FSA Arm compatability
07-08-17, 07:27 AM
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FSA Arm compatability
Hi all
The FSA gossamer crankset left hand side (non-drive) arm on my bike is hosed (the retaining bolt was falling out, and I rode it long enough with the arm wobbly to damage it; even though I not have loctit-ed it into place, the arm has become wobbly again). The BB is mega-exo. I can buy a replacement lhs arm for FSA energy BB386, but I can't seem to find replacement arms for MegaExo/BB30. Best I can tell from [1] the only difference on the LHS arm between the two is curvature. So questions.
(a) am I correct, that the arm will fit, and if so will the change in curvature be noticeable?
(b) the alternative seems to be a new crankset. I would want to go to a 105 if so; would I need to change the bottom bracket? I read somewhere that shimano is compatible with non-carbon FSA cranksets.
Thanks,
Mike
[1] <www.bikerumor.com/2011/12/22/fsa-bb30-vs-bb386evo-a-visual-comparison-weights/>
The FSA gossamer crankset left hand side (non-drive) arm on my bike is hosed (the retaining bolt was falling out, and I rode it long enough with the arm wobbly to damage it; even though I not have loctit-ed it into place, the arm has become wobbly again). The BB is mega-exo. I can buy a replacement lhs arm for FSA energy BB386, but I can't seem to find replacement arms for MegaExo/BB30. Best I can tell from [1] the only difference on the LHS arm between the two is curvature. So questions.
(a) am I correct, that the arm will fit, and if so will the change in curvature be noticeable?
(b) the alternative seems to be a new crankset. I would want to go to a 105 if so; would I need to change the bottom bracket? I read somewhere that shimano is compatible with non-carbon FSA cranksets.
Thanks,
Mike
[1] <www.bikerumor.com/2011/12/22/fsa-bb30-vs-bb386evo-a-visual-comparison-weights/>
07-08-17, 09:04 AM
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I'm pretty sure that a 105 crank will fit in the Mega-Exo BB, but it's a MUCH tighter fit than if you used a Shimano BB. You will likely require a rubber mallet to hammer it in.
The good news is that it's very easy to unscrew a Mega-Exo BB and just screw in the $15-20 Shimano brand BB and not have to deal with the pounding at all if you're wary of having it be difficult to remove down the road. That's the route I would go. I recently removed a square bracket-cartridge type BB and replaced it with the stock current-gen Tiagra BB that came with the groupset, and it was trivial to install - literally just screw it in being careful not to cross-thread it. I'll note that you probably will need the correct BB tool to screw in the Shimano BB, but the tool is also <$20.
The good news is that it's very easy to unscrew a Mega-Exo BB and just screw in the $15-20 Shimano brand BB and not have to deal with the pounding at all if you're wary of having it be difficult to remove down the road. That's the route I would go. I recently removed a square bracket-cartridge type BB and replaced it with the stock current-gen Tiagra BB that came with the groupset, and it was trivial to install - literally just screw it in being careful not to cross-thread it. I'll note that you probably will need the correct BB tool to screw in the Shimano BB, but the tool is also <$20.
07-08-17, 05:19 PM
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No, a BB30 or BB386 non-drive side crank arm won't fit. They're designed to mate with a 30 mm spindle and a MegaExo spindle is 24 mm.
If you switch to a Shimano crankset, I'd install a Shimano bottom bracket as well. $15-20 is a small price to pay for a no-fuss installation.
If you switch to a Shimano crankset, I'd install a Shimano bottom bracket as well. $15-20 is a small price to pay for a no-fuss installation.
07-08-17, 05:42 PM
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I'm not sure how old your bike is, but my 2008 Cervelo P2C came stock with a FSA Gossamer crank + MegaExo BB. (This was prior to Cervelo's more recent BBright proprietary custom BB setup.)
I def could get a Tiagra 5700 (current-gen) into that MegaExo BB, but as said, I had to hammer it in. Didn't like that, so I swapped it to the Shimano BB.
I will def admit that I have no idea whether a current-gen MegaExo is incompatible, but at least with my old one from 2008, it fit.
I def could get a Tiagra 5700 (current-gen) into that MegaExo BB, but as said, I had to hammer it in. Didn't like that, so I swapped it to the Shimano BB.
I will def admit that I have no idea whether a current-gen MegaExo is incompatible, but at least with my old one from 2008, it fit.
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