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July 5, 2022, 2:08 p.m. -  Allen Lloyd

I don't know the physics, but it makes sense that a smaller wheel can pump a roller more.  A matchbox car will gain more relative momentum rolling down a ramp that a full sized car rolling down the same ramp. My argument would be that it is all feature size dependent.  The bigger the roller the smaller the advantage, so your local trails could dictate how much advantage is created.   Weight is an odd one for me, being a larger (200 pound) dude I generate a ton more momentum down a slope than lighter people.  Bike weight as a component of total bike and rider combo is very small.  Rotational weight differences are fairly small as a % of the total as well.  You can run a carbon 29'er wheelset that is lighter than and al 27.5 setup.  But your cassette plays a bigger role than wheel size.   Turn in and maneuverability gains in geo have made a bigger difference than wheel size.  I know you are saying same geo the smaller wheel is better, but compared to a 10 year old bike the geo is what makes the biggest difference in this area.  I would argue that modern geo evolved to make a 29'er feel more like a smaller wheeled bike in many ways.   At a very high level the larger wheel is acting like a longer lever.  Like you said there are tradeoffs based on wheel size.  I would love for an engineer to do some work on what is actually happening force wise with larger and mixed wheel sizes.  Too much of this stuff is feel and a combination of 1,000,000 other factors, making it hard to really understand what the different sizes actually do.

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