Re: Patching TPU innertube

On 12/29/2024 6:58 AM, zen cycle wrote:

On 12/28/2024 6:25 PM, Frank Krygowski wrote:

On 12/28/2024 12:32 PM, cyclintom wrote:

On Thu Dec 26 22:10:15 2024 Frank Krygowski  wrote:

On 12/26/2024 5:32 PM, Roger Merriman wrote:

>
The issue for me is that while Gravel tires absolutely do feel more supple
with TPU tubes, these are tires while some claimed sidewall protection,
these aren?t like Trail etc MTB tires which have reinforced noticeable
stiff sidewalls is aren?t floppy, each tire is 1kg or so.
>
Hence I wonder if a upgrade to TPU tubes would be noticeable...

>
>
I'd be interested in people's personal measurements of differences. If
someone here had access to some long, gentle downhill and kept track of
terminal coasting speed using different tires, different tubes, but
otherwise identical equipment, terminal coasting speeds might be good
information.
>
It would be best to test in consistent temperatures and with negligible
wind, of course.

>
Frank, what do you believe the difference in terminal velocity would be with 1/2% decrease in rolling resistance on a 5% slope which is almost entirely set by the tires? For crying out loud, you claim to be a mechanical engineer! Aerodynamic drag would be 100 times the rolling resistance.

>
I'm breaking my recent resolution to skip responding to you, Tom. It's normally a futile endeavor.
>
But as to your question: Aerodynamics was the specific reason I specified a _gentle_ downhill. I think the best might be one that would give a terminal speed of 12 to 15 mph, since at those speeds aero drag is at least roughly the same magnitude as rolling resistance.

 I question this: I suspect resultant drag at 15 MPH is significantly higher than the resultant drag from rolling resistance, but since the resultant drag 15 MPH in terms of watts is likely in the low single digits, the difference between that and a few tenths of a watt from rolling resistance is imperceptible.
 

>
And yes, I expect the differences would be difficult to detect. Which raises the question: If the differences are difficult to detect, are they really worth worrying about? Are they really worth the expense, and the hassle of changing one's equipment?
>
If you're racing, perhaps so. Otherwise, it seems not.

 Even if you're racing, the law of diminishing returns applies heavily. For a pro, certainly it matters. For us amateur age groupers, benefits from tire selection get lost in the noise.
 

>
If you get to your coffee shop fifteen seconds earlier, do they give you a prize?   ;-)
>

"benefits from tire selection get lost in the noise."

For me as well and I think probably for most of us. Excluding the absolute junk at the lower end of the range is plenty enough selection for an acceptably pleasant ride.
--
Andrew Muzi
am@yellowjersey.org
Open every day since 1 April, 1971