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power balance variation - road bike to tri bike
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Hi all
an interesting thing i've noticed is that while my power balance (as measured by garmin vectors) is pretty much 50/50% on my road bike, on the tri bike its often as much as 45/55%, as well as being a touch lower in total.
i'm not overly bothered whether i'm balanced or not, i just find it interesting that the balance differs between the different positions and would be interested in any theories as to why this might be and anything it might mean physiologically, bike fit or otherwise. i guess the hope being that i might be able to get the left leg power up to match that of the right since it can do it on the roadie.
the other piece of information the vectors give which could be related is that while my right side is pretty centred over the pedal, i typically have a left "platform center offset" of +10 or more (to the outside) on both bikes.
i did note today that my left leg felt like it was going knee out occasionally once i got tired, though i think the balance was pretty consistent even before then

anyone got any thoughts?
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Re: power balance variation - road bike to tri bike [pk1] [ In reply to ]
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With regard to the left/right balance, the first thing I'd check is saddle height to make sure your saddle isn't too high.

In my last bike fit, the fitter noted (with a laser line placed vertically on each leg) that my right knee would move about one kneecap width side to side throughout the pedal stroke. We switched orthotics (in my case to one of the specialized orthotics) and tweaked saddle height and now both knees track perfectly straight throughout the pedal stroke.

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Re: power balance variation - road bike to tri bike [pk1] [ In reply to ]
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As above poster said, check saddle height etc.

Are you using the same shoes? Cleat adjustment or a loose cleat can have a noticeable effect. Sole use of power balance for me was identifying a loose cleat.
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Re: power balance variation - road bike to tri bike [pk1] [ In reply to ]
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pk1 wrote:
Hi all
an interesting thing i've noticed is that while my power balance (as measured by garmin vectors) is pretty much 50/50% on my road bike, on the tri bike its often as much as 45/55%, as well as being a touch lower in total.
i'm not overly bothered whether i'm balanced or not, i just find it interesting that the balance differs between the different positions and would be interested in any theories as to why this might be and anything it might mean physiologically, bike fit or otherwise. i guess the hope being that i might be able to get the left leg power up to match that of the right since it can do it on the roadie.
the other piece of information the vectors give which could be related is that while my right side is pretty centred over the pedal, i typically have a left "platform center offset" of +10 or more (to the outside) on both bikes.
i did note today that my left leg felt like it was going knee out occasionally once i got tired, though i think the balance was pretty consistent even before then

anyone got any thoughts?

2 different position two different outcomes. This might be related to your flexibility, your hamstring tension, lower back issues, seat pressure points change and it could be pinching your nerve and affecting performance. Using shims to bring that +10 to something closer to ) could even it out but not necessarily, but it is good place to start, working on flexibility would be beneficial as well. Find somebody that specializes in physiological fit...
Shims can be cut out from 1mm thick old credit card and you can experiment with it yourself, Certain shoes with high arch will do the trick without the shims.

Eg. Bont shoes on my feet will have +10 offset and Bontrager will have 0, Bongrager are specifically supporting high arch. Everyone feet are different, but it is easy to sort this out if you talk to the good fitter.
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Re: power balance variation - road bike to tri bike [sebo2000] [ In reply to ]
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thanks for the input guys, a few things to look at. i'm struggling to find a good fitter in my area so trying to work a few things out on my own for the moment
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Re: power balance variation - road bike to tri bike [pk1] [ In reply to ]
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you've got a clear cut example of why single sided power measuring devices are not good.

power balance varies inter ride, intra ride, on different bikes, on different days, etc. really not much you can/should do about it.
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Re: power balance variation - road bike to tri bike [pk1] [ In reply to ]
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Definitely get with a bike fitter. Your bike position and/or your bike configuration could be a factor in the power imbalance. I saw something similar and wrote a blog post about my experience with dual sided power.

http://www.triplethreattough.com/blog/power-balance-and-shorter-cranks/



Tommy Johnson
Triple Threat Tough
USA Triathlon Coach
Tri Shop
Retul fitter / FIST fitter
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Re: power balance variation - road bike to tri bike [pk1] [ In reply to ]
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So, this is out there, but it is worth a look... Are the crank arms on your tri bike the same length? Someone here posted that they accidentally discovered they had different length crank arms. You never know until you look...
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Re: power balance variation - road bike to tri bike [exxxviii] [ In reply to ]
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exxxviii wrote:
So, this is out there, but it is worth a look... Are the crank arms on your tri bike the same length? Someone here posted that they accidentally discovered they had different length crank arms. You never know until you look...

pretty sure, but i will double check!
worth noting that they are 170mm vs 172.5 on the roadie
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