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Path: ...!feeder3.eternal-september.org!news.eternal-september.org!eternal-september.org!.POSTED!not-for-mail 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. Lines: 84 Message-ID: <vks2ed$132mg$6@dont-email.me> References: <vkahvt$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$4@dont-email.me> <vkrh1q$vitp$2@dont-email.me> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Injection-Date: Sun, 29 Dec 2024 18:55:25 +0100 (CET) Injection-Info: dont-email.me; posting-host="24403ef2cd02895745468a3c60737ebc"; logging-data="1149648"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX1/Bb/85vnbxaEvx0BfwrLAx" User-Agent: Mozilla Thunderbird Cancel-Lock: sha1:4fE501T9omx9hsKVFG4I0N5Tuls= Content-Language: en-US In-Reply-To: <vkrh1q$vitp$2@dont-email.me> Bytes: 4459 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