Практика Shadowing: How Tire Rolling Resistance Affects Cycling Speed ? - Изучайте разговорный английский по видео
Создание урока...
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What is rolling resistance and why should you think about it on the bike?
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Rolling resistance is, quite simply, the energy that is lost as a tyre rolls along a surface.
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The energy is mostly lost because of the constant deformation of that tyre against the surface.
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Now, whilst paying attention to rolling resistance is important, it's not actually the biggest resistance factor when it comes to cycling fast.
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Air resistance rises in a squared ratio with increased speed.
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At a speed of 20 kilometers an hour on a level ground, air resistance has already become the main resistance force.
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And the faster you go, the more air resistance increases exponentially.
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So before even thinking about rolling resistance, get aero.
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Acceleration energy is also expended, for instance, the weight of the wheels is of great importance when this mass has to be brought up to rotation.
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Then when riding uphill, the main resistance force to be overcome is the gradient resistance.
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This is basically the additional resistance added by fighting gravity.
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And in addition to these, there are other friction resistances in the chain, the bottom bracket, and other rotating parts.
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Now, in a well-serviced bicycle, these represent a very minor part of the total resistance.
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So, should you just ignore rolling resistance then?
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Well, no. Because improving your rolling resistance may be the cheapest
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and easiest upgrade you can make to your bike to go faster.
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You can improve all the others by getting aero, by getting a good bike fit and spending the time getting used to it, by getting aerodynamic and light frame,
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by getting some aerodynamic race wheels, and even by upgrading the bearings to maybe ceramic bearings.
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But you can get big gains simply by upgrading your tires and improving your rolling resistance.
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And of course, pumping those tires to the right pressure.
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It's pretty simple.
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A tire with a higher rolling resistance will require more power
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to attain the same speed than a tire with a lower rolling resistance, will require less power.
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So what factors affect the tyres rolling resistance?
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Tyre pressure.
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On a completely smooth surface the following applies.
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The higher the inflation pressure the less the tyre deforms and thus the lower the rolling resistance.
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However on an imperfect surface which we are always riding on lower inflation pressures cause the opposite, lower rolling resistance.
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Imperfections in the road on a very hard tyre will cause bouncing and skipping and increased resistance, not to mention the toll that takes on the rider in terms of fatigue.
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Whereas a tyre with low inflation pressure can adapt better to the rugged surface.
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It sinks into the ground less and absorbs imperfections rather than pushing against them and bouncing off them.
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And so with a softer tyre the whole rotational mass is held back much less on the uneven surface.
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Tire width.
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At the same tyre pressure on a smooth surface a wider tyre will have lower rolling resistance than a narrower tyre.
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This is essentially because a wider tyre with the same pressure actually has an effect of higher pressure
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because a wider tyre with a higher air volume will have a higher casing tension.
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Basically the wider tyre will be harder because it needs more air to fill it and the contact patch, the bit of the tire touching the road, will be smaller and wider, decreasing the rolling resistance.
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But again this only holds true on a smooth surface.
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On an imperfect surface with the pressure corrected for the width to get the tire to the right hardness, the contact patch on the road for a wider tire will be shorter and wider than a narrow tire,
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decreasing the rolling resistance.
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Importantly the wider the tyre will have more versatility and the range of pressures you can actually use, allowing you to more easily correct for the roughness of the surface.
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Tyre construction.
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Obviously the tyre construction has an effect on rolling resistance.
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By using less material, less material can and will be deformed.
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And the more flexible the material is, such as the rubber compound, the less energy is lost through deformation.
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Generally, smoother treads have a lower rolling resistance than rougher treads
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and that is why almost all road
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and triathlon racing tires have very smooth tread patterns
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if any tread pattern at all interestingly actually in racing tires for the road the tread pattern
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that is there is actually not there for grip
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or water dispersion it's mostly there for aerodynamics
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because the tread pattern actually trips the laminar flow as
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that of that air that's hitting the tire to improve the aerodynamics So,
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should you consult a website like BicycleRollingResistance.com where they list all the tested rolling resistance of all tyres
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and simply choose the one from the top of the list?
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Well, yes and no. Yes, the tires on the top of that list will be the fastest.
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However, they're always compromises.
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Some of them may sacrifice durability for that extra speed and be more prone to punctures.
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Some of them may have a different compound that sacrifices comfort
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and grip and road feel and some may simply not work well with your wheel and bike setup.
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It's also worth pointing out that the difference between the top of
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that list of racing tires and the middle of
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that list of racing tires is about a two to three watt saving
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which is an almost imperceptible difference for most mere mortals.
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They will however have a significant difference in those racing tires over your standard training tires.
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So the answer is that the best tire for you depends on many factors
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but it is worth considering investing the $100 to $200 in a good pair of racing tyres.
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It may just be the cheapest watts you buy this season.
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One more thing before we go, you may be asking which is faster rolling resistance-wise, tubeless or clincher?
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Well, the speed of a tyre actually depends on its construction and not whether it's set up clincher or tubeless.
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So, a slow tubeless tyre will actually be slower than a fast clincher tyre.
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However, generally speaking, setup does have better rolling resistance than a tube setup.
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However, if you put a latex tube in a clincher, the rolling resistance is actually the same as tubeless.
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I hope you've enjoyed this video.
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Happy riding!
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Лексика и советы по произношению к этому уроку
В этом видео 75 предложений и 1065 слов для шедоуинга. Речь длится 5:59. Говорящий говорит в естественном темпе, около 178 слов в минуту, близком к повседневной речи. Только 76% слов входят в 3000 самых частых слов английского языка, поэтому лексика сложная.
Ключевая лексика этого видео
15 слов из видео, которые стоит выучить, с произношением и значением:
| Слово | Произношение | Значение |
|---|---|---|
| tyre существительное | /taɪə(ɹ)/ | автомоби́льная ши́на, ши́на |
| tire глагол | /ˈtaɪ̯ɚ/ | устава́ть, уста́ть |
| tread глагол | /tɹɛd/ | топтать |
| smooth прилагательное | /smuːð/ | гла́дкий |
| upgrade глагол | /əpˈɡɹeɪd/ | модернизи́ровать, улучша́ть |
| inflation существительное | /ɪnˈfleɪ.ʃən/ | инфля́ция |
| narrow прилагательное | /ˈnæɹəʊ/ | у́зкий, те́сный |
| tube существительное | /tuːb/ | тю́бик |
| sacrifice существительное | /ˈsæk.ɹɪ.faɪs/ | жертвоприноше́ние |
| bearing существительное | /ˈbɛɹɪŋ/ | подши́пник |
| depend глагол | /dɪˈpɛnd/ | зави́сеть |
| patch существительное | /pæt͡ʃ/ | запла́та, запла́тка |
| compound существительное | /ˈkɑmpaʊnd/ | соедине́ние, сочета́ние |
| decrease глагол | /dɪˈkɹiːs/ | уменьша́ться, уме́ньшиться |
| grip существительное | /ˈɡɹɪp/ | захва́т, хва́тка |
Фразовые глаголы, которые вы услышите
| Слово | Произношение | Значение |
|---|---|---|
| hold back глагол | сде́рживать, сде́рживаться | |
| point out глагол | ука́зывать, указа́ть | |
| set up глагол | /ˌsɛt ˈʌp/ | устана́вливать, установи́ть |
Произношение, на которое стоит обратить внимание
- Звуки «th»: smooth /smuːð/, width /ˈwɪtθ/, triathlon /tɹaɪˈæθˌlɑn/
- Звуки «sh» и «zh»: inflation /ɪnˈfleɪ.ʃən/, essentially /ɪˈsɛnʃəli/, ratio /ˈɹeɪ.ʃoʊ/, tension /ˈtɛnʃən/, rotation /ɹoʊˈteɪʃən/
- Длинные слова — следите за ударением: essentially /ɪˈsɛnʃəli/, importantly /ɪmˈpɔɹ.tənt.li/, acceleration /əkˌsɛl.əˈɹeɪ.ʃən/, aerodynamic /ˌɛəɹəʊdaɪˈnæmɪk/, deformation /ˌdɛfəˈmeɪʃən/
Как заниматься с этим видео
- Прослушайте всё видео один раз молча и выпишите незнакомые слова.
- Начните со скорости 0,75×, повторяйте предложение за предложением и вернитесь к обычной скорости, когда станет легко.
- Запишите себя и сравните с оригиналом, обращая внимание на такие слова, как tyre, tire, tread.
Грамматика в этом видео
Конструкции, которые говорящий использует чаще всего, с точными словами из видео:
| Конструкция | В видео |
|---|---|
| Пассивный залог be + причастие прошедшего времени — важно, что происходит, а не кто это делает | is lost · is also expended · be overcome |
| Present Perfect have/has + причастие прошедшего времени — прошлое действие, важное сейчас | has already become · you've enjoyed |
Что такое техника Shadowing?
Shadowing — это научно обоснованная техника изучения языка, изначально разработанная для подготовки профессиональных переводчиков и популяризированная полиглотом доктором Александром Аргуэльесом. Метод прост, но эффективен: вы слушаете аудио на английском от носителей языка и немедленно повторяете вслух — как тень, следующая за говорящим с задержкой в 1–2 секунды. В отличие от пассивного прослушивания или грамматических упражнений, Shadowing заставляет мозг и мышцы рта одновременно обрабатывать и воспроизводить реальные речевые паттерны. Исследования показывают, что это значительно улучшает точность произношения, интонацию, ритм, связную речь, понимание на слух и беглость речи — что делает его одним из самых эффективных методов для подготовки к IELTS Speaking и реального общения на английском.