Ask Josh Anything #008

We're back with more proof that we're willing to ask Josh practically anything bike-related…and that he's willing to take practically any question seriously. In Ask Josh Anything #008, we talk about what gas you should fill your tires with, the challenge of planning for endurance ride air pressure loss, marginal gains and Kipchoge's sub-2-hr marathon, which pedals are most aero and whether aero pedals matter (they do!), whether aero adjustments could make a difference in downhill MTB races (they could!) and —as always — much more.

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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  • Joao Godinho


    Thanks so much for bringing us this amazing podcast, the only one that I can’t ever wait to listen!

    My question is in regard to frame compliance efficiency.

    As I understand, there is no conclusive data to prove that laterally stiffer frames are more efficient on power transfer, is that correct?

    Being so, as an average carbon frame user on the really rough tarmac of southwest Ireland, I’m wondering if a more compliant frame material, like steel or titanium, would actually improve power efficiency.

    Despite of being very picky with tire pressure, I had the chance to ride a titanium bike with a similiar geometry and slightly more air on the tires, and found it much more supple.

    Is there a level of roughness of tarmac where the compliance of steel and titanium frames would provide more efficiency than carbon, regardless of using the most adequate tire pressure? Because that’s what I felt.

    Thanks !

    Joao, from Bandon, Ireland

  • HÃ¥kon Hvistendal

    Hi Josh,

    First – thank you for THE BEST cycling Podcast – I have a question or two rear about disc wheels.

    Do I get any gains, as an amateur cyclist, running a rear disc Whee vs. f.×. Zipp 808l?

    I ride a lot of ITTs and offen see riders running discwheels even though their average speed are no faster than 30 -32km/h on a flat course.

    How fast should one rider ride before there is an aero advantage?

    How steep should a climb be, before the rider would be better off with lighter rear Wheel?

    Really hope you will bring this up in your podcast :-)

    Best regards

    HÃ¥kon (Houkon), Denmark, Scandinavian, Europe ;-)

  • Jeff Beeston

    I have a question regarding aero benefits in triathlon versus time spent in transition. Say in an event like an Ironman or Half Ironman, how much time is worth spending to gain aero effects such as shoe covers? Understanding it could likely take a couple of minutes to get the covers on and then shoes off after the bike is there enough gain to offset. Similarly when thinking about the tri-suits and benefit of a super tight fit, understanding one will be running for a long time following the bike how much comfort is worth giving up for time – or rather how big is the trade-off?

  • James

    Love the show! This is a question for Josh and Fatty (Hottie can weigh in too)

    I am a true fat cyclist (250 lbs) and have long had a goal to ride White Rim in a day (100 miles, 7,500 feet elevation, mostly bumpy sometimes sandy dirt road). My current ride is a Surly Krampus fully rigid 29 plus bike. The current tires are 29×3.0 WTB Ranger light (900 grams) run tubeless. In past rides on White Rim I’ve averaged around 10-11 mph over 50-75 mile days.

    With respect to my goal, please help me weigh the rolling resistance and aero considerations (and weight I suppose) of the current tires vs. something narrower and lighter (e.g. Rocket Rons at 600 grams). The smaller tires are presumably more aero but would be run at higher pressure.

    Second question: Costs and benefits of getting a suspension fork (or a lighter rigid carbon fork).

    Or, should I get a different bike? Assuming I’m not too budget constrained, what is the ultimate White Rim killer bike?

    What does the collective scientific knowledge and first hand expertise on White Rim say on these matters?

    Thanks, James

    Salt Lake City (formerly Alpine and really missing such great access to trails…)

  • Mike Williams

    Here is a new question for you:

    When I look at the current crop of top-end TT bikes, especially with 3D printed cockpits that integrate the extensions and extension with the arm, about the only part of the bike that hasn’t seen any real aerodynamic thought seems to the the seat. It seems that anything you could do to reduce the low pressure area behind the rider would help reduce drag. Are there any tricks you would suggest or has anyone doe anything with this?

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