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From: zen cycle <funkmasterxx@hotmail.com>
Newsgroups: rec.bicycles.tech
Subject: Re: RE: Re: RE: Re: Patching TPU innertube
Date: Tue, 31 Dec 2024 07:29:33 -0500
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On 12/29/2024 11:38 AM, cyclintom wrote:
> On Sat Dec 28 18:25:31 2024 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.
>>
>> 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.
>>
>> If you get to your coffee shop fifteen seconds earlier, do they give you
>> a prize?   ;-)
> 
> 
> 
> 
> What is a "gentle" downgrade? are you unaware that a bucycle will accelerate to the speed at which opposing forces equal the accelerating forces? 

no, I'm sure frank needed you to point that out....lol

> Rolling resistance of tires is almost always a tiny component of this calculation. Jobst would have taken you apart for that comment.

Considering that's exactly what Frank is stating, I'm pretty sure Jobst 
would be in full agreement. I would have _loved_ to hear Jobst's take on 
your claim that you rode a dent out of your top tube, or that bike shops 
pre-stretch their cables, or any of the other inanities you pull out of 
your ass.