Re: Patching TPU innertube

Frank Krygowski <frkrygow@sbcglobal.net> wrote:

On 12/29/2024 7:58 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.

 
True, the slower the terminal speed, the better for judging rolling
resistance, or attempting to separate it from aero drag.
 
Part of my thinking was to test at the rider's typical riding speed. I
suspect almost all of us here typically ride faster than 12 mph. In any
case, results of tests at one's typical riding speed would give the best
indication of the difference tires, tubes, etc. would make for that rider.
 

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.

 
Agreed. Assuming one stays away from really terrible tires, that is.
 
 

Kinda depends on folks intended use, cheap road tires are okay, as dry
weather commute/training tires tend to be heavy and maybe a bit sluggish,
but also fairly robust.

They loose on rolling resistance and grip but then some premium winter
tires like the Gatorskins are similar lack of wet grip, to the extent
“Skaterskins” is one of their nicknames!

I’d say that a tire upgrade makes the biggest difference on any bike, off
road it’s particularly important and noticeable, and fairly cost effective,
though off road or MTB it is a more complicated than road, or even gravel
tires.

Roger Merriman