readjust it. Thanks.
    Pretty sure bet the adjustment will work.

  3. #3
    Senior Member Retro Grouch's Avatar
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    Quote Originally Posted by mitok
    Just bought a new frame and had to install a bigger BB (extra 5mm). Will I have to get a new front derailleur, or just need to readjust it. Thanks.
    So exactly what part of your bottom bracket is 5mm bigger? It would also help if I knew what some of the components were like what kind of frame, crank, bottom bracket, and front derailleur.

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    Senior Member sydney's Avatar
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    Quote Originally Posted by Retro Grouch
    So exactly what part of your bottom bracket is 5mm bigger? It would also help if I knew what some of the components were like what kind of frame, crank, bottom bracket, and front derailleur.
    My guess is he is talking 68 vs 73mm shell width.

  5. #5
    LeMond Lives! Dusk's Avatar
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    Good guess! The questions come with little info to be sure. 9mm would be a S. double to triple jump

    Sydney you're doing a great job posting good anwsers here. It's nice to see.

    Cheers

  6. #6
    Senior Member sydney's Avatar
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    Quote Originally Posted by Dusk
    Good guess! The questions come with little info to be sure. 9mm would be a S. double to triple jump

    Sydney you're doing a great job posting good anwsers here. It's nice to see.

    Cheers
    Well, there are MTB cranks with recommended spinlde lengths with a 5mm spread depending on seattube diameter,but it doesn't effect derailer choice. Probaby the simplest answer is that since he's got it,just try it. Surprising how often that works. He may find if the seattube is bigger which is usually the case with a 73mm shell,he'll need a new derailer with a bigger clamp.

  7. #7
    Senior Member Retro Grouch's Avatar
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    Quote Originally Posted by sydney
    My guess is he is talking 68 vs 73mm shell width.
    That would be my guess to. That suggests that he's trying to transfer parts from a road bike onto a mountain bike frame. Cable routing, chainring clearance, and front derailleur clamp diameter are all possible incompatability issues that pop off of the top of my head. I just think that I'd be more likely to make an accurate guess if I had a little more information.

  8. #8
    Senior Member sydney's Avatar
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    Quote Originally Posted by Retro Grouch
    That would be my guess to. That suggests that he's trying to transfer parts from a road bike onto a mountain bike frame. Cable routing, chainring clearance, and front derailleur clamp diameter are all possible incompatability issues that pop off of the top of my head. I just think that I'd be more likely to make an accurate guess if I had a little more information.
    Could just be the difference in shell width requirements betwen MTB frames.

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    Look at this, I ask the question and then disappear leaving pple guessing what the hell I asked. Sorry about being so imprecise with my question. The bb housing is the same (73mm) but the spindle needed to be bigger because the smallest front sprocket was too close to the chain stays. The front derailleur clams on fine to the seat tube (it's a shimano LX). The changeover was from one mountain bike to the other. Thanks.

  10. #10
    Senior Member sydney's Avatar
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    Quote Originally Posted by mitok
    Look at this, I ask the question and then disappear leaving pple guessing what the hell I asked. Sorry about being so imprecise with my question. The bb housing is the same (73mm) but the spindle needed to be bigger because the smallest front sprocket was too close to the chain stays. The front derailleur clams on fine to the seat tube (it's a shimano LX). The changeover was from one mountain bike to the other. Thanks.
    Should work,assuming you got the right spindle length for the crank.Shimano doesn't make derailers with different reach. With the current splined BB it's more difficult to cob something together that won't work.More latitude for screwup with tapered spindles. My biggest problem has been with off spec combinations where the small ring was in so far the derailer could not reach it due to interference with the seattube.

  11. #11
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    Should work since the chainrings are in the same position. The longer spindle is just to compensate for the crank sitting further onto the spindle.

  12. #12
    Senior Member sydney's Avatar
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    Quote Originally Posted by AndrewP
    Should work since the chainrings are in the same position. The longer spindle is just to compensate for the crank sitting further onto the spindle.
    The chainrings cannot be in the same position if the small ring was interfeering with the chainstay,and now it isn't. Besides, it's the SAME crank.

  13. #13
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    By the way, to they sell different cages for the front derailleur this way I can just get one the sits further out

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