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From: AMuzi <am@yellowjersey.org>
Newsgroups: rec.bicycles.tech
Subject: Re: Patching TPU innertube
Date: Sun, 29 Dec 2024 11:55:24 -0600
Organization: Yellow Jersey, Ltd.
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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