Ask Josh Anything #16

Re the question on damping in a frame, was it around the idea of hysteresis of the frame material? e.g. some materials (say steel) might be low hysteresis and spring back all the energy you put into flexing them, while others (perhaps composites) may be higher hysteresis, absobing energy, hence providing a damping effect.

Hi MG,

Thanks for a great podcast! I’ve got a 3 months old daughter and during late nights I’ve listened through all episodes (they have been life saving).

One of the things I love about the podcast is that it often leaves you with more things to ponder after each time.

Here comes my questions for Josh:

- I’ve bought into the hot wax cult. But the first time I tried to melt the wax I did it in a water bath and managed to get some water into the wax. It stayed on the bottom so I tried to raise the temperature slightly to try to boil the water away. It seemed to work but I think I saw the tungsten-particles gather in the water bubbles instead of mixing in the wax. What do you think, have I ruined the batch of wax or could I reheat and try to mix up the tungsten particles again?

- I’m interested if you know of aerodynamic research done on other rim profiles than the ‘normal’ toroidal shape? E.g. the FFWD DARC profile and how the rule of 105 applies to these profiles?

- When aerodynamic benefits is discussed yaw-angle is always mentioned, but I have a hard time to translate the yaw-angles to real life situations. Is low yaw (0-10 degrees) mostly experienced in straight headwind?

- connected to yaw-angle. In very low yaw, how big is the difference between modern aero bikes and older bikes. E.g. Older 1” head tubes must have a lower A while the modern bigger head tubes have a lower Cd. So in which conditions do modern aero frames gain the biggest advantage?

- last one connected to lube. What other parts of the drive train would be beneficial to hot wax? :) Bushing? Bottom bracket bearings? Head tube bearings? Dip the whole bike in a bog tub of hot wax?

Thanks again for a great podcast,

Alex

Hi guys!

In the beginning, I have to say, I truly love your podcast. So many useful information based on true science and experience, I can’t praise you enough!

I’ve got two questions for you on different subjects.

1. I’ve been wondering about aero disc rotors in road bikes.

I’m sure you’ve seen so many pro’s went with XTR rotors in TDF instead of Dura Ace. Some said it was due to lighter weight, others that it was due to XTR ones being stronger. As for the weight savings, those are whopping 17g on a 160/140m set. I’m not sure this can be even counted as a „marginal” gain, when thinking of 70-80kg whole bike+rider system. Assuming they actually did it for the weight savings, they simultanously ditched the aero benefits of Dura Ace rotors. I’ve been wondering, whether they did the right thing, or maybe more aero rotors don’t actually matter that much because of their small size? There are also some other rotors in the market, like Galfer CL road rotors, which save around 40g on a set compared to Dura Ace. It doesn’t seem like much, yet it makes a tiny bit more sense as it saves around 20% of the part. So, my question is, would you consider trumping the aero gains of aero rotors for such weight savings, lets say for a mountain stage?

2. I’ve been waxing my chains for a few months. It’s great on the outside bikes, but I’m kind of tired of wax flakes on my indoor trainer matt and trainer itself. I’ve been thinking about buying the synergetic lube for the trainer. There would be no external contamination, except for the metal particles from drivetrain wear, so the re-lubing intervals should be very rare. How many indoor training hours would you expect of Synergetic? Would you do that switch?

Thanks a lot!

Matthew

Well guys another great episode! I was wondering if anyone has ever checked chain friction and lube effectiveness by using thermal imagining with high sensitivity thermal cameras? I am thinking that friction tends to dissipate energy as heat so lower friction would be lower generation of heat. Also for durability as a the friction starts to increase due to loss of lubricity the temperature should start to increase. So by watching this in the time domain for a constant speed/ load set up one should in theory be able to see the change over time in friction as well as grade the quality of lube against another. thanks

Josh – you talked Damping at the 50 minute mark of the bifurcation and marginal gains in regards to mountain bikes!