27.5 mtb on a 20 frame

Discussion in 'Bike buying advice' started by Simas, Feb 4, 2017.

  1. Simas

    Simas New Member

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    Hello,

    I've been wondering why some MTB manufacturers (e.g. Cube) don't make 27.5 wheels with bigger frames?

    It reads:
    Why is this so? I was considering a 27.5" with a 19-20" frame because 29" just seems a little too big and clumsy for me. Is there something I am missing or should I just check bikes by other manufacturers?

    Thank you
     
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  2. dabac

    dabac Well-Known Member

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    of course you can check other manufacturers.

    But in extreme compression it's like this:
    For riding on anything but perfectly smooth surfaces, it's basically an advantage to have as big wheels as possible. They roll smoother and with less loss of speed over a set size of obstacles.
    What limits the size are things like human proportions, inertia and certain engineering constraints like hub width vs wheel diameter.

    Now, while 26" ruled the roost there wasn't much choice.
    If you wanted a MTB - regardless of your size - 26" was what was available.

    Today we have 27.5 and 29ers, which adds options.
    More riders can - and are expected to - get bikes that are more proportionally sized to their bodies.
     
  3. Simas

    Simas New Member

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    I remember trying a 29er and it just felt awful, though all I tried before was 26".
    I thought that perhaps a 27,5" bike would be easier to control but not sure now since you've said:
    Also the fact that some manufacturers even refuse to make big frames with mid sized wheels, leads me to believe they're just not worth it. Ugh completely lost now..
     
  4. dabac

    dabac Well-Known Member

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    All 29ers aren't created equal.
    Since the wheels are bigger you get different design constraints concerning the frame.
    A 29er frame using straight tubes has to be made a certain length/front end height for the wheel and fork crown to clear the down tube.
    If you want a (fairly) long-travel fork - say 120 mm - it gets "worse".
    Bikes like that tend not to be particularly nice for slow/technical types of riding and/or average size riders.
    29ers with curved tubes and/or shorter travel forks tend to be nicer for average size riders and slow/technical types of riding.

    Depends on the type of riding.
    Smaller wheels ARE lighter.
    Frames CAN be made shorter/lower
    All things equal, a smaller wheel bike will accelerate faster and generally feel more nimble.
    All things equal, a smaller wheeled/framed bike will be easier to toss around and manhandle.
    All things equal, a bigger wheel bike will roll better over lumps and bumps at speed.
    All things equal, a bigger wheeled/longer framed bike will track straighter and ride smoother over lumps and bumps at speed.

    If slow-and technically-difficult describes you favourite kind of riding, stick with 26" or 27.5" if you can find one.
    If fast-and-flowy is a better description, try the 27.5 and the 29ers.
     
  5. alfeng

    alfeng Well-Known Member

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    BTW ...

    If you already have a 26er frame-and-fork, then you should be able to mount 27.5" wheels-and-tires in it ...

    NO guarantees!​

    The BB height will be slightly higher, of course, but not so much that you can't get used to it.

    Choose the geometry-and-suspension-travel on a 26er which most closely matches what you think that you want on a 27.5" MTB.

    To state what may be obvious, while 27.5" wheels-and-tires will easily fit in a 29er frame, the resultant BB height will probably be too low for anything beyond reasonably maintained "fire"/logging roads.​
     
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