Weight and bike speed ratio
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2008-03-17 4:18 PM |
Pro 3673 MAC-opolis | Subject: Weight and bike speed ratio I read somewhere a long time ago that if you lose X pounds you gain X mph on the bike assuming power output is constant. Anyone know those ratios?
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2008-03-17 4:30 PM in reply to: #1276879 |
Resident Curmudgeon 25290 The Road Back | Subject: RE: Weight and bike speed ratio I would think it would depend in good measure on the course. Formula's going to be different on a 12% uphill than on a flat course or a 12% downhill, isn't it? Stop thinking and go ride. Oh yeah, drop some poundage while you're at it. You'll still be sexy (yeah, right) when you're little. |
2008-03-17 4:34 PM in reply to: #1276908 |
Pro 3673 MAC-opolis | Subject: RE: Weight and bike speed ratio the bear - 2008-03-17 5:30 PM I would think it would depend in good measure on the course. Formula's going to be different on a 12% uphill than on a flat course or a 12% downhill, isn't it? Stop thinking and go ride. Oh yeah, drop some poundage while you're at it. You'll still be sexy (yeah, right) when you're little. Why the "Resident Curmudgeon" tag? Oh wait....nevermind |
2008-03-17 4:38 PM in reply to: #1276879 |
over a barrier | Subject: RE: Weight and bike speed ratio Run http://www.runningforfitness.org/calc/weighteffect.php?metres=21100... You'll find everything you'll ever need here for cycling http://www.analyticcycling.com/ForcesPower_Page.html Edited by running2far 2008-03-17 4:46 PM |
2008-03-17 6:01 PM in reply to: #1276879 |
Master 1890 Cypress, CA | Subject: RE: Weight and bike speed ratio I think there are way too many variables that you have to assume are constant to get any sort of ratio based on weight vs. speed. For example, if you're assuming that the rider weight is reduced (presumably through exercise?), then it might not be reasonable to assume that power output would be constant, since you'd normally improve fitness in the process. You'd also have to assume same course, same environmental conditions, etc., etc. But I guess if you could do it and if you assumed that all weight counts, not just body weight, then you could figure out how much faster you'd be riding naked. That might be interesting... |
2008-03-17 8:07 PM in reply to: #1276879 |
Pro 4339 Husker Nation | Subject: RE: Weight and bike speed ratio All I know is that when I was out riding with two other guys who didn't weigh as much as I did I coasted down the hill faster! So that's gotta count for something They wanted to blame my bike, but I say it's force=mass x velocity. |
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2008-03-18 7:24 AM in reply to: #1276879 |
Master 2202 St. Louis | Subject: RE: Weight and bike speed ratio How bout you do a test... throw a 5lb weight in your backback... go ride.. check speed. Take weight out, go ride.. check speed. Report results. |
2008-03-18 8:56 AM in reply to: #1276879 |
Champion 6056 Menomonee Falls, WI | Subject: RE: Weight and bike speed ratio |
2008-03-18 10:50 AM in reply to: #1277330 |
Elite 3130 | Subject: RE: Weight and bike speed ratio Bripod - 2008-03-17 7:07 PM All I know is that when I was out riding with two other guys who didn't weigh as much as I did I coasted down the hill faster! So that's gotta count for something They wanted to blame my bike, but I say it's force=mass x velocity. close: your weight being higher produces more propulsive force during downhill travel (F=ma, a being due to gravity) and your aero drag being about the same as theirs means that you will see a higher coasting velocity than they will. There's even a non-dimensional measure called ballistic coefficient, which is essentially the ratio of weight to drag. Higher the ballistic coefficient, the faster the object goes before the drag force causes it to stop accelerating. |
2008-03-18 10:53 AM in reply to: #1276879 |
Elite 3130 | Subject: RE: Weight and bike speed ratio Big Sexy - 2008-03-17 3:18 PM I read somewhere a long time ago that if you lose X pounds you gain X mph on the bike assuming power output is constant. Anyone know those ratios?
mac - on the flats it's not gonna make that much difference because once you are up to speed most of the resistance is due to aero drag, which is not a function of mass. On uphills it makes a big big difference since you are now fighting gravity to pull the mass uphill. On downhills, the heavier object will have the speed advantage (all other things being equal). I think this is the big reason why in a bicycle stage race the "big guys" (relatively speaking) do well on the flattish sprint stages and the better climbers tend to be the "little guys." |
2008-03-18 11:00 AM in reply to: #1278132 |
Extreme Veteran 739 Westlake, OH | Subject: RE: Weight and bike speed ratio ScottoNM - 2008-03-18 11:53 AM On downhills, the heavier object will have the speed advantage (all other things being equal). Ok...this is what I can't get my little head around. Dropping a 1 pound weight and a 10 pound at the same time will cause them to hit the ground at the same time. Why doesn't his apply to bikes going down hill? What is different between the two? Edited by ohiost90 2008-03-18 11:01 AM |
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2008-03-18 11:01 AM in reply to: #1278121 |
Pro 4339 Husker Nation | Subject: RE: Weight and bike speed ratio ScottoNM - 2008-03-18 10:50 AM Bripod - 2008-03-17 7:07 PM All I know is that when I was out riding with two other guys who didn't weigh as much as I did I coasted down the hill faster! So that's gotta count for something They wanted to blame my bike, but I say it's force=mass x velocity. close: your weight being higher produces more propulsive force during downhill travel (F=ma, a being due to gravity) and your aero drag being about the same as theirs means that you will see a higher coasting velocity than they will. There's even a non-dimensional measure called ballistic coefficient, which is essentially the ratio of weight to drag. Higher the ballistic coefficient, the faster the object goes before the drag force causes it to stop accelerating. Well there you have it! One of the other guys was actually taller than I am, yet he weighed the second most and coasted the second fastest. The third guy was shorter and weighed less than both of us and was slowest. It was very interesting to observe. |
2008-03-18 11:21 AM in reply to: #1278145 |
Not a Coach 11473 Media, PA | Subject: RE: Weight and bike speed ratio ohiost90 - 2008-03-18 11:00 AM ScottoNM - 2008-03-18 11:53 AM On downhills, the heavier object will have the speed advantage (all other things being equal). Ok...this is what I can't get my little head around. Dropping a 1 pound weight and a 10 pound at the same time will cause them to hit the ground at the same time. Why doesn't his apply to bikes going down hill? What is different between the two?
Your example is true in a vacuum. Outside the vacuum, air resistance comes into play. All other things equal, the heavier object will be able to better overcome air resistance and reach a higher terminal velocity. (I think.) |
2008-03-18 1:03 PM in reply to: #1278191 |
Champion 10154 Alabama | Subject: RE: Weight and bike speed ratio JohnnyKay - 2008-03-18 11:21 AM ohiost90 - 2008-03-18 11:00 AM ScottoNM - 2008-03-18 11:53 AM On downhills, the heavier object will have the speed advantage (all other things being equal). Ok...this is what I can't get my little head around. Dropping a 1 pound weight and a 10 pound at the same time will cause them to hit the ground at the same time. Why doesn't his apply to bikes going down hill? What is different between the two?
Your example is true in a vacuum. Outside the vacuum, air resistance comes into play. All other things equal, the heavier object will be able to better overcome air resistance and reach a higher terminal velocity. (I think.)
Whenever I ride in group rides and races I pass people left and right going downhill and then they pass me right back as we head back up the next climb. In Louisiville last year I played leap-frog with another rider like 12 times on the rolling hills. I'd pass her on the down and she pass me back on the up. It's not a zero-sum-game though as it's simply takes more energy to move a bigger mass over a given distance. Sunday I biked 50 miles and averaged 16.47 mph. I'm 265 lbs. If I would drop 50 lbs, I could probably average 29 mph! OK, probably not....but I'd be much faster for sure. ~Mike |
2008-03-18 2:34 PM in reply to: #1278191 |
Elite 3130 | Subject: RE: Weight and bike speed ratio JohnnyKay - 2008-03-18 10:21 AM ohiost90 - 2008-03-18 11:00 AM ScottoNM - 2008-03-18 11:53 AM On downhills, the heavier object will have the speed advantage (all other things being equal). Ok...this is what I can't get my little head around. Dropping a 1 pound weight and a 10 pound at the same time will cause them to hit the ground at the same time. Why doesn't his apply to bikes going down hill? What is different between the two?
Your example is true in a vacuum. Outside the vacuum, air resistance comes into play. All other things equal, the heavier object will be able to better overcome air resistance and reach a higher terminal velocity. (I think.) yup, well said Johnny
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2008-03-18 2:38 PM in reply to: #1276879 |
Pro 4339 Husker Nation | Subject: RE: Weight and bike speed ratio So basically what we've learned here is that if you're doing a race that goes downhill more than it goes uphill then you'll do well to be heavier. If you've got more climbs than descents, it's time to shed a few pounds. Or, a third option would be to gain a BUNCH of weight before the descent, then lose it all on the ascent. This might require some engineering. |
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2008-03-18 2:51 PM in reply to: #1278759 |
Resident Curmudgeon 25290 The Road Back | Subject: RE: Weight and bike speed ratio Bripod - 2008-03-18 2:38 PM So basically what we've learned here is that if you're doing a race that goes downhill more than it goes uphill then you'll do well to be heavier. Not at all. It would have to have a lot more descents for you to spend more time going downhill than up, which is the only way being heavier would be an advantage. |
2008-03-18 2:56 PM in reply to: #1278790 |
Champion 10154 Alabama | Subject: RE: Weight and bike speed ratio the bear - 2008-03-18 2:51 PM Bripod - 2008-03-18 2:38 PM So basically what we've learned here is that if you're doing a race that goes downhill more than it goes uphill then you'll do well to be heavier. Not at all. It would have to have a lot more descents for you to spend more time going downhill than up, which is the only way being heavier would be an advantage.
I rode in Denali National Park one time and we biked uphill for about a mile and then rode downhill the next 15 miles. It was awesome! Not a race of course, but a really fun ride. ~Mike |
2008-03-18 3:00 PM in reply to: #1278810 |
Resident Curmudgeon 25290 The Road Back | Subject: RE: Weight and bike speed ratio Rogillio - 2008-03-18 2:56 PM the bear - 2008-03-18 2:51 PM Bripod - 2008-03-18 2:38 PM So basically what we've learned here is that if you're doing a race that goes downhill more than it goes uphill then you'll do well to be heavier. Not at all. It would have to have a lot more descents for you to spend more time going downhill than up, which is the only way being heavier would be an advantage.
I rode in Denali National Park one time and we biked uphill for about a mile and then rode downhill the next 15 miles. It was awesome! Not a race of course, but a really fun ride. ~Mike I've often thought in Tahoe that they should run the ski lifts in the summer for bicycles, especially coming down off of Spooner Junction going south. |
2008-03-18 3:08 PM in reply to: #1276879 |
Extreme Veteran 510 Falls Church, VA | Subject: RE: Weight and bike speed ratio When you climb a hill you're increasing your potential energy, mass times vertical dist travelled. The heavier you are the more potential energy you have in the bank. Once you're pointed down the heavier rider now has a bigger energy bank account to spend on overcoming the air resistance on the descent. |
2008-03-18 3:09 PM in reply to: #1278790 |
Pro 4339 Husker Nation | Subject: RE: Weight and bike speed ratio the bear - 2008-03-18 2:51 PM Bripod - 2008-03-18 2:38 PM So basically what we've learned here is that if you're doing a race that goes downhill more than it goes uphill then you'll do well to be heavier. Not at all. It would have to have a lot more descents for you to spend more time going downhill than up, which is the only way being heavier would be an advantage. Sheesh Bear, I set it up on a tee for you and you completely whiff. Your canned response would be "You forgot option #4 which supersedes all other methods you mentioned, which is ride lots." and then you do your sunglasses smiley thing. |
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2008-03-18 5:54 PM in reply to: #1278857 |
Elite 3130 | Subject: RE: Weight and bike speed ratio Bripod - 2008-03-18 2:09 PM the bear - 2008-03-18 2:51 PM Sheesh Bear, I set it up on a tee for you and you completely whiff. Your canned response would be "You forgot option #4 which supersedes all other methods you mentioned, which is ride lots." and then you do your sunglasses smiley thing.Bripod - 2008-03-18 2:38 PM So basically what we've learned here is that if you're doing a race that goes downhill more than it goes uphill then you'll do well to be heavier. Not at all. It would have to have a lot more descents for you to spend more time going downhill than up, which is the only way being heavier would be an advantage.
but if I ride lots then I will lose weight and, thus, my downhill speed advantage
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2008-03-18 6:06 PM in reply to: #1276879 |
Champion 6993 Chicago, Illinois | Subject: RE: Weight and bike speed ratio There is an old question which will help you more, losing 3 lbs off you or lbs off the bike? The anwser is off you since the bike tends to have the same areo drag but you will have less. Look at before and after photos and you will see how wide a person was and how much more aerodyanic they are. on the tri-talk blog I think they figured 3 lbs would save you 21 secs over an Oly vs 7 secs with a 3lb lose on the bike. Moral of the story just do your best to be as lean as you can be. It will help you out in your biking espically up hills and will be huge on the run. |
2008-03-18 10:32 PM in reply to: #1276879 |
Extreme Veteran 498 Carpinteria, Ca. | Subject: RE: Weight and bike speed ratio I wear one of those pregnancy training bellys for my long rides, that way I get to train heavy and race light. I actually do take three full large water bottles on every ride I do to add to my weight for climbing, hopefully it helps come race time, we shall see. Edited by ZekeB 2008-03-18 10:33 PM |
2008-03-19 12:53 PM in reply to: #1276879 |
Pro 3673 MAC-opolis | Subject: RE: Weight and bike speed ratio |
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