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Path: news.eternal-september.org!eternal-september.org!.POSTED!not-for-mail From: Frank Krygowski <frkrygow@sbcglobal.net> Newsgroups: rec.bicycles.tech Subject: Re: RE: Re: RE: Re: Patching TPU innertube Date: Mon, 30 Dec 2024 23:07:58 -0500 Organization: A noiseless patient Spider Lines: 53 Message-ID: <vkvqmv$22g80$1@dont-email.me> References: <vkahvt$t3o3$1@dont-email.me> <vkbp2i$17klb$1@dont-email.me> <lt5ah7Frbs0U1@mid.individual.net> <vkjtn0$31qda$2@dont-email.me> <eevqmjdnt6rj741eks86nd0p3lfuan26o2@4ax.com> <lt63r7Fp12U1@mid.individual.net> <vkl5qn$38s8g$12@dont-email.me> <ECWbP.19860$zX7.10220@fx37.iad> <vkq1dc$iqtc$4@dont-email.me> <YVecP.26368$5c34.15470@fx47.iad> Reply-To: frkrygow@gmail.com MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Injection-Date: Tue, 31 Dec 2024 05:08:02 +0100 (CET) Injection-Info: dont-email.me; posting-host="1a2e4f2630296e8d16d766962a7cf3aa"; logging-data="2179328"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX18SDUya1d9UJwlSNw1RfA+8POgHVyAiLe4=" User-Agent: Mozilla Thunderbird Cancel-Lock: sha1:eKlD9GZBAjzduoTnX11sLz2paxY= In-Reply-To: <YVecP.26368$5c34.15470@fx47.iad> Content-Language: en-US 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? Rolling resistance of tires is almost always a tiny component of this calculation. Jobst would have taken you apart for that comment. Jobst would have understood it. -- - Frank Krygowski