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legos, may explain low rpm vs high rpm in cyclist
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well at least the decades old car debate well explained.


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Re: legos, may explain low rpm vs high rpm in cyclist [synthetic] [ In reply to ]
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This perfectly explains why I am slow. I have a sports car engine turning over at the rate of the truck engine.
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Re: legos, may explain low rpm vs high rpm in cyclist [musttriharder] [ In reply to ]
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musttriharder wrote:
This perfectly explains why I am slow. I have a sports car engine turning over at the rate of the truck engine.
Impressive. I don't think I've ever exceeded a cadence of about 170rpm, and for anything more than a few minutes I prefer the 70-90rpm range.
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Re: legos, may explain low rpm vs high rpm in cyclist [synthetic] [ In reply to ]
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With this logic you would expect taller/bigger riders to have lower RPM and smaller riders to have higher RPM right? I don't think there is any evidence of that correlation being true? None the less at least i learned something today.
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Re: legos, may explain low rpm vs high rpm in cyclist [lassekk] [ In reply to ]
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6-6.5 here, and it's virtually impossible for me to finish a Zwift ride not at 80rpm average. Anything over 100 feels like my legs are going to fall off.

I wrote this, you should read it:
https://www.slowtwitch.com/...n_Swimming_6700.html
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Re: legos, may explain low rpm vs high rpm in cyclist [lassekk] [ In reply to ]
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N=1 - I'm 1.91m and 90-100kg and all my rides are mid to low 70's for rpm.
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Re: legos, may explain low rpm vs high rpm in cyclist [synthetic] [ In reply to ]
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synthetic wrote:
well at least the decades old car debate well explained.

Power is work over time.
Torque is force at a distance.

If I had to guess what works better for one person or another it's going to be what muscle fibers their body naturally has more of combined with the training they do that then encourages the body to develop certain fibers more than others. Nature combined with nurture.

I find it interesting that Google tells me rec runners typically average 160 spm. And more elites can average 180 and sometimes a hair more.

I also find it interesting if you halve that and apply the generality of "rec" and "competitive" from that to a bike by dividing by 2 to get cadence..........you get 75 or 80rpm and then 90 or 95rpm.

I think there's a lot of "nature" there driving bike cadence from running motion.

Even the effort levels and cadences kind of align. You run faster paces you typically increase your run cadence. Same on the bike. Applied from a jog to a 5k pace to a sprint.........increasing cadence. Bike......from a Z1 lope, to a Z4 threshold effort, to an all out track sprint.........increasing cadence.

I don't think it's a bike thing, I think it is a human running thing that the body translates over to the bike.
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Re: legos, may explain low rpm vs high rpm in cyclist [lassekk] [ In reply to ]
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lassekk wrote:
With this logic you would expect taller/bigger riders to have lower RPM and smaller riders to have higher RPM right? I don't think there is any evidence of that correlation being true? None the less at least i learned something today.
As a general rule, kinda. However, you're trying to extrapolate that to a question around interaction between human bodies and bicycles where a significant number of parameters don't scale conveniently. So, I don't think that's a wise rabbit hole to go down as a follow on from an introductory explanation of some very basic physics concepts. The video is just an attempt to explain two basic terms to those not of a technical background. If you weren't clear on the difference between power and torque, then hopefully it helped (it's not entirely accurate but a reasonable effort at an explainer), but using the car and HGV comparison as an analogy to small and large people is flawed.
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Re: legos, may explain low rpm vs high rpm in cyclist [synthetic] [ In reply to ]
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6:20- When we're in a car and the car accelerates, we are feeling the force of the car pushing us against the seat
---

I think he picked a bad example there. The force we 'feel' is not the same as the force that actually happens in this situation. We feel like we're being pushed backwards due to inertia, which is not a force. The force that exists is the normal force, which is actually pushing us forward, of the car seat due to the acceleration of the car.






Take a short break from ST and read my blog:
http://tri-banter.blogspot.com/
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Re: legos, may explain low rpm vs high rpm in cyclist [synthetic] [ In reply to ]
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I think that it is remiss to say that it explains completely the high vs low RPM in cyclists, however the influence of weight no doubt plays a part alongside leg length, specific muscle size/strength, position on the bike and crank length.

I'm 63kg (afraid you'll have to do the math's to convert that to freedom units) and 182cm, with my legs definitely longer than average for my height. I average 85-95 rpm as my natural cadence with both 172.5 and 165mm cranks. My cadence is definitely higher when my saddle position is further forward as well.
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Re: legos, may explain low rpm vs high rpm in cyclist [synthetic] [ In reply to ]
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This is cool. The concepts of torque and power are some of the most difficult concepts to explain to people. It is a lot like the challenge of explaining current and voltage. Folks who live in those disciplines have an inherent understanding, but most of them are completely unable to explain it to a layperson. Ironically, riding a bike while watching speed and power is one of the greatest ways that a layperson can see and understand how the two are related.

The issue of torque and power has been a regular topic in car magazines over the years. I have probably read more than a dozen similar articles in Car and Driver, Motor Trend, Auto Trend, and Road and Track over the years that fall short with their readers. They should just send Legos to their readers instead.
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Re: legos, may explain low rpm vs high rpm in cyclist [lassekk] [ In reply to ]
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lassekk wrote:
With this logic you would expect taller/bigger riders to have lower RPM and smaller riders to have higher RPM right? I don't think there is any evidence of that correlation being true? None the less at least i learned something today.

Internal combustion engines are limited in RPM by structural stresses. The stresses in engines, which mostly share relatively common design aspects, are defined by and scale with the mean piston speed. Engines of similar design will have roughly the same stresses at the same mean piston speed, even if one engine is dramatically larger than the other. But because a piston in a large engine has to travel further for every rotation of the crank shaft, the rpm to achieve the same mean piston speed is lower in the larger engine.

Because cyclists really don't come anywhere close to their structural limits at even high pedalling rpms, we do not have this limitation (we are limited by other things). If we assume that a larger rider uses a longer crank, then the larger rider WILL have to move their foot at a higher angular velocity than the smaller rider on the shorter crank, but not so much that they are going to be tearing muscles or breaking bones.

If the riders use the same length crank, then their angular velocity is the same.

-------------
Ed O'Malley
www.VeloVetta.com
Founder of VeloVetta Cycling Shoes
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Re: legos, may explain low rpm vs high rpm in cyclist [ In reply to ]
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Part 2: The other thing that makes these concepts insanely difficult for most people is the confusion between mass and force. In the English System, we use lbs. for both. In the Metric System, no one knows what a Newton is and probably have not heard the term before.

Edit: And, yet another layer of the jacked-up-ness is that "foot-pound" (work) is not the same as "pound-foot" (torque) in the English system. And, this is expressed backwards on most torque gauges and inconsistent from how the metric system expresses torque (force-distance).
Last edited by: exxxviii: May 7, 21 8:27
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Re: legos, may explain low rpm vs high rpm in cyclist [lassekk] [ In reply to ]
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lassekk wrote:
With this logic you would expect taller/bigger riders to have lower RPM and smaller riders to have higher RPM right? I don't think there is any evidence of that correlation being true? None the less at least i learned something today.

not sure it works like that, as I am 9" taller than my wife yet we have the same leg length. so maybe instead of 175 cranks I should be using smaller? (she has 165). This also probably comes into play into hill climbs where you stand and mash vs sit and spin
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Re: legos, may explain low rpm vs high rpm in cyclist [exxxviii] [ In reply to ]
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exxxviii wrote:
Part 2: The other thing that makes these concepts insanely difficult for most people is the confusion between mass and force. In the English System, we use lbs. for both. In the Metric System, no one knows what a Newton is and probably have not heard the term before.

Edit: And, yet another layer of the jacked-up-ness is that "foot-pound" (work) is not the same as "pound-foot" (torque) in the English system. And, this is expressed backwards on most torque gauges and inconsistent from how the metric system expresses torque (force-distance).
I hereby request that Dan ban non-metric units for any and all technical discussions on ST.
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Re: legos, may explain low rpm vs high rpm in cyclist [Ai_1] [ In reply to ]
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Ai_1 wrote:
I hereby request that Dan ban non-metric units for any and all technical discussions on ST.
Haha... Forget world peace. If we could just all use the SI system, the world would be a better place. All my education was SI, while almost all my real-world application is Imperial. It seems far more probable that we could end war and hate before we eliminate the Imperial system of measure.
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Re: legos, may explain low rpm vs high rpm in cyclist [exxxviii] [ In reply to ]
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exxxviii wrote:
Ai_1 wrote:
I hereby request that Dan ban non-metric units for any and all technical discussions on ST.
Haha... Forget world peace. If we could just all use the SI system, the world would be a better place. All my education was SI, while almost all my real-world application is Imperial. It seems far more probable that we could end war and hate before we eliminate the Imperial system of measure.

To help, 746 watts = 1 horsepower. Yes, metric is better
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