AJA 26: Sunglasses, Nitrogen, Tire Temperature, and Cyclocross


We rely on Marginal Gains listeners to provide intelligent and provocative questions, and as always, our listeners do not disappoint. In this Ask Josh Anything episode, we re-open the question of hour record attempts, this time considering pros and cons of a negative-split effort. We talk about Nitrogen and its merits of using it instead of air for tires with sealant. We talk about the aerodynamic penalty of tucking your glasses into your helmet vents. Plus tire temperature talk, cyclocross marginal gain tips, and why most BMX bikes don't race tubeless. 

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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  • James

    Hi all, got a question for Josh about hill climbing. I was watching some footage of hill climb challenges (Bike Radar’s most recent hill climb diaries video if you want to take a look) and I was noticing some riders rotate their bars slightly from side to side when putting down power on the steep climbs. This of corse rotates the front wheel a couple degrees left and right repeatedly. Over the full course of a hill climb, I imagine this results in a loss of speed or at least a minor increase of actual distance climbed from that slight wobbling from side to side. How bad is that loss if any, and what are some ways to improve a rider’s stability going uphill? My guess is: it depends.

  • Mike

    A question for Josh. When I follow the instructions at https://silca.cc/pages/how-to-apply-chain-lube to clean a new Izumi Super-Toughness chain using mineral spirits and Chemical Guys Orange Degreaser, the beautiful gold links come out dull, with some silver showing through and a few specks that almost look rusty. Am I doing it wrong? Or is giving up some cosmetic beauty the price I need to pay for efficiency?

  • Marcus Lay

    I’ve been using the hot melt wax for a while now. Super happy with product. Because of my great experiences I’m offering a chain wax service to my customers in my bike shop.
    On a personal note I was wondering when you released the treated chains why you didn’t choose to apply Teflon powder like ceramicspeed. I think molten has the race powder. Is there any benefit to applying some powder as a raceday treatment?

  • Tom

    I have been using Silca hot wax for 3 months now, and absolutely love it! I typically ride around 400km between instant pot hot waxes.
    (1) how many kilometres should one expect on a waxed chain if some of the rides are in wet conditions?
    (2) after experiencing hot wax performance, I got excited and ordered MANY of bags of wax. Do bags of Silca hot wax have a shelf life?
    (3) I have an ultrasonic cleaner, but actually don’t use it to clean the chain between waxes, as I just pour hot water on it and that seems to work well. Should I use the ultrasonic to remove the old hot wax?
    (4) My ultrasonic cleaner is big enough to fit the stainless steel instant pot inner pot inside of it. After heating the wax, would the ultrasonic cleaner to help the hot wax penetrate into the chain slightly better? Should I incorporate this step into my hot wax process?


  • Tom

    My question is on the topic of gravel tires, wheels, and aero:
    For context, I like to run wide, slick, fast rolling gravel tires on both road and gravel, which in my opinion is the perfect choice for road surfaces in eastern Canada, which tend to be a mixture of smooth and poor pavement, and smooth gravel. Average speeds between 30-35kph.

    After listening to a previous episode on CdA, my understanding is a slick 38mm tire set up on a rim like the discus 4540 (40mm external width, 45mm deep) would actually have a better Cd term than a 28mm tire set up on a rim like the Zipp303 with a 27mm external width, as the former set up respects the rule of 105. The A term in CdA would be worse for wide tire as it has a 10mm x 28” greater frontal area than the 28mm tire.
    My questions:
    (1) Is my understanding correct that the wide tire would have a better Cd, but worse A?
    (2) Given the better Cd and worse A, which set up is more aero overall?
    (3) How close are the 2 set ups in terms of aero? Is there an order of magnitude watt difference between the 2 set ups?
    (4) What is the cost in watts of running a tire/rim combo that does not respect the rule of 105, and are running something like a 0.8 (eg. 32mm tire on a 27mm wide rim) which is common in many gravel and road set ups, at speeds of 30-40kph?
    (5) When I watch a race like Roubaix, I’m find it hard to believe no one runs a truly wide tire, say a 38mm ultra fast rolling slick tire (like a reneherse Barlow) set up on a 105 respecting rim (like the 4540 rim), at the appropriate pressure. Will we ever see this?


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