Carbon v. Aluminum Seat Tube Strength-
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  1. #1
    mtbr member
    Reputation: rmalling's Avatar
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    Oct 2005

    Carbon v. Aluminum Seat Tube Strength

    First post in this forum, hope ya'll can throw me some feedback!

    I have broken two aluminum frames (Specialized and Maverick) right below the seat post collar. I have insanely long legs and I rock my seat posts very high. The Specialized break was my fault as I didn't have enough post in the frame. When I had my 1st Maverick ML8, I upgraded to a long ass post that was at least 5 inches below the collar but that too cracked the frame after 2 years. Ethan with Maverick put me on an X-large ML8 frame where there was an extra strong weld where the seat post meets the top tube and he assures me this will hold up to the forces my post is putting on the frame; 2 years in and no issues. But, I'm looking to move to a medium travel carbon 29er.

    Many of the modern frame designs out there tout their 'low stand over height', but all I see is another point of failure for me as the seat post collars on these frames seems to be lower to the ground than on my past frames that I have broken. Even with a long dropper post, will a carbon frame be stronger than aluminum at the seat post tube? What do you all think I should consider when looking for a frame/bike to be sure I don't break a third frame in the same spot?


  2. #2
    Moderator Moderator
    Reputation: Walt's Avatar
    Join Date
    Jan 2004
    There is no generic answer. Some frames will be stronger, some less strong, regardless of material.

    Look for a frame where the seat tube does not extend much above the toptube, and of course if possible the longest seat tube you can find (assuming the rest of the frame geometry is what you want, of course).


  3. #3
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    Reputation: Bigjunk1's Avatar
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    Sep 2016
    Carbon will be weaker than aluminum as far as compression and open end tube strength. Look for a frame with a short seat tube as said above.

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