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  #1381  
Old 05-04-12, 05:30
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Martin318is Martin318is is offline
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I stand corrected...

Does this also apply to the Serrota Biometric Fit jig?
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  #1382  
Old 05-04-12, 05:38
FrankDay FrankDay is offline
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Originally Posted by Martin318is View Post
I stand corrected...

Does this also apply to the Serrota Biometric Fit jig?
I am not familiar with that device but my guess is "yes" because I am only familiar with a couple of devices that actually measure right and left pedal dynamics separately. They tend to be either only available in universities or on very expensive ($25-50k) machines. If the Garmin Vector ever becomes available hopefully that will change.

Edit: Garmin Vector isn't the only hope here. I am also aware of two other products in development that will do this, one in Europe and one in Australia. I think each of these will have the PM's in the crank arm. At least one is looking to see if the device can be incorporated into the PowerCranks.
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Last edited by FrankDay; 05-04-12 at 05:50.
  #1383  
Old 05-04-12, 15:16
sciguy sciguy is offline
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Originally Posted by FrankDay View Post
Courtney Ogden raced on PC's at Ironman Canada a few years ago and had the fastest bike split of the day. Drew Peterson did the Everest Challenge on 110 mm PC's last year and finished in the top 10 overall.

If a cyclist is not adequately trained on the PC's they will slow you down. If the cyclist is adequately trained on them, they will not.
Would that be Courtney Ogden who has seemed to be suffering from a series of knee injuries for the past several years? Several of us are wondering if his injuries might relate to the use either PowerCranks, shorter cranks or both.

YMMV,

Hugh
  #1384  
Old 05-04-12, 15:45
acoggan acoggan is offline
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Originally Posted by FrankDay View Post
Prove that statement when one is considering what happens in the aero/TT position. While Martin's study did show a small variation over a large range one can assume his subjects were mostly upright (he did not specify), since he was measuring maximum power. If one were to repeat that study with cyclists in the TT position my guess is the results would be skewed even shorter and with larger variation. And, if one were to repeat that study looking at sustainable power in the aero position vs crank length I would expect the results to be skewed even shorter. Unless you can prove your above contention with real studies I would suggest that you are extrapolating from upright position data what you expect and simply blowing a lot of hot air our way through your computer keyboard. I mean, you do sayWhy on earth wouldn't you think that wouldn't have an effect on the amount of power they might be able to generate? And, if it did, why wouldn't it be a "panacea", at least for them?
1. The subjects in Jim's studies were all experienced cyclists, who were free to adopt whatever thigh-torso angle they felt allowed them to generate maximal power for a very short duration while seated (naturally, I had my hands in the drops). I would therefore argue that it is quite likely they did so, i.e., "body wisdom" is a powerful influence...this is, after all, why you see pursuiters invariably creeping onto the nose of their saddle late in race, or (more relevantly) why steep-seattube-angled TT/tri bikes were invented in the first place. Thus, while it is possible that cranks even shorter than 145 mm might (or might not) be better when a rider is forced to assume an overly-acute thigh-torso angle, that is really putting the cart before the horse...the goal is to maximize power:CdA, not just minimize CdA, so you never want to adopt a position that compromises your power *unless* you know that the improvement in CdA is worth it.

2. In keeping with the above, I have measured my both my CdA and my sustainable power in a wide range of aero of positions while using a wide range of crank lengths. What I have found is that if I go too low, my power drops more than my CdA, and shortening the cranks by up to 22 mm doesn't help.

3. Panacea (n): a. A remedy for all diseases and ills; cure-all. b. An answer or solution for all problems or difficulties.
  #1385  
Old 05-04-12, 15:49
acoggan acoggan is offline
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Originally Posted by FrankDay View Post
Then, would you agree, that pedaling technique is not "natural"? That what we do in pedaling a bicycle depends mostly on how we were taught when learning and not what God has predetermined, through evolution, is best for us?
On the contrary: pedaling is an extremely "natural" motion, in that 1) we activate the same muscles in essentially the same sequence as when walking or running, and 2) even pedaling backwards has very little effect on this pattern. IOW, we pedal using essentially the same evolutionarily-designed motor program as we use during upright bipedal locomotion, with very little learning either necessary or beneficial.
  #1386  
Old 05-04-12, 15:50
acoggan acoggan is offline
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Originally Posted by coapman View Post
Expanding on above statement. Martin's research results are based on natural pedaling techniques where max torque is applied with a vertical downward force between 2 -4 o'c and where only the lower body is used. With this technique changes in cadence are easier to make in keeping with the change in crank length. But if you are using a technique which can almost double the cumulative torque from each pedal stroke by starting max torque around 11 o'c, where forward and downward pedal forces are used, which uses both the upper and lower body in generating the crank torque and which works best using the higher gears, I don't believe you would get the same 'change of crank length' results.
Back to your same ol' schtick, I see. Thank goodness...I'd start to worry that the world was coming to an end if you or Frank ever deviated from your "performance art".
  #1387  
Old 05-04-12, 15:57
acoggan acoggan is offline
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Originally Posted by TarmacExpert View Post
IMO Frank has a fair point, here, in that the results of Martin's study may well have been different with riders in the TT position.
Not for me (or, apparently, Chris Boardman).

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Originally Posted by TarmacExpert View Post
It depends what exactly you mean by large, of course, but I'm surprised you haven't thought it worthwhile to field test longer cranks. 190mm instead of 170mm would get your knee 4cm higher relative to your hip at the top of the pedal stroke (assuming you move both saddle and pads down 2cm), so if there were no adverse impact on power production, this might be expected to give a small but perhaps worthwhile aero gain.
At the risk of giving away too much information: Your feet and lower legs are a far greater source of aerodynamic drag than your thighs, which are 1) far closer to horizontal, at least at the top of the pedal stroke, and 2) drafting, to at least some degree, behind your arms. Longer cranks therefore don't provide a significant aero advantage, but do move you that much closer to the "tipping point" with respect to the minimal acceptable thigh-torso angle (which for me is at the point that my thighs almost contact my lower ribs...not because of any interference effect or restriction of breathing, that's just a consistent reference point).
  #1388  
Old 05-04-12, 15:59
acoggan acoggan is offline
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Originally Posted by FrankDay View Post
As long as the people are adequately trained on their PC's and as long as the fit is good on the PC's I think you will find no difference
What happened to the 40% improvement?
  #1389  
Old 05-04-12, 19:36
sciguy sciguy is offline
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Originally Posted by FrankDay View Post
It is just reports like this that have helped me to conclude that PowerCranks are an excellent bike fitting tool because it is not possible to know on regular cranks if one is losing much power or not. And, it is reports such as this (and my own experience) that got me to thinking about going to shorter cranks.
It's posts like this one that brings to mind the old expression "cures what ails you" often associated with snake oil salesmen........oooops

Hugh
  #1390  
Old 05-05-12, 18:29
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Originally Posted by Martin318is View Post
Personally, I'd go a step further and go to an experienced bike fitter and have them do an assessment and any adjustments for you. Unless you are trying something dramatic, you should be able to make most of the changes on the one day - if done correctly. Changing Q Factor is theoretically a minor change but it depends what your starting point is. In my own case, my position had seemed fine but on inspection I was already irritating the ITB. Any movement of my feet closer together would have made this worse.
So I ran a little experiment. Keep in mind my baseline was a position that an experienced fitter helped me with.

I moved the cleats so my feet came inwards about 3-4 mm each. After a slight tweak to saddle height and a very slight tweak to saddle fore-aft, the position is comfortable and I have ridden and raced with it for 5 days now. The power is the same (using a power meter on the indoor trainer), although the feel is better, possibly because my feet are now more 'over' the pedals.

Obviously, I am not testing in a wind tunnel, so take this with a grain of salt - the position seems to be faster. Looking at average power for segments of road has yielded faster speeds, given highly similar conditions (in terms of wind, temp, time of day).

Felt great in the race too.

Just thought I'd share the experiment results
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