Ask Josh Anything #12

We are happy to report that we continue to seek questions Josh is unable to answer, or at least unwilling to try. We regret to announce that we have so far failed, in spite of the fact that in this episode we expanded our universe of acceptable questions to include how to make electric scooters more aero. Josh was, in fact, distressingly excited by this question.

We (or more to the point, you) also asked questions about:

  • Silca's new Super Secret Lube: To be honest, we spent a few minutes asking about this lube, and then about half an hour talking about lubes in general, the importance of lubing, and the proper way to lube.
  • Pressure calculator vs manufacturer specs: What should you do when the Silca tire pressure calculator gives you one pressure recommendation, but the tire manufacturer gives you a much higher minimum recommendation?
  • Pressure calculator and tube type: Does the way you keep the air in your tire (latex tube, butyl tube, tubeless, tubular, etc.) matter in the pro tire pressure calculator? If so, how much? And if not, why not?
  • Tire hysteresis and contact points — we have some followup questions for Josh about his recent conversation with Path Less Pedaled.

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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  • Tom

    For the next AJA:


    1) I seem to remember a quick conversation about aero pedals I’d love for that to be rehashed.

    2) Has Josh gone as far as suggesting pedal rebuilds for events like the hour record? If so, what type of gains were seen?

    3) If the casual marginal gainer were interested in optimizing pedals: What brand do you start with and why? What is getting replaced and with what? What grease? What’s the life expectancy? (e.g. only good for the hour record, 100-200 miles, 1 season).

    4) If "aero is everything: should there be some effort to make the pedal spindles aero as well or is that area just too “dirty” to experience gains.

  • John Morrell

    For the next AJA: I have a few different drive trains on my bikes. I use paraffin wax on all the chains. I have the perception that my 3×8 is much quieter when suffering uphill in a my lowest gear vs. my 2×11 or 1×12. Cross-chaining has been shown to be less efficient and yet people pitch the weight savings of fewer chain rings on the crank. Also, the testing I’ve seen seems to be run at approximately constant power. Since Josh taught us that life is nothing if nonlinear, I would be curious to know if anyone has run a power profile that is non-constant. What if the efficiency is worse at peak watts trying to stay with the bunch over the top of hill ? At 5% loss, I’m going to lose 15 watts from 300 at high steady power, lots more for 1 minute efforts. What if it’s worse than 5% loss? Car companies use a driving profile for mileage estimates. What about testing drivetrains across a range of power inputs that reflect actual riding power output, and assessing where efficiency is most important to riders? Maybe the losses are less load dependent so that the chain efficiency improves under high torques… Wish I knew.

  • ron

    in episode 10 you mention that there is virtually no difference between a latex tube in a tubeless and a straight tubeless set up. What would happen if you added sealant to a latex tube in a tubeless tire? Would you get similar rolling resistance and added small puncture protection?

  • Tim H

    Hi Josh, Fatty, Hotty,

    I have a question regarding fairings. The talk about the fairing on an electric scooter in AJA#12, got me thinking if fairings could also be used on time trial bikes. I do some triathlon racing where UCI rules are not important, and am thinking about building one. Would making a fairing around my arms and hands give me an aerodynamic benefit?

    Some sub-questions:

    - Would making a fairing generally result in better aerodynamics, or can this go either direction (faster or slower)? This can be tested using the Chung method, but if it is likely to give a slower result, I might be less tempted to invest the time to build a fairing.

    - Are there any other areas which would benefit more strongly from fairings (e.g. behind the seat)?

    - Would the increase in frontal area (the fairing removes the gap between my arms) still result in a lower overal CdA?

    - What shape of the fairing would be beneficial? (I suppose a parabola with the sharp edge pointing in the direction of travel?)

    I hope you can spend some time discussing this topic.

    In any case, keep up the good work on the podcast! I really enjoy the show!


  • Jeff vdD

    Q for next AJA: I just received my Silca Super Secret Chain Lube. As a fellow “J,” why is the “J” in Josh’s name backwards?

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