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Old 03-09-09, 12:40 PM   #1
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Crank Torque question

I've been noticing looking at my data for a while that my max torque is almost always 1800 lb-in +/- 10, pretty much regardless of the ride type or general effort levels. I'm wondering if this is some kind of physiological limit of mine or if it is just an artifact of the way the power meter works. I don't think they are just random spikes as they occur on the leading edge of any large power increase, such as starting from a stop at a light, especially if I am trackstanding, or the start of a power climb or sprint. Is this basically my "jump"?
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Old 03-09-09, 01:06 PM   #2
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How much do you weigh? How long are your crankarms?
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Old 03-09-09, 01:11 PM   #3
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~64kg, 172.5mm
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Old 03-09-09, 01:12 PM   #4
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Most of all I find the consistency surprising.
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Old 03-09-09, 02:11 PM   #5
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I never paid attention to the torque numbers before, but when I checked just now, my numbers are not nearly that consistent, even for similar types of rides and workouts. The peaks seem to range between 900 and 1400, with many around 1200.
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Old 03-09-09, 02:28 PM   #6
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Well, the torque generated at a 90* angle by applying all of your body weight to a 17.25cm lever arm is 108.265416 newton-meters, which is 958.229 672 44 pound inch.

That's 1/2 of the "consistent" torque you're seeing, I'm sure there's some relationship there.
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Old 03-09-09, 02:36 PM   #7
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The other thing I realized at lunch was that the data file from the Garmin doesn't actually store torque so WKO must be back-calculating it out of power and cadence... but the power meter is actually transmitting torque and cadence and the Garmin is just multiplying them and storing the result, so it should be ok.
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Old 03-09-09, 03:13 PM   #8
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Your max torque is limited by leg strength. And it'll probably always occur when starting from a stop in a large gear. Basically, you are applying, say, 400-500W at essentially zero speed, which will give you maximum torque.

To put it in perspecive, a full-on, 1300W sprint at 120rpm cadence will give you about 900in-lbf of torque (just math: power divided by cadence with appropriate units = torque). A standing start at 400W and 20rpm cadence will give you about 1700in-lbf of torque, which is something like the max you are seeing.

So, the max torque number you are seeing is probably just you starting up from stop signs and such, which won't change regardless of ride intensity.
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Old 03-09-09, 03:18 PM   #9
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^^^ That's sort of what I was figuring. Was curious if that is an indication of a "limiter" that can be improved with leg strength workouts to give me better max power, or if it is only weight dependent and pretty much meaningless. E.g. if I could put out more max torque, would that give me a better jump?
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Old 03-09-09, 03:30 PM   #10
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Quote:
Originally Posted by umd View Post
^^^ That's sort of what I was figuring. Was curious if that is an indication of a "limiter" that can be improved with leg strength workouts to give me better max power, or if it is only weight dependent and pretty much meaningless. E.g. if I could put out more max torque, would that give me a better jump?
Definitely. More torque means better acceleration, end of story. When you start from a standing start, you are doing more than just standing on the pedals. You are bracing yourself against the handlebars and your leg strength contributes a lot to the torque.

My calc above and bdchung's calc with body weight would indicate that about half of your standing start torque is due to leg strength.
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Old 03-09-09, 03:35 PM   #11
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Also keep in mind that, unless you are specializing in the kilo on the track, absolute leg strength doesn't do anything to help a jump unless you can apply that strength at speed. If you don't have those fast twitch muscle fibers, no amount of strength training will morph you into a sprinter.
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