Similarly to what others have already clarified, I was writing on the basis that, on average, a generic latex tube tests faster than a generic plastic tube. If two particular models test the same, then in this particular case, the two tubes should have the same "damping coefficient". This is what manufacturers of plastic inner tubes should be shooting for (or even targeting being faster than latex). Together with engineering the wall thickness appropriately, achieving this will come from their own recipe for polymer production and e.g. how it affects the interaction between the polymer chains (for instance this could be for creating more bonding cross-linking).

To continue de-conflating terminology, perhaps part of your original problem with the concepts comes from the perception of the two types of inner tube in the hand. Latex tubes are very flexible – not much force is needed to strain (i.e. "stretch") them by a certain amount. They are also very elastic (in the technical sense), in that they can be strained significantly before reaching a limit and suffering permanent damage or distortion. These two properties will make them feel "stretchy". I'm guessing that plastic tubes, in contrast, are both stiffer (more force needed for a certain strain) and cannot be strained as much before reaching a limit (less elastic). This will make them feel more rigid in the hand. However, while these contrasting properties can make a functional difference both to ease of installation and to the ability to conform to objects penetrating a tyre, they are not directly relevant to energy loss when riding. This instead derives from their respective "damping coefficients". Note that, given their very different stiffness and elasticity, likely this "damping coefficient" would be very hard to judge "in the hand". Indeed, the perception of their properties in the hand could be misleading, with what might seem like a logical conclusion from it being incorrect. This could be somewhat akin to the common misconception that increasing spoke tension makes for a stiffer wheel...

thank you. you're a good teacher. it all makes sense. i guess the question i had - and still have, even after the deconflation of terms of art - is that it seems to me that if the plastic is less elastic, it lacks the capacity to, as you put it,"conform to objects." it is less likely to intake a road imperfection; more likely to roll over it. if both tires are inflated to the same pressure - exhibit the same hardness, the same resistance to deformation - it may well be that this is not an important feature of the tube. but obviously there is deformation of the tire, or else there would be scant benefit to the pneumatic tire, and obviously the deformation of the tube is an issue with which to be reckoned, as directly relates to the capacity of the latex tube to outperform a butyl tube.

i don't mean to be pedantic. i've been riding bikes since the 1970s and i've never seen a plastic innertube. now i have 2 pairs of them, that i'm getting ready to part with, and when you hold these in our hands what you realize is that there is nothing even close to the elasticity as you have with a latex or butyl tube. i am very surprised it tests as well as it does.

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Dan Empfield
aka Slowman

When you write "elasticity" here, do you mean that they are much stiffer – i.e. harder to stretch a certain amount – or that you cannot stretch them nearly as far? Curious.

I'm going to need some pictures of the bike or CAD files for those 3D printed parts :p

I'm using plastic tubes in one of my cycling applications and anecdotally it's a less supple ride than tubeless on the same surfaces. Noticeably. No leak down though. N=1.

Eric

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Eric Reid AeroFit | Instagram Portfolio
Aerodynamic Retul Bike Fitting

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I use these polyurethane tubes for some months on my training road bike. The tubes hold pressure much better than latex, however I think, thick butyl tubes still hold pressure a little bit better.

I tested them on my drum test rig. Rolling resistance is between butyl and latex, just like others have tested too. But in my tests they are closer to butyl than to latex (I would expect some damping from a thermoplastic). And they behave more like butyl than like latex, i.e. they have a stronger dependance from speed than latex (18-55km/h) (look at this interesting paper from Baldissera 2020 on rolling resistance). In applications where rolling resistance is king I would choose latex.

Interesting...did you mean to add a link to the Baldissera paper? I'd like to see that.

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http://bikeblather.blogspot.com/

Along these lines........what out there would be any better at all if you had to pick something mechanical (not electronic) as a frameset better than my old Felt DA? Especially for yaw angles when avg about 28mph on flat land.

About the only thing I've remotely been interested in price wise is the RTTC champion's Ribble TT bike. It looks a smoking deal at $1500.

I lost an auction on a used P5 frameset, but probably a good thing. Looking back, it suspiciously looked like a probably Chinese faker.

Reason I say not electronic is that I really can't afford the $1200 bump in price.

A >2011 Da. ;) The P5 is a sure fire winner, though.

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My YouTubes

Haha. There's actually a few brand new 2015ish DA's on Ebay recently for like $1100 or so. I would be into the stupid stem crap again though with Felts that I don't care for.

I made a custom deal myself in my shed for my DA to get rid of that trash.

That's not bad. I had no luck finding any NOS in my size. I picked up another 2011 and while I am thinking I might have paid a bit too much, it did come with a bunch of extra crap...like the now hard to find 0º rise 110mm stem. The Da is a fast setup with the right bar.

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My YouTubes

P. Baldissera et al., Experimental Comparison of Speed-Dependent Rolling Coefficients in Small Cycling Tires, Tire Science and Technology, April 2020, https://doi.org/10.2346/tire.20.190207

I run a PDQ version open mold bar with all Aerocoach bars and cups. Aeria Ultimate stem. Pretty slippery. I even replaced the hex head bolts with rounded pan head hex bolts for that 1/10th of a watt. Tririg front brake. My custom stem mount allows about 1/2” lower front end than the spline stem.