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I have an older stationary bike with a weighted wheel and I'm trying to calibrate distances based on pedal rotations when operating it. Is there a 'standard' number of full pedal rotations per unit kilometer?

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  • Don't forget many stationary bikes have a range of "gears" anyway, or at least that's how the resistance control is presented
    – Chris H
    Commented Feb 7, 2022 at 11:19
  • As a rough average, 80 rpm cadence and 20 km/h speed gives 240 pedal rotations per kilometer.
    – jpa
    Commented Feb 7, 2022 at 17:58
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    If the bike is stationary, wouldn't it be infinity rotations per kilometer? ;)
    – Reid
    Commented Feb 7, 2022 at 22:58
  • One rotation of regular 700c wheel is about 2.2m, gear ratio for regular ride is somewhere between 2 and 3 which give 150-230 rotations per km (very close to @jpa estimate of 240 - for higher cadence you likely use lower ratios) Commented Feb 8, 2022 at 2:30
  • @Somekindarazzmatazz Could you re-phrase that? What could the bike having a weighted wheel change? How could a 'standard' number of pedal rotations per unit kilometer be useful, without specifying the gear ratios? Commented Feb 8, 2022 at 21:44

5 Answers 5

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I doubt so, every stationary bike manufacturer can make it differently. But it would not make that much sense for comparison anyway. Every kilometer takes a different effort based on the slope, aerodynamic resistance, rolling resistance (outdoors), or resistance settings (indoor). A modern trainer will give you a very accurate number for the distance, but a number that is almost meaningless. The power that you have to produce is what matters.

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No. The main problem is the "resistance" setting which could range from zero/none right up to high/hard, (or Bart Simpson riding at night with a bottle dynamo on)

I presume you're looking for some way to equate stationary bike rides with real outdoor riding. So instead - focus on consistency.

Idea: Ride a conventional bike at a fair intensity/effort for 10 minutes, and check your heart rate. Then ride your stationary bike for 10 minutes at the same intensity and check your heart rate. If the HR of the stationary ride is significantly lower/higher then adjust the resistance. Rest for 10~30 minutes and try again. If you're within 10 BPM you're close enough.

Now its dialled-in, you can try for the same effort for as long as you choose. Or if the stationary bike has a display, try for as many kilometres in 10 minutes as possible, and log that number as your result.

  • 10 km/h = 1.6 km or ~1 mile in 10 minutes
  • 30 km/h = 5 km in 10 minutes

Logging your output shows improvements over time, and that's what you really want to see for comparison purposes.

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    Bart Simpson dynamo reference: youtu.be/i7kgzgcqe5s Commented Feb 7, 2022 at 19:06
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    @WaterMolecule thank you - German Bart sounds... unexpectedly different. (assumed because it was youtube.de)
    – Criggie
    Commented Feb 8, 2022 at 9:08
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    @Criggie That isn't german. Dunno which language (sounds a bit like a roman language), but Bart definitely does not speak german in the video linked by WaterMolecule. (You may want to try and find Marge in german... now that's a difference to english.)
    – orithena
    Commented Feb 9, 2022 at 13:31
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What matters is your power output.

On a real bike speed by itself is relatively meaningless. You can do a slow 15km/h but still be outputting 200W because there is a headwind or because it’s a 7% grade. You can do 30km/h on flat terrain but only need 140W because you are riding a high-end aerodynamic road bike.

Of course on a stationary bike one could convert power to some virtual “speed”. There are some calculators on the internet which can estimate speed based on power, weight, bicycle type, grade and so on. For example this one: http://www.kreuzotter.de/english/espeed.htm

If you can find a way to measure (or at least estimate) power output on your stationary bike you could do these kinds of conversions if you feel like it. Maybe you can install bicycle pedals with a built-in power meter (e.g. Favero Assioma Duo pedals).

Edit: An important question is also: What’s the benefit of knowing your power output? I think the main point is that it can help with training because it allows you to pace yourself. For example to ride intervals at a constant 300W for 5 minutes or long endurance rides at 160W for 4 hours. But in the end the power value itself doesn’t have any deeper meaning. If you know that you can (barely) sustain resistance level 5 at 90rpm for 5 minutes on your stationary trainer or ride 4 hours at resistance level 3 that’s just as valuable.

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  • Pedal based PM is a good idea, but might be a little more tricky than it sounds - think they typically need to know the crank length?
    – Andy P
    Commented Feb 7, 2022 at 15:57
  • @AndyP: Yes, for pedal based power meters you have to configure crank length. I think most are set to 172.5mm per default.
    – Michael
    Commented Feb 7, 2022 at 16:35
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When you say "older stationary bike" the ones with a fixed gear on something that looks like a roughly 20 inch wheel that uses brake pads for resistance come to mind.

Like this one
enter image description here

The pictured type comes with a speedometer with integrated odometer.
enter image description here

There is no "standard". Different makers used different sized wheels and different gearing combinations over time.

You can calculate the number you are looking for.

First, calculate the circumference of the wheel
Second, count how many times the wheel rotates per pedal rotation
Third, multiply the wheel rotations by the circumference to get distance traveled in one pedal rotation
Lastly divide one kilometer by the distance traveled in one pedal rotation to know how many full pedal rotations per kilometer

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    That will tell you the total distance moved by the wheel, but there's not reason for it to be anything like the distance you'd do on a real outdoor bike for the same effort and duration. The effort outdoors goes mostly into pushing against air resistance, rolling resistance and hills, none of which apply indoors.
    – bdsl
    Commented Feb 7, 2022 at 21:45
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    @bdsl The question was about distance moved by the wheel so the answer addressed the question. Stationary bikes attempt to mimic road conditions using some type of resistance - adjustable brakes, magnetic resistance etc. It's never the same as the road and to some extent it does not matter. The goal is to get some exercise and a stationary bike set up correctly and ridden regularly can do that.
    – David D
    Commented Feb 8, 2022 at 13:15
  • Yes stationary bikes attempt to mimic road conditions, but I don't think they make any attempt to make the effort to move the wheel a certain distance comparable to the effort to move the same distance on a road. There's no reason to do that since normally the wheel distance on a stationary bike isn't observed.
    – bdsl
    Commented Feb 8, 2022 at 13:23
  • @bdsl I must be misunderstanding your point. No one asked any questions or made any claims about stationary bikes comparing to riding a real bike. The wheel distance is one on a stationary bike is observed on many models of stationary bike. I have added a picture to my answer showing the odometer on that model.
    – David D
    Commented Feb 8, 2022 at 15:24
  • THIS is the answer to the question asked. The other answer do a great job of pointing out why the question may have been the wrong one, but this actually answers it.
    – FreeMan
    Commented Feb 8, 2022 at 17:22
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After some consultation, we have agreed that the number of pedal revolutions per kilometer on a stationary bicycle is typically either zero or infinite, depending on the bike.

No middle ground on this one.

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    Zero or infinite is not helpful. Buy an inexpensive odometer, measure the circumference of the wheel, mount the gizmo, affix the measure magnet or whatever, tell the device "my wheel is 31.5 inches in diameter" or whatever, turn it on, pedal. Watch the numbers go up. Surely that is better than "zero or infinite"... Even a GPS, on the same route outside, is just an estimate, given the error rates. Did I ride 32.3, or 32.5, or 32.7 today? Meh, I did 32 miles.
    – railsdog
    Commented Feb 8, 2022 at 2:28
  • @railsdog that's a good suggestion, if the bike has none of that already. Go for X km regardless of how long it takes, or aim for a steady pace of Y km/h for the exercise's set duration. Consistency is the goal, or comparable numbers between days, and not comparing with any other bike.
    – Criggie
    Commented Feb 8, 2022 at 9:10

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