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  1. #1
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    Crank hits chainstays after new crank and bb installed

    Hi,

    A short summary for easier reading:

    Bike model: Reid Granite 2.0 (they call it a gravel bike. I use it for all purpose commuting)


    Went from a stock Claris FC2450 crank to a 105 crank.
    Both are double chain rings.

    Stock Claris Bottom bracket octalink 68mm.
    New 105 crank , new Hollowtech 105 bottom bracket 68mm.

    Measured bike frame bottom bracket shell, it is 68mm

    Now, with the new105 crank and new hollowtech 105 bottom bracket, the crank arms will hit the chainstays,

    1) Why does this happen....

    2) Can one put spacers with the 105 hollowtech bottom bracket? (I have spacers from previous mtb bbs which can be used) Some road guys said no, the 105 crank arms are not secured if you put spacers.


    *if more details are required, do tell, and I hope to be able to provide as much as possible

  2. #2
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    Sounds like you are missing spacers. Did the set not come with any?

  3. #3
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    You might need a wider Q factor crankset. Some gravel bikes require wider cranks and cannot run regular road cranksets. I don't think a crank design for a 68mm BB will work with spacers, might not be enough for the arm to clamp onto.

  4. #4
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    The cranks won't work, you can not add spacers to it.

  5. #5
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    delete because double post

  6. #6
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    Quote Originally Posted by Loch View Post
    You might need a wider Q factor crankset. Some gravel bikes require wider cranks and cannot run regular road cranksets. I don't think a crank design for a 68mm BB will work with spacers, might not be enough for the arm to clamp onto.
    I thought so too. But why then did the stock Claris FC2450 work? It is a road crank. And the octa-link bb it came with is 68mm too.

  7. #7
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    Quote Originally Posted by Black Squirrel View Post
    The cranks won't work, you can not add spacers to it.

    The stock Claris FC2450 worked worked with a octalink 68mm bb, and that is why this is confusing. Can you elaborate?

  8. #8
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    Claris is more of a touring group, the Q factor is probably 10mm wider than the 105.

    I run mountain cranks with a 38t 1x on my gravel bike, plenty of clearance and I prefer the wider Q factor.

    Also note, that Q factor doesn't really have any direct relation to frame clearance. Q factor is measured to the outside of the crank arms, not the inside, but the thickness of the crank arms are usually pretty similar, so it can be used for a decent reference.

  9. #9
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    Quote Originally Posted by Black Squirrel View Post
    Claris is more of a touring group, the Q factor is probably 10mm wider than the 105.

    I run mountain cranks with a 38t 1x on my gravel bike, plenty of clearance and I prefer the wider Q factor.

    Also note, that Q factor doesn't really have any direct relation to frame clearance. Q factor is measured to the outside of the crank arms, not the inside, but the thickness of the crank arms are usually pretty similar, so it can be used for a decent reference.

    Wow, you brought a good point Black Squirrel, thank you for bringing this up. So I looked it up
    Claris FC2450 qfactor 152mm
    105 FC5800 qfactor 146mm

    1) Is this what is causing this?
    2) Gravel bike has wider chainstays? (stock tires are 35c)

  10. #10
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    Yep, the chain stays are spaced further apart to allow for more tire clearance.

  11. #11
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    Quote Originally Posted by Black Squirrel View Post
    Yep, the chain stays are spaced further apart to allow for more tire clearance.
    1) Pardon me, is 8mm a world of difference when it comes to this situation?
    2) Spacers cannot fix this as the left crankarm is not secured ?

  12. #12
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    Quote Originally Posted by Loch View Post
    You might need a wider Q factor crankset. Some gravel bikes require wider cranks and cannot run regular road cranksets. I don't think a crank design for a 68mm BB will work with spacers, might not be enough for the arm to clamp onto.
    Thank you Loch, for thinking about the qfactor. As mentioned in the other reply, I looked up the qfactors for both cranks. Even though both are using 68mm bottom brackets, the qfactor difference between the 2 cranks is 8mm.

  13. #13
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    It's how the cranks are made, it's not something you can change.


  14. #14
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    Quote Originally Posted by Black Squirrel View Post
    It's how the cranks are made, it's not something you can change.

    Wow. Again. Clear and concise. Thank you, Mr Black Squirrel.

  15. #15
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    What's the spindle length on the original Octalink bottom bracket and on the new one, and what model is each also? The same goes for the cranks.

    Shimano did funny things with its Octalink bottom brackets, and not all work with all cranks. Also, road and MTB BB's are not interchangeable.

    Tim

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