Typical stiffness discrepancy between crank arms.
11-01-19, 10:19 AM
#26
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11-01-19, 11:15 AM
#27
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A Formula 1 car avoids this design flaw, I suggest you upgrade!
To the OP... Yes, as an engineer, I am sure that I could calculate slightly more flex on the left side crank arm due to having to transmit torque through the crank axle to the drive side. However, that difference in flex is going to be minuscule, something best measured with tools a machinist would use. If you are riding in regular street shoes, I would expect the flex in the sole of your shoe to be larger than in the crank. I would agree with those above that this is a setup or bike fit issue. Our bodies are often fairly asymmetrical whether it is noticed or not.
To the OP... Yes, as an engineer, I am sure that I could calculate slightly more flex on the left side crank arm due to having to transmit torque through the crank axle to the drive side. However, that difference in flex is going to be minuscule, something best measured with tools a machinist would use. If you are riding in regular street shoes, I would expect the flex in the sole of your shoe to be larger than in the crank. I would agree with those above that this is a setup or bike fit issue. Our bodies are often fairly asymmetrical whether it is noticed or not.
I thought about this and realized there's all sorts of reasons we don't use our legs symmetrically on long rides that have nothing to do with routine pedalling motion. For example, I just noticed that I always go through the same routine when I start up when the light turns green--my right foot starts on the ground, and my left foot is on the pedal at the highest position. I do two little pushes with my right foot then put it on the pedal while my left foot exerts a big push down on the pedal, then I start spinning to accelerate. No question in my mind that my left leg puts out just a little bit more torque at every stop than the right one. On a very long ride, I might repeat that sequence several dozen times. I haven't noticed any difference in fatigue between the two legs, but it makes me think there are lots of actions we take without thinking that might favor one leg systematically over another.
11-01-19, 11:26 AM
#28
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About a year ago first time putting any weight on my leg:
Anyhow, most people are not that extreme obviously. Just keep riding is usually all that needs to be done.
But yes, in some cases you adapt the bike. See adaptive cycling forum here.
But in atrophy cases like mine, pros help. I miss my physical therapist honestly. I had to mindfully make sure that I wasn't cheating with my right leg.
Many crank power meters assume rider symmetry. We aren't. But you don't need a power meter.
The easiest real world way to find out is to ride on a quiet bike path or quiet road. Slight uphill useful, and nobbies help but road tires work too.
WAAAaaahWAAAaaahWAAAaaahWAAAaaah. (Symmetric power application.)
WAAAaaahWAAAaaahWAAAaaahWAAAaaah. (Asymmetric power application.)
WAAAaaahwaaaaaahWAAAaaahwaaaaaah. (Physical therapy to work that left leg.)
WAAAaaaaaaaaaaaahWAAAaaaaaaaaaaaah. (Single-leg training.)
And of course:
WAAAWAAAWAAAWAAAWAAAWAAAWAAAWAAA. (Spin class.)
BOOMBOOMBOOMBOOMBOOMBOOMBOOMBOOM. (Spin class bass line.)
KEEP IT QUICK COME ON. STARTING TO BURN A LITTLE? (Spin class instructor.)
Finally, some asymmetry is perfectly normal. Effects runners too. Before you think symmetric is obvioulsy better, Usain Bolt has an asymmetric stride.
-mr. bill
Anyhow, most people are not that extreme obviously. Just keep riding is usually all that needs to be done.
But yes, in some cases you adapt the bike. See adaptive cycling forum here.
But in atrophy cases like mine, pros help. I miss my physical therapist honestly. I had to mindfully make sure that I wasn't cheating with my right leg.
Many crank power meters assume rider symmetry. We aren't. But you don't need a power meter.
The easiest real world way to find out is to ride on a quiet bike path or quiet road. Slight uphill useful, and nobbies help but road tires work too.
WAAAaaahWAAAaaahWAAAaaahWAAAaaah. (Symmetric power application.)
WAAAaaahWAAAaaahWAAAaaahWAAAaaah. (Asymmetric power application.)
WAAAaaahwaaaaaahWAAAaaahwaaaaaah. (Physical therapy to work that left leg.)
WAAAaaaaaaaaaaaahWAAAaaaaaaaaaaaah. (Single-leg training.)
And of course:
WAAAWAAAWAAAWAAAWAAAWAAAWAAAWAAA. (Spin class.)
BOOMBOOMBOOMBOOMBOOMBOOMBOOMBOOM. (Spin class bass line.)
KEEP IT QUICK COME ON. STARTING TO BURN A LITTLE? (Spin class instructor.)
Finally, some asymmetry is perfectly normal. Effects runners too. Before you think symmetric is obvioulsy better, Usain Bolt has an asymmetric stride.
-mr. bill
Just for fun, I will occasionally make my hand positions asymmetric by putting one on the hood and one on the drop then standing on the pedals. I can accelerate like crazy doing that because the rocking of the bike gives a little leverage boost. Probably do more of it if it wasn't quite so stupid-looking.
11-01-19, 11:38 AM
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I would have said the same thing my first 60 years. Went to a PT for an unrelated issue. She had me walk away from her the length of the room and back and immediately told my right leg was shorter than the left. Sent my home with 1/2" lifts for all my right shoes. I modified (with her approval - she is an excellent and very strong rider) all my right cycling shoes with a 1/4" plate over the cleats. Life changing. Ride changing.
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11-01-19, 01:00 PM
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11-01-19, 01:17 PM
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11-01-19, 01:46 PM
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Wrong kind of bar to be really distracting. Pie charts make me hungry.
11-01-19, 01:52 PM
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Might have been helpful if they actually labelled the units on the Y axis. As it is, I can't figure out if this is supposed to mean that higher values equal more flex per weight or more weight per flex.
Wrong kind of bar to be really distracting. Pie charts make me hungry.
Wrong kind of bar to be really distracting. Pie charts make me hungry.
In all seriousness, I think the chart is supposed to be the stiffness to weight ratio (where a higher figure would be desirable), and it was just done by an idiot. Bugs me when people don't know how to use < or > either.
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11-01-19, 03:18 PM
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11-01-19, 05:04 PM
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I don't know what caused your sore leg, but it sure as hell wasn't the crankset.
11-01-19, 06:08 PM
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One thing can happen: Something else in your life might be asymmetrical, ranging from driving a car to how you sit at a computer. Then the strenuous exercise exacerbates the imbalance and you get pain on one side. I find that whenever I get a "crick" or pain from riding, it's always on one side, but the side is unpredictable. The exception is neck pain related to years of computer use.
11-02-19, 01:54 AM
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So unless op returns, this thread is officially absurd. I think we've narrowed the cause down to everything in the world that isn't the crank arms.
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11-02-19, 04:17 AM
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I totally agree with this.
But just to be sure, look at the center of the flexier arm, and make sure there is a large-headed bolt inside the hole in the center. Give the bolt a wiggle and see if it seems tight. If so, good. If not, it needs to be tightened. If you've never done this take it to a bike shop and ask them to torque it correctly.
Also check the bolts that hold the rings onto the spider. There needs to be five for the middle ring and five in the inner ring, and they all need to be tight. Ask a shop to tighten them correctly, if there is any question.
They SHOULD not loosen, but it can happen if they have not been disturbed since leaving the factory.
On the muscular front, take some more frequent rides of 20 miles or so, then go back to your 53 mile route. The multiple shorter rides should be toning up your legs.
But just to be sure, look at the center of the flexier arm, and make sure there is a large-headed bolt inside the hole in the center. Give the bolt a wiggle and see if it seems tight. If so, good. If not, it needs to be tightened. If you've never done this take it to a bike shop and ask them to torque it correctly.
Also check the bolts that hold the rings onto the spider. There needs to be five for the middle ring and five in the inner ring, and they all need to be tight. Ask a shop to tighten them correctly, if there is any question.
They SHOULD not loosen, but it can happen if they have not been disturbed since leaving the factory.
On the muscular front, take some more frequent rides of 20 miles or so, then go back to your 53 mile route. The multiple shorter rides should be toning up your legs.
11-02-19, 06:58 PM
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the left will always be a problem, because the right does all the work.
