Ask Josh Anything #006

The ongoing "Ask Josh Anything" series is back from Summer vacation and we've got a fun — and surprisingly informative — set of questions for Josh, including:

  • What marginal gains are made by following the TTT instructions in a pre-TdF video by Team EF?
  • When you've got a tailwind, is it better to still make yourself as small as possible, or should you sit up and try to take advantage of the wind behind you?
  • What's going on when the dish changes the first time a tire is mounted on a new wheel?
  • Some riders claim their bike feels faster and lighter on climbs when they move their bottle to their jersey pocket. Is there any merit to this, or is the effect in fact the opposite? Or neither?
  • FFWD claims to have made the fastest wheel ever. Is it possible to legitimately make this claim?

All this and an in-depth discussion of what happens to your aero-ness when you grow a beard (with a side discussion on types of beards), in the show that makes a big deal about the little things, and how those little things can be a big deal.

Got a question you’d like to ask? Text or leave a voicemail at the Marginal Gains Hotline: +1-317-343-4506 or just leave a comment in this post!

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  • Michael Richard Hotten

    Love your question Rob. I will bring it up with Josh. In the meantime, have you considered trying the “Chung Method” to test your wheel compound theory? – Hottie

  • Dave


    Another mechanical engineer here LOVING your podcast. Rated 5 stars and telling my friends.

    A question I’ve been wrestling with in my head lately relates to power demands based on grade, with the motivation behind the question pertaining to gear selection during training on an indoor trainer in ERG mode. My theory is that all watts are not created equal, my logic is below.

    In short:

    1. How is power actually calculated?

    Of course, strain gauges in the crank arm measure strain in the material, so that Force -> Torque -> Power can be calculated. Sampling this strain many times over the duration of one revolution of the crank gets you your force vs. angle measurement. Averaging that can get you your average power, or something like that.

    2. How do the power demands within a single pedal stroke change with respect to grade?

    You spoke in one of the recent podcasts about micro accelerations. When climbing, you’re fighting these micro accelerations a lot more than if time trialing or riding on a downhill. My thought is that 300watts at 90rpm climbing is physiologically different than 300watts at 90rpm time trialing or descending, because you have to overcome these micro accelerations (FBD shows this concept easily as positive grades have a higher net deceleration in the absence of a pedaling force). Again, my theory is that all watts are not created equal. 300w @ 90rpm climbing must be different thatn 300w @ 90rpm descending.

    3. If we now understand the physiological differences between power demands at various grades, what gear should we be training in in ERG mode on an indoor trainer?

    The root of my question is cycling on a trainer in ERG mode. Gearing must matter in my opinion. A low flywheel speed (small chainring up front, large cog in the rear) simulates climbing with micro accelerations (higher braking force on the flywheel, lower flywheel speed). A high flywheel speed (large chainring up front, small cog in the rear) simulates a TT or descent (lower braking force on the flywheel, higher flywheel speed). 300W in erg mode in different gear selections must be physiologically different, right? All watts are not created equal, right!?

    Can you please explain the physics behind the phenomenon I’m wondering about? Help me sort out this confusion that I have!

  • Michael Brooks

    What’s better 4 separate cables or tape or shrink wrap brake and gear cables. P.S. interesting stuff on shaving a trip strip on your legs.

  • Matt King

    Hypothetical question: (Thinking back to the early days of triathlon for example, where wheels as small at 24" were used with success)

    If you could start from scratch with no legacy, what would be the best road bike wheel size? Where does the optimum balance of aerodynamic drag, lift, weight, rolling resistance and bump compliance lie?

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