AJA 29: Hot Wax on a Hot Day


It's an Ask Josh Anything episode! We talk about The Rule of 105, the extent to which "bigger is better" is true for fairings, whether tire inserts need to be factored in when using air pressure calculators, why you might get conflicting recommendations from different air pressure calculators, how many watts a slow-turning old derailleur cog might cost you, the challenges a hot day might bring to your waxed chain, and more. So much more. Some people might say too much more, but we are not those people, and we're betting you are not either. Don't miss this episode, and keep your questions coming!

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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  • Luke Davey

    Hi MGPC team,

    Firstly I’d like to say a big thank you to you all for your efforts in exploring the right-hand side of the decimal point, and the quality and engaging dialogue on the podcast.

    I have a question for Josh regarding (surprise surprise) waxed chains.
    Apologies if it’s a bit long and technical – I’m currently out of action waiting for back surgery, and waxed chains are smoothly and efficiently occupying all my thoughts.

    I would like to know what are the key determining factors regarding the longevity of a hot melt wax application beyond just km (miles). Assuming other variables are kept the same (drivetrain make and model, temperature, dirt and water contamination etc); what of the following are the most important factors:
    1. Power: do chains transferring the same power at different chain speeds last the same amount of time ? For example one is high torque and low speed and the other is the opposite.
    2. Energy: do chains transferring the same energy over different time periods last the same amount of time ? For example one is high power and short timeframe and the other is the opposite.
    Maximum Force:
    3. Chain cycles: does the number of cycles a chain does through the drivetrain affect the lifespan eg could a chain transmitting low power at low torque continue with adequate wax protection almost indefinitely?
    4. Chainline angle: does the chain being at an extreme angle (eg extreme ends of the cassette) affect the waxing lifespan ? Or does frequent changes from one extreme to another affect the waxing lifespan ?

    And finally, are there any relationships, generalizations or rules of thumb for the above questions ?

    Once again, many thanks for your efforts and insights.

    BTW – I’ve been running Silca Super Secret on my road bike for just over a year now and am completely converted to the system. I originally converted to the system for the cleanliness after my toddler touched the chain and then proceeded to wipe dirty oil on the walls inside the house.
    In the time I’ve been using wax, I’ve done 8,500km with average re-waxing at 365km internals. I periodically measure chain wear doing a full chain elongation measurement following a boiling water flush to remove any residual wax. I’ve recorded zero wear in that timeframe. With the availability and cost of parts nowadays, plus my toddlers continued interest in the chain, I’ll be continuing with this system.
    THANK YOU!!!

    Kind regards,

  • Matt King

    Hi Josh. Here’s a question related to working with the pro peleton (while I watch the strange Giro Stage 20 TT – a good topic for a discussion in itself!).

    Is there any scenario where aero either doesn’t matter, or isn’t worth chasing every gain? I’m thinking of situations like a domestique or lead out rider acting as a wind break for their leader/sprinter – surely creating a bigger wake is beneficial from a team perspective? Or, a sprinter/domestique on a time trial stage where they are not in contention for GC or stage win – why do they bother?

  • Steve

    Josh, Respectfully, ENVE started publishing their tire pressure guide (it’s not a calculator), years before the ETRTO got involved in recommending max tire pressure for hookless rims (2021) and the numbers for wheels like the SES 4.5 (originally called the 4.5 AR introduced in 2016) haven’t changed. Additionally, ENVE doesn’t agree that 72psi is the recommended max tire pressure for their hookless rims (80psi is their recommended max) and lists tires compatible with their rims based on internal blowoff testing at 150% (120psi) minimum. FWIW, SRAM’s tire pressure calculator recommends pressures much closer to ENVE’s than Silca’s. When I look up pressure recommendations from all three companies for tires and wheels I test, Sillca is often 10psi or more higher for my 150lb/68kg weight and l bounce around like crazy (added vibrational rolling resistance beyond the “break point”?) at the Silca pressures, let alone having a less comfortable ride. Your Rule of 105 is also an anachronism in the eyes of wheelset engineers around the industry. For more on this see my article on the topic https://intheknowcycling.com/how-wide-wheels-wide-tires-make-you-faster/ Steve

  • Rob

    Hey Marginal Gains Gang. I have a lot of thoughts on hookless rims, and a couple questions. I’m one of the rare people who uses a hookless rim brake wheelset. Because of this the largest width tire I can run is 28mm (frame and rim brake caliper clearance). My total system weight is over 215 lbs. The recommended tire pressure from the Silca Pro Tire Pressure Calculator is 81/79 PSI. This tire pressure is considered unsafe according to ETRTO recommendations. To achieve the “safe” pressure of 73 psi (5 bar) the system weight would have to be less than 140 lbs. Most cyclists, even most adults, are well over this system weight. According to these new ETRTO recommendations essentially everyone either shouldn’t use hookless rims with 28mm tires or should use 30mm or larger tires on hookless rims, presumable with a disc brake bike that can fit that wide of a tire. This news is very frustrating to anyone who is currently using hookless rims with 28mm tires. According to my wheel manufacturer, Giant, it is safe to run any tire on their approved tire list with their hookless rims (https://www.giant-bicycles.com/global/hookless-technology). Who do we trust here; the ETRTO or the Hookless Rim Manufacturers?

    Continental GP5000 S TR is broadly considered the fastest tubeless race tire at the moment and it’s largest width is 32mm. Where is the “sweet spot” for tire width on hookless rims in regards to aero losses (105% rule) and rolling resistance/tire pressure? Is it larger than 32mm?

  • Howard Ryujin

    Thank you for this interesting and informative podcast! I switched to Silca’s hot wax and get much better life out of my chains. Given that much of the wax on the surface wears off quickly, I’m wondering what impact that has to the lifespan of the rings and cogs. I recently had to replace my full drivetrain and I’m not sure if that is because I waited too long to change the chain (it was between 0.5 and 0.75% wear), or if my rings and cogs will wear faster as there is more metal-on-metal contact with wax vs a wet lube. Looking forward to your response!

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