I get that low gears > more power but low speed. I get that high gears >low power but high speed.
But can someone give me the brain dead intuition of why you need to change gear “sizes”? A single sentence if possible.
I’ve tried Googling it but they always use a bike example. I’ve never ridden a bike. Or they start talking about ratios and it just goes over my head.
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Here’s a different way to think of it: Your engine and wheels need different things. Gears let them both be happy.
Your tires are about two feet wide, so they’re about six feet around, and they turn once every six feet you drive. That means they turn about 900 times per mile, no matter how fast or slow you go. At 450 rotations per minute of the wheel, you’re going 30 mph. At 900 rotations per minute, you’re going 60 mph, a mile a minute. At 1800 rpm, you’d be going 120 mph.
Your engine, on the other hand, idles at about 600 rpm, and is healthiest around 2500-3000 rpm at highway speeds. It can’t really go slower than 600 rpm. Without gears, your minimum speed would be 600 wheel turns per minute, which about 45 miles per hour!
So, at low speeds, you may need to be able to spin your engine 5-10 times for each wheel turn. At higher speeds, that number shrinks, because the engine turn number and the wheel turn number are closer to each other.
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