Ask Josh Anything #18

Look, we love every listener question we get here at Marginal Gains. But this episode, Max King asked one that got Josh so excited he said he was pretty sure he was going to lose sleep over it. Of course, we saved that one to the end, but you'll want to listen to the whole show anyway because we've got great questions about the super tuck and dropper posts, off-label use of lube (and many more lube-related questions), marginal gains and handlebar bags, FKT updates, and more. As always, it's a can't-miss AJA episode of Marginal Gains.

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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  • Finn


    This is a duplicate of a question I left y’all via the text line:

    I greatly enjoy the podcast, and it has helped me accept the reality that my next wheel purchase decision should be based almost purely upon aerodynamics, as opposed to weight! However, this raises a more nuanced series of questions. Here we go!

    Assuming nothing out of the norm with general aerodynamic rim profile/shape, and assuming the use of 28-30mm tires on a disc brake bike, how should someone prioritize overall depth, external rim width, and internal rim width when making an aero wheel purchase? If someone is considering rims ranging in depths from 48-65mm, how much should internal and external rim widths drive the ultimate decision? For example, if one option is 48mm deep, 22mm wide internal, and 35mm wide external, is that preferable to another option that is 54mm deep, 20mm internal, and 29mm external, or a third that is 65mm deep, 20mm internal, and 27mm external? Is deeper always better as a general proposition, or is there a tipping point where the rule of 1.05 and rim widths should be weighted more heavily in light of tire width to be used?



  • Martin Turgeon

    Hi Josh.

    Huge fan of the podcast!

    I myself am doing some video content for a cycling magazine on many cycling optimisation topics.

    For one of our futur episode, I would like to explore and quantify the effects of using cheap and simple homemade fairings. I would be using a Notio pitot tube to get good reliable data.

    I know that you have touched on the subject here and there. I would like to get some input as to what kind of fearing construction would you recommand me to build to put to the test.

    I already have some ideas: a frontal fairing (like a Zipper fairing), wheel covers, front triangle cover, airfoil-like tail behind the rider, splitter plate, etc.

    What would be your top picks that you think we should see the biggest gains? What should be prioritized, what kind of shape (as simple as possible), what should I put some extra attention to when designing the fairings?

    I know that GCN has made a one-off test in a wind tunnel that showed no improvement. But am I wrong to guess that covering the rear triangle on both sides was probably the reason for the results not being better? Why do you think this experiment was so incoclusive?(

    Also, do you have tips on what material should be used? For the concept of the content, I would aim for the cheapest possible solution, but at what point a material that is too flexible might move excessively or start to ripple and disrupt airflow?

    I am all ears for some input on that subject from you (or from anybody in this comment section).

    BTW, you did mention in this episode that you tested a Zipper fairing in the wind tunnel. Do you mind sharing what kinf of CdA reduction it represented?


  • Pierre

    Hi Josh,

    Here is a question for Ask Josh Anything #19 (hopefully) : you probably followed the launch of the Vittoria road tubeless inserts. Seems very promising (though I’ll be curious to see how installation goes with them) but since you are the expert on tire pressure (and now lubes !) and I guess working with the teams you have first hand experience with those inserts, at least in their prototype version… here are a couple of questions : does the change in air volume (since the insert uses some space) requires a change in tire pressure ? To go one step further, would the change in air volume would require to go one size up for tire (let’s say from 25 to 28) in order to get the same ride feel ?

    Anything else we should know about the use of road tubeless inserts ?

    Good to see something new in the road tubeless world and probably making the use of the super fast Corsa Speed 2.0 a little “safer” in term of risk-benefit ratio since it seems changing a flat on the road becomes more or less impossible but finishing with a puncture becomes an option (though a costly one since the tire is going to be ruined).

    Will be super interested in hearing all you have to say on that topic (and what Fatty and Hottie have to say too as this is your great team work/effort that make such interesting and entertaining podcasts !).

    Best regards,


  • Diane Misiura

    Have been using your hot melt method of waxing my chain. Love the wax. When I rewax my chain, do I need to clean it with the degreaser and/or ultrasound or can I just rinse off the old wax with hot water, wipe it down and then rewax it it?

  • Sebastian Rasmussen

    Hello from Denmark.

    Appreciate the podcast, love the depth you go to, to explain the subjects presented to you.

    I remember a discussion Josh had (mainly with himself) about the validity of saving a couple hundreds and going for the CL Roval wheels versus going for the CLX version.

    A bit of time was spent on the importance of bladed spokes.

    Now my question is in regards to a custom wheelbuild i am about to order. I have a quiver-killer bike with a lightweight shallow gravel Wheelset and a set deep section aero Wheelset for Road use.

    I however find myself not wanting to swap wheels and want to try to make an equaly quiver-killer Wheelset.

    I want mid depth rims (approx 45) with around 25mm internal width and plan on running 35mm slicks (or close to) for everything. These are gonna be laced to my favorit hubs from Italien manufacturer Carbon-Ti.

    Now the question is whether I go for bladed aerospokes to go with this or I choose Berd string spokes that I have on my gravel Wheelset now. I tell myself i can feel some added comfort with these but thats on 25mm depth rims.

    So what would you recommend:

    Aero over everything (🤪).

    Lightweight and perhaps some added comfort.

    Thanks in advance, cant wait to hopefully hear you guys give me some clarity!!!

    Best regards


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