Coasting down hill
#101
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Last edited by njkayaker; 05-29-22 at 07:34 AM.
#102
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on edit: yep, you stated the same while I was (slowly) typing, so we’re all good!
on edit again: okay, now you deleted all that. I can’t keep up…
Last edited by tomato coupe; 05-29-22 at 07:34 AM.
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The first two links are good, because they’re about quadratic functions, not the quadratic equation, which was your earlier link. But, this is just semantics now. PeteHski’s original objection to my use of the term quadratic was because of the absence of the linear term in aerodynamic drag. We all agree that the term is not required in a quadratic function; we’ve just stated it differently.
on edit: yep, you stated the same while I was (slowly) typing, so we’re all good!
on edit: yep, you stated the same while I was (slowly) typing, so we’re all good!
His mistake was thinking the coefficients had to be nonzero.
(The quadratic equation is about finding roots of quadratic functions.)
Last edited by njkayaker; 05-29-22 at 07:45 AM.
#104
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its funny, im huge but due to a neck injury am not aerodynamic at all. At high speeds I struggle, smaller riders with a more aggressive position pull ahead. For instance going down Alpine, the fast groups are going over 30 mph and ive been dropped thinking I would just ride away from the field because I have an extra 100 lbs on the average rider. Aerodynamics are so huge at high speeds, I find that even though im 260 lbs I'm strongest on false flats and headwinds where power is king. I think the benefit of weight is overstated on descents unless the rider is flexible and aero.
#105
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Yeah, that's what threw me a little. But anyway we all agree aero drag is directly proportional to speed squared and it is a very simple quadratic function.
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#106
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its funny, im huge but due to a neck injury am not aerodynamic at all. At high speeds I struggle, smaller riders with a more aggressive position pull ahead. For instance going down Alpine, the fast groups are going over 30 mph and ive been dropped thinking I would just ride away from the field because I have an extra 100 lbs on the average rider. Aerodynamics are so huge at high speeds, I find that even though im 260 lbs I'm strongest on false flats and headwinds where power is king. I think the benefit of weight is overstated on descents unless the rider is flexible and aero.
Years ago, I was riding with a smallish woman. She as not only no more than 5'3", she was also thin, so MAYBE 110lbs soaking wet. I'd just pulled us along Portola, so when we hit Alpine, she took the lead, and was pedaling away for dear life, while I was coasting, and having to brake a lot so as not to roll over her. After about 30 seconds of this, I pulled around her and said, "Here, let me..." and pulled all the way to Santa Cruz Avenue, at a speed she'd never have managed on her own.. I let her pull us along the Alameda, since that's flat/rolling.
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#107
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You'll never ride away from them with a 42x18. They're rocking 52 or 53 x 11. At 30 mph you'd be thrashing away at 160 rpm, bouncing all over the place and wasting tons of energy. You're leaving a ginormous hole in the air. They can tuck into that and roll along at a nice, easy 80 rpm - barely ticking over. If they spin up to 90 rpm, they're going almost 35 mph, and you're OTB and flailing like mad, unable to catch up. Weight gives you some advantage, but you're giving up all that advantage and more by sitting up and by trying to push a 42x18.
Years ago, I was riding with a smallish woman. She as not only no more than 5'3", she was also thin, so MAYBE 110lbs soaking wet. I'd just pulled us along Portola, so when we hit Alpine, she took the lead, and was pedaling away for dear life, while I was coasting, and having to brake a lot so as not to roll over her. After about 30 seconds of this, I pulled around her and said, "Here, let me..." and pulled all the way to Santa Cruz Avenue, at a speed she'd never have managed on her own.. I let her pull us along the Alameda, since that's flat/rolling.
Years ago, I was riding with a smallish woman. She as not only no more than 5'3", she was also thin, so MAYBE 110lbs soaking wet. I'd just pulled us along Portola, so when we hit Alpine, she took the lead, and was pedaling away for dear life, while I was coasting, and having to brake a lot so as not to roll over her. After about 30 seconds of this, I pulled around her and said, "Here, let me..." and pulled all the way to Santa Cruz Avenue, at a speed she'd never have managed on her own.. I let her pull us along the Alameda, since that's flat/rolling.
#108
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I ride a route with 3000 feet of climbing over 22 miles that's about 90% climbing, so on the descent, there's an equal amount of descending. The steepest grade is only about 6%, but with some tail wind I can sometimes spin up to around 120 rpm and 44 mph with my 48/10 top gear that's the same as a traditional 53/11. I coast briefly if the grade takes me into the mid to upper 30's. Except for the steepest grades, I'm pedaling at 90-100 rpm and only applying a modest torque which is soft pedaling. My heart rate stays well under 150 bpm, so I'm not working very hard on this very long descent, but I'm going significanty faster than I would by coasting. After 22 miles of climbing, I want some easier riding on the way down.
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Alpine is about a -2% gradient. For you, at 260, essentially riding on the tops, going 30 mph would take almost 400w. A 160 lb rider in the drops would require a little over 400 w. BUT, if you're ahead of them, they might only have to put out 70% of that, which is only 280w. So, you're putting out power you probably can't manage for more than a couple minutes, max, while if they're sitting in the big hole you punch through the air, they're putting out power they might be able to manage for an hour or more. If you watch attacks in pro cycling, or even amateur stuff, almost nobody attacks from the front. The riders behind just accelerate to get back into the slipstream and they're ALWAYS doing less work. Attacks can work if you pass the guys in front already going A LOT faster than they are. So, you MIGHT drop them if you 1) start from the back of the pack, 2) pass the front of the group doing 30+ when they're going 25, and 3) are in the drops. That 400w that only gets you 30 mph when you're sitting up will get you 35 mph in the drops.
But, you know, if you're already running on the edge of the red just sticking with them, you'll never drop them. They're that much stronger.
EDIT: Credit for my understanding of this comes from watching the NorCal Cycling channel on YouTube. He does a really good job of explaining this stuff, using his own and others race footage. And the videos are fun to watch!
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#110
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I played around a little on Bikecalculator.com. Unfortunately, although it takes rider weight as a parameter, it doesn't have rider height.
Alpine is about a -2% gradient. For you, at 260, essentially riding on the tops, going 30 mph would take almost 400w. A 160 lb rider in the drops would require a little over 400 w. BUT, if you're ahead of them, they might only have to put out 70% of that, which is only 280w. So, you're putting out power you probably can't manage for more than a couple minutes, max, while if they're sitting in the big hole you punch through the air, they're putting out power they might be able to manage for an hour or more. If you watch attacks in pro cycling, or even amateur stuff, almost nobody attacks from the front. The riders behind just accelerate to get back into the slipstream and they're ALWAYS doing less work. Attacks can work if you pass the guys in front already going A LOT faster than they are. So, you MIGHT drop them if you 1) start from the back of the pack, 2) pass the front of the group doing 30+ when they're going 25, and 3) are in the drops. That 400w that only gets you 30 mph when you're sitting up will get you 35 mph in the drops.
But, you know, if you're already running on the edge of the red just sticking with them, you'll never drop them. They're that much stronger.
EDIT: Credit for my understanding of this comes from watching the NorCal Cycling channel on YouTube. He does a really good job of explaining this stuff, using his own and others race footage. And the videos are fun to watch!
Alpine is about a -2% gradient. For you, at 260, essentially riding on the tops, going 30 mph would take almost 400w. A 160 lb rider in the drops would require a little over 400 w. BUT, if you're ahead of them, they might only have to put out 70% of that, which is only 280w. So, you're putting out power you probably can't manage for more than a couple minutes, max, while if they're sitting in the big hole you punch through the air, they're putting out power they might be able to manage for an hour or more. If you watch attacks in pro cycling, or even amateur stuff, almost nobody attacks from the front. The riders behind just accelerate to get back into the slipstream and they're ALWAYS doing less work. Attacks can work if you pass the guys in front already going A LOT faster than they are. So, you MIGHT drop them if you 1) start from the back of the pack, 2) pass the front of the group doing 30+ when they're going 25, and 3) are in the drops. That 400w that only gets you 30 mph when you're sitting up will get you 35 mph in the drops.
But, you know, if you're already running on the edge of the red just sticking with them, you'll never drop them. They're that much stronger.
EDIT: Credit for my understanding of this comes from watching the NorCal Cycling channel on YouTube. He does a really good job of explaining this stuff, using his own and others race footage. And the videos are fun to watch!
#111
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Well its only on the slow days that I am strong enough to attack, and its rare for someone to follow. They just watch me blow myself up off the front for a few minutes max until im caught by the wednesday social ride and then often am gassed and dropped altogether.
#114
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On my regular 22 mile descent yesterday, a group of 5 young and serious looking riders passed me quickly, so I latched on, staying 4-6 feet behind the last rider. I had no problem keeping up with this group who were all probably 40 years younger. You don't need to stay very close to benefit from the draft. I even managed to stay in contact along a short stretch where the slope went up.
#115
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On my regular 22 mile descent yesterday, a group of 5 young and serious looking riders passed me quickly, so I latched on, staying 4-6 feet behind the last rider. I had no problem keeping up with this group who were all probably 40 years younger. You don't need to stay very close to benefit from the draft. I even managed to stay in contact along a short stretch where the slope went up.