Maximum Human Torque II
10-18-23, 03:25 PM
#26
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Individuals have the right to choose a gear ratio that works for them, and there is no objective, absolute best ratio for a given hill. Some guys do better mashing a high gear at lower RPM, and others prefer to spin fast, with less force. As a rule of thumb, however, an RPM range of around 60 to 90 (maybe as high as 100) is the most efficient for an adult human. This is simply because of our physiology and muscle function. If the OP's son chooses to disregard this fact, he's putting himself at a disadvantage. The explanation for gear choice making a difference in hill climbing has to do with leverage. We get mechanical advantage from the bike's drivetrain, which makes it possible to turn the crank with a level of force and RPM rate that are efficient for our bodies.
It works the same way for other physical tasks. Say you want to move 100 lbs. of stuff from the floor to a table. It's possible for most of us to do it in one shot, but I'd prefer to make 3 to 5 trips of 20 to 33 lbs. each. Sure, it will require more movement, but my body has less of a problem with that than with lifting 100 lbs. I would not want to make 20 trips of 5 lbs. each, but nor would I want to do the full 100 at once.
It works the same way for other physical tasks. Say you want to move 100 lbs. of stuff from the floor to a table. It's possible for most of us to do it in one shot, but I'd prefer to make 3 to 5 trips of 20 to 33 lbs. each. Sure, it will require more movement, but my body has less of a problem with that than with lifting 100 lbs. I would not want to make 20 trips of 5 lbs. each, but nor would I want to do the full 100 at once.
Last edited by Broctoon; 10-18-23 at 03:30 PM.
10-18-23, 04:04 PM
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Seems to me that the best way to explain this subject is to drop the person like a hot rock. Unfortunately, this isn't always possible.
10-18-23, 05:45 PM
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I like the simplicity of this:
Would you rather pick up a 100-lb rock 10 times, or a 25-lb rock 40 times?
Would you rather pick up a 100-lb rock 10 times, or a 25-lb rock 40 times?
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10-18-23, 05:53 PM
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@Tribikenewbie
I never look at the display on the shifter but my Daughter liked to. it helped her visually understand what numbers to use
I never look at the display on the shifter but my Daughter liked to. it helped her visually understand what numbers to use
OP say that the bigger gears are harder to push and make you go faster, the little gears are easy to push but are slower. Your kid should figure out that he can’t go up the hill fast
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10-18-23, 06:06 PM
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I had a customer that didn't think about the double crankset in terms of high/low range, but instead easy/hard. Of course, "hard" meant going up "faster"...Only he couldn't understand why his whole drivertain was destroyed from continuous and excessive cross-chaining. The idea of high and low ranges with a substantial overlap was just too much for his brain to comprehend. Perhaps it is the same with your son?
Anyway. To illustrate a point, I prefer to suggest that climbing in too low of a cadence is a lot like doing leg-presses and then ask how many leg-presses does that person think a body builder does, & how long that person thinks a body builder can sustain doing so.
Generally speaking: Your cadence and your heart rate determine the mix of muscle fiber recruitment and where your body gets it's energy from. A lighter load at a higher cadence moves the metabolic load from the wasteful fast twitch muscle fibers generally towards the faster recovering more metabolically efficient slow twitch muscle fibers providing less waste for the cardiovascular system to deal with. With time and training, mitichondrial growth will help this efficiency even further. (and this is part of the reason for training volume at sustained intensity matters.)
Not unlike like shifting your car to an easier gear when climbing a mountain pass so that the increased speed of the water pump combined with less work being performed per engine revolution can avoid overheating your engine. At least, that's the visual in my head when I think about it.
All this is to say tate the speed at which your muscles are peak efficient and the speed they get the most work done are not the same. Doing the most work is what gets you up the hills fastest.
Anyway. To illustrate a point, I prefer to suggest that climbing in too low of a cadence is a lot like doing leg-presses and then ask how many leg-presses does that person think a body builder does, & how long that person thinks a body builder can sustain doing so.
Generally speaking: Your cadence and your heart rate determine the mix of muscle fiber recruitment and where your body gets it's energy from. A lighter load at a higher cadence moves the metabolic load from the wasteful fast twitch muscle fibers generally towards the faster recovering more metabolically efficient slow twitch muscle fibers providing less waste for the cardiovascular system to deal with. With time and training, mitichondrial growth will help this efficiency even further. (and this is part of the reason for training volume at sustained intensity matters.)
Not unlike like shifting your car to an easier gear when climbing a mountain pass so that the increased speed of the water pump combined with less work being performed per engine revolution can avoid overheating your engine. At least, that's the visual in my head when I think about it.
All this is to say tate the speed at which your muscles are peak efficient and the speed they get the most work done are not the same. Doing the most work is what gets you up the hills fastest.
Last edited by base2; 10-18-23 at 06:27 PM.
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10-18-23, 09:49 PM
#32
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Okay so you were on the right lines starting with Power = Torque x rpm
The rider applies an Input Torque (Pedal Force x Crank Length) and an Input rpm (Pedal Cadence). This gives Input Power as defined in the above general equation.
The drivetrain gears convert this rider Input Power into an Output Power at the rear wheel = Wheel Torque x Wheel rpm.
Apart from minor drivetrain losses (which we can ignore for this purpose) Input Power = Output Power and the gear ratio simply determines how the Output Torque and rpm are split. A lower gear provides a higher Output Torque and lower Wheel speed for a given Input Power level. So the rider has to apply less Crank Tiorque (lower Pedal Force) to get the same Wheel Torque (same driving force at the contact patch), but at the expense of a lower Wheel Speed (since Power is a constant).
That’s the best I can simplify it with the actual physics equations included. It may be confusing. A more simple explanation is that a lower gear ratio multiplies your torque input and divides your pedal rpm. So you get more torque at the rear wheel, but at a lower speed.
The rider applies an Input Torque (Pedal Force x Crank Length) and an Input rpm (Pedal Cadence). This gives Input Power as defined in the above general equation.
The drivetrain gears convert this rider Input Power into an Output Power at the rear wheel = Wheel Torque x Wheel rpm.
Apart from minor drivetrain losses (which we can ignore for this purpose) Input Power = Output Power and the gear ratio simply determines how the Output Torque and rpm are split. A lower gear provides a higher Output Torque and lower Wheel speed for a given Input Power level. So the rider has to apply less Crank Tiorque (lower Pedal Force) to get the same Wheel Torque (same driving force at the contact patch), but at the expense of a lower Wheel Speed (since Power is a constant).
That’s the best I can simplify it with the actual physics equations included. It may be confusing. A more simple explanation is that a lower gear ratio multiplies your torque input and divides your pedal rpm. So you get more torque at the rear wheel, but at a lower speed.
awesome!! Thank you PeteHski!
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10-18-23, 09:55 PM
#33
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Say you want to move 100 lbs. of stuff from the floor to a table. It's possible for most of us to do it in one shot, but I'd prefer to make 3 to 5 trips of 20 to 33 lbs. each. Sure, it will require more movement, but my body has less of a problem with that than with lifting 100 lbs. I would not want to make 20 trips of 5 lbs. each, but nor would I want to do the full 100 at once.
10-18-23, 10:16 PM
#34
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So on a related note (going for 5 time zombie!! It is almost Halloween), I’m trying to explain to “a friend” (who might be my son) the physics of why he should downshift the chainring (move to a smaller front gear) and back gear (move to a bigger cog) going up long, steep hills. The empirical evidence (practically coming to a stop and falling off the bike) is apparently not proof enough. I’m thinking the simple explanation is that he doesn’t have enough strength/can’t exert enough force to drive the largest front gear when the back gear is on a smaller cog - which would give apx 4 rotations of the back wheel for a single pedal/crank rotation. What are the physics to explain this? I saw a video where a body builder rode up a hill in high gear but his time was slower that an amateur biker (who used lower gears and more rotations) and he was dead tired vs the biker. I saw in this forum that Torque x rpm = power…. I assume more power is needed to go uphill than flat …but that’s as far as I can get…I can’t translate it into the gear explanation. Please help all you physics masters!!
Make sure you locate the bottom chord of a truss!
10-18-23, 11:41 PM
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With a taller gear you can go up the hill faster until you can't, then you slow immensely. If you try too hard, you can injure yourself.
Physics and physiology are both involved, but that's all you really need to know.
Physics and physiology are both involved, but that's all you really need to know.
10-19-23, 01:08 AM
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10-19-23, 01:10 AM
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yeah I also like the indicator, it’s what I grew up with and it’s the easiest way to keep from cross chaining. Wish road bikes didn’t move away from them. I used to know exactly what ratio I was in at all times (knew how many teeth were in my cogs) but I can’t do this on my road bikes.
OP say that the bigger gears are harder to push and make you go faster, the little gears are easy to push but are slower. Your kid should figure out that he can’t go up the hill fast
OP say that the bigger gears are harder to push and make you go faster, the little gears are easy to push but are slower. Your kid should figure out that he can’t go up the hill fast
BTW, there's an easy solution to your problem - look down.
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10-19-23, 03:32 PM
#40
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If you do the math, there is no torque difference between using different size sprockets front and back for the same overall ratio. The change in the distance of the front sprocket teeth from the crank center and the corresponding change in distance from the rear sprocket teeth from the center of the rear axle exactly offset one another so there is no torque change. There is an efficiency advantage to running a smaller sprocket up front and a smaller one out back as it keeps the chain friction lower.
10-19-23, 03:34 PM
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10-19-23, 03:39 PM
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If you do the math, there is no torque difference between using different size sprockets front and back for the same overall ratio. The change in the distance of the front sprocket teeth from the crank center and the corresponding change in distance from the rear sprocket teeth from the center of the rear axle exactly offset one another so there is no torque change. There is an efficiency advantage to running a smaller sprocket up front and a smaller one out back as it keeps the chain friction lower.
Some argue the more teeth solution is better because your chainrings/cassette cogs will last longer.
Not something I worry about though.
10-19-23, 03:52 PM
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10-19-23, 04:21 PM
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I think the opposite is true: a bigger ring up front, and a bigger cog in the back, is more efficient.
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10-19-23, 04:33 PM
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Here is an excerpt from his blog about “marginal gains”:
”It may sound like grasping at the smallest of marginal gains, but it is bigger than you likely thought. A 53x11 and 48x10 gear are more or less the same ratio of 126 gear inches. While it is the same gear, the 53x11 combination is 6w faster than its smaller 48x10 competitor. If you are looking to go faster for less energy it would be logical to have the absolute biggest chainrings and largest cassette options available to you. This also will help keep a better chain line which can improve efficiency as well! Save 6w by opting for the larger chain rings.
Otto
Last edited by ofajen; 10-19-23 at 04:38 PM.
10-19-23, 05:12 PM
#46
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Some old ex racers told me once they thought when riding on the track ,big-big was better for sustained efforts at low cadence like TTs, small-small for short efforts and high cadence.
10-19-23, 06:18 PM
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Correct. I think Jeff at Silca has measured this and shown that the energy loss per cog gets bigger, the smaller you go in the rear cog.
Here is an excerpt from his blog about “marginal gains”:
”It may sound like grasping at the smallest of marginal gains, but it is bigger than you likely thought. A 53x11 and 48x10 gear are more or less the same ratio of 126 gear inches. While it is the same gear, the 53x11 combination is 6w faster than its smaller 48x10 competitor. If you are looking to go faster for less energy it would be logical to have the absolute biggest chainrings and largest cassette options available to you. This also will help keep a better chain line which can improve efficiency as well! Save 6w by opting for the larger chain rings.
Otto
Here is an excerpt from his blog about “marginal gains”:
”It may sound like grasping at the smallest of marginal gains, but it is bigger than you likely thought. A 53x11 and 48x10 gear are more or less the same ratio of 126 gear inches. While it is the same gear, the 53x11 combination is 6w faster than its smaller 48x10 competitor. If you are looking to go faster for less energy it would be logical to have the absolute biggest chainrings and largest cassette options available to you. This also will help keep a better chain line which can improve efficiency as well! Save 6w by opting for the larger chain rings.
Otto
10-19-23, 06:25 PM
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10-19-23, 06:27 PM
#50
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