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Bumps and efficiency
Do bumpy road surfaces typically exact costs in riding efficiency?
While doing a loop that I've ridden dozens of times, I noticed that my speed had dropped almost two MPH from my norm on a section that had recently been chip sealed (as opposed to the baby's butt smooth pavement that existed previously). I didn't feel especially cooked (at least, no more than usual), there didn't seem to be any wind, and I was able to ramp the speed back up to normal after turning off the choppy surface, all of which led me to question whether it was indeed the bumpiness that was affecting me. Does anyone have any similar anecdotes? Any studies of this? Was I dreaming? I'm curious if it is more beneficial in a long ride/race where crappy roads are the norm to use 25mm tires vs. 23s. TIA, SYJ |
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#2
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Bumps and efficiency
Yes, most definitely. For the same reason that knobby tires are less
efficient than smooth ones (on pavement, anyways). On a bumpy road, part of your energy output is used to overcome the bumps, leain less for propelling you forwards. Therefore you have to put out more energy to accomplish the same amount of horizontal movement. - - Comments and opinions compliments of, "Your Friendly Neighborhood Wheelman" My web Site: http://geocities.com/czcorner To E-mail me: ChrisZCorner "at" webtv "dot" net |
#3
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Bumps and efficiency
On 29 Jun 2006 12:02:23 -0700, "SYJ" wrote:
Do bumpy road surfaces typically exact costs in riding efficiency? While doing a loop that I've ridden dozens of times, I noticed that my speed had dropped almost two MPH from my norm on a section that had recently been chip sealed (as opposed to the baby's butt smooth pavement that existed previously). I didn't feel especially cooked (at least, no more than usual), there didn't seem to be any wind, and I was able to ramp the speed back up to normal after turning off the choppy surface, all of which led me to question whether it was indeed the bumpiness that was affecting me. Does anyone have any similar anecdotes? Any studies of this? Was I dreaming? I'm curious if it is more beneficial in a long ride/race where crappy roads are the norm to use 25mm tires vs. 23s. TIA, SYJ Dear SYJ, Yes, rougher surfaces slow tires down. Coefficient of Rolling Resistance Wooden Track 0.001 Smooth Concrete 0.002 Asphalt Road 0.004 Rough but Paved Road 0.008 http://www.analyticcycling.com/ForcesSpeed_Page.html If you plug those values into the calculator and use the defaults, you get speeds of 7.79, 7.68, 7.46, and 7.04 m/s, or 17.43, 17.18, 16.69, and 15.75 mph. The effect of chip seal is quite noticeable. My daily downhill speed improved nicely years ago after the wretched chip seal was paved. Cheers, Carl Fogel |
#4
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Bumps and efficiencyP.S.
If you regularly ride a good portion of chip & tar (or as I like to call
it "40 grit") pavement I would seriously consider tires no less than 25mm wide. Here in the Carolina Piedmont, where most secondary roads are of this type, you almost never see anything narrower than 25mm, even on the top level road racing machines. - - Comments and opinions compliments of, "Your Friendly Neighborhood Wheelman" My web Site: http://geocities.com/czcorner To E-mail me: ChrisZCorner "at" webtv "dot" net |
#5
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Bumps and efficiency
On 29 Jun 2006 12:02:23 -0700, "SYJ" wrote:
Do bumpy road surfaces typically exact costs in riding efficiency? Yes, particularly if the bike has high-pressure tires and lacks suspension. While doing a loop that I've ridden dozens of times, I noticed that my speed had dropped almost two MPH from my norm on a section that had recently been chip sealed (as opposed to the baby's butt smooth pavement that existed previously). I didn't feel especially cooked (at least, no more than usual), there didn't seem to be any wind, and I was able to ramp the speed back up to normal after turning off the choppy surface, all of which led me to question whether it was indeed the bumpiness that was affecting me. It was the road. There may have been an additional penalty from the stickiness of the surface if the sealer was leaking through to the top of the gravel layer, but a good tar-and-gravel application won't put any tar on the top. Does anyone have any similar anecdotes? Any studies of this? Was I dreaming? I'm curious if it is more beneficial in a long ride/race where crappy roads are the norm to use 25mm tires vs. 23s. 2mm of tire won't help IMO. 15mm might, but I would expect the gain to be small if any. I can't offer any figures to support that assertion; it's just an opinion based on limited experience. I know that swapping from a knobby to a smooth tire of the same size had a benefit similar to what you saw in the case of the smooth vs gravel-encrusted surface. Wider tires may produce increased rolling resistance relative to a narrower one (partially due to running at a lower pressure), and they add to the frontal profile (and thereby to drag) somewhat as well. -- Typoes are a feature, not a bug. Some gardening required to reply via email. Words processed in a facility that contains nuts. |
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Bumps and efficiencyP.S.
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#7
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Bumps and efficiency
SYJ wrote:
Do bumpy road surfaces typically exact costs in riding efficiency? While doing a loop that I've ridden dozens of times, I noticed that my speed had dropped almost two MPH from my norm on a section that had recently been chip sealed (as opposed to the baby's butt smooth pavement that existed previously). I didn't feel especially cooked (at least, no more than usual), there didn't seem to be any wind, and I was able to ramp the speed back up to normal after turning off the choppy surface, all of which led me to question whether it was indeed the bumpiness that was affecting me. Does anyone have any similar anecdotes? Yes. Around here road maintenance is by county. At many places one can cross a county line and go from chip seal to smooth pavement or vice-versa. Transitioning to smooth pavement is more than enough to shift up a gear, despite no change in grade or wind direction. Mark |
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Bumps and efficiencyP.S.
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#9
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Bumps and efficiencyP.S.
Chris Z The Wheelman wrote: ---snip--- If you regularly ride a good portion of chip & tar (or as I like to call it "40 grit") pavement I would seriously consider tires no less than 25mm wide. ---/snip--- Is this due to the perception of increased comfort, or because there is an increase in efficiency (decrease in rolling resistance) due to the fatter tires? SYJ |
#10
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Bumps and efficiency
Mark Logan writes:
Do bumpy road surfaces typically exact costs in riding efficiency? While doing a loop that I've ridden dozens of times, I noticed that my speed had dropped almost two MPH from my norm on a section that had recently been chip sealed (as opposed to the baby's butt smooth pavement that existed previously). I didn't feel especially cooked (at least, no more than usual), there didn't seem to be any wind, and I was able to ramp the speed back up to normal after turning off the choppy surface, all of which led me to question whether it was indeed the bumpiness that was affecting me. Does anyone have any similar anecdotes? Any studies of this? Was I dreaming? I'm curious if it is more beneficial in a long ride/race where crappy roads are the norm to use 25mm tires vs. 23s. As everyone else has said, yes, bumpy roads make you go slower. The book "Bicycling Science" (Wilson, MIT Press) cites a study that looked at the relationship of energy loss to bump frequency (i.e. speed divided by peak-to-peak distance of the bumps). One interesting finding of the study was that energy loss was proportional to the level of discomfort reported by the rider. So the more it hurts, the more its slowing you down. I think this subject got off on the wrong foot, the term "bumps" and road surface being ill defined. Chip-seal is surface roughness that flexes tire tread and causes rubber losses. A bumpy road with smooth surface makes pedaling and sitting difficult. Both have an effect on speed. Effect of chip seal is easily seen if one rider coasts down the shoulder of the road that wasn't chip-sealed while another coasts on the rough surface. Switching back and forth shows a noticeable relative difference in speed. As for bumpy roads with, for instance many smooth patches and dips and lumps, is harder to find for such a test, such roads generally not being straight enough and constant in slope to do a coasting test. I don't believe a chip-seal can take off 2mph through rubber losses but it can be uncomfortable enough to slow a rider that much together with the rolling resistance. Jobst Brandt |
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