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Re: Anyone with an FTP above 350w using short cranks? [RowToTri] [ In reply to ]
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RowToTri wrote:


What is "appropriate cadence"? Does it get higher as crank length gets shorter?

I also think that you need to include some metric for the appropriateness of the short crank to the fit of the rider. I would not be surprised if in the population of your riders, as FTP goes up, height goes up and therefore the usefulness of a short crank for fit goes down.


Agreed. I'm 6'3" and ftp near 350 and tried moving to shorter cranks and felt like I was throwing away the natural leverage my long legs provide. The wider the diameter, the less force you have to apply at any given moment, delaying fatigue. If the crank length better fits your natural stride length, then your effort is easier because it fits your body geometry. But if you try to cram in smaller rotations, then you have to generate more torque to get a rotation, which is throwing away the longer levers you are carrying on you already - Like running short steps with heavy shoes for no reason. If you are going to put weights on a flywheel, put them out at 175 cm instead of 160 cm to get more power out of the system more easily. But as pointed out, you first have to have enough breathing room (engine compartment, height) to let a 175 cm flywheel spin freely under the air intake (lungs) in the first place. By the time you get up to 6'3", your chest in aero is clearing that flywheel pretty good. A beer gut becomes a bigger problem than crank length.

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Last edited by: ZenTriBrett: Feb 26, 19 10:54
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Re: Anyone with an FTP above 350w using short cranks? [RowToTri] [ In reply to ]
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RowToTri wrote:
Are you the Jim Martin that did a study comparing power output of stiff cycling shoes and clipless pedals vs. running shoes on flat pedals?
At one point some years ago we were interested in bike shoes with only half the sole being stiff. Pearl Izumi made us a pair and we got some pilot data but we never did a full study.
Do you have a link to the study?
Cheers,
Jim
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Re: Anyone with an FTP above 350w using short cranks? [Hesiod] [ In reply to ]
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Hesiod wrote:
Ok. Those are big differences. But I think I’d be working really hard to get 170’s around to the power phase at 90rpms.

Is there a way of taking into account that we all mash through the power phase...even when we are trying to be smooth? I feel like I’m coming around quicker and easier on short cranks and getting to the mash with less work. Idk. I have no science to the madness...but I am conscious of applying power for a little spurt. I get a smooth rhythm. Short cranks feel like less work overall...

How does that fit with the numbers? Does not applying equal pressure change the overall efficiency?


I suspect you are right that you would have difficulty turning 170's at 90 rpm as most people naturally have lower rpm as crank length get's longer because I think most people apply close to the same force to the pedals when they change crank length - rpm adjusts to keep power the same. Sorta.

To do the analysis on "mashing" vs. perfect circular pedaling would take more time than I want to put into it - probably could do a simulation in engineering equation solver or something. It might change your metabolic efficiency (i don't know) but it will not change mechanical efficiency. Pedaling style can also affect how many muscles are used, at what % of their maximum force they are being used and therefore affect muscle fatigue while aerobic cost remains the same.

But even with mashing, the relative difference in pedal force will be the same.

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Last edited by: RowToTri: Feb 26, 19 10:47
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Re: Anyone with an FTP above 350w using short cranks? [Bio_McGeek] [ In reply to ]
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Bio_McGeek wrote:
RowToTri wrote:
Are you the Jim Martin that did a study comparing power output of stiff cycling shoes and clipless pedals vs. running shoes on flat pedals?

At one point some years ago we were interested in bike shoes with only half the sole being stiff. Pearl Izumi made us a pair and we got some pilot data but we never did a full study.
Do you have a link to the study?
Cheers,
Jim


No - Philip Majure (formerly of Pearl Izumi) was telling me about it though. I would love to see it. I'm working on a shoe/pedal system right now for an athlete to use in the mixed relay in the 2020 olympics and I would love to see that data....

Edit: though really what I'd like to see is if a running shoe midsole between the foot and a stiff pedal hurts power output. I found one study on that but it was at very low power levels.

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Last edited by: RowToTri: Feb 26, 19 10:52
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Re: Anyone with an FTP above 350w using short cranks? [Hesiod] [ In reply to ]
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Hesiod wrote:
My ftp has been consistently 340-360. Off season around 340. When training smart, 360. Crank-length is 145. Avg cadence when riding at ftp is around 83-85.

For reference, I’m 5’9” and 150lbs.

Damn you!

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Re: Anyone with an FTP above 350w using short cranks? [RowToTri] [ In reply to ]
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I had a foot injury and switched to running shoes on big flat pedals on my trainer rides for a year and power was exactly the same after just a couple of rides getting used to it. On top of that, there was a big benefit on longer rides, where not being locked in allowed me to adjust front/back on the pedals and saddle all I wanted to remain comfortable. It has a lot of endurance benefits for 112 miles and then running, which won't show in a study looking at just power at the pedal. My experience shows that people should try it if they feel the need. PM me and I can dig up the pedal details I used.
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Re: Anyone with an FTP above 350w using short cranks? [ZenTriBrett] [ In reply to ]
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Thanks! this will be for a very short (5km), very hard bike ride! And then a very fast 2km run after. There's no off the shelf pedal or shoe that meets the athlete's requirements, so we are working on a system to see if we can come up with something that works.

-------------
Ed O'Malley
www.VeloVetta.com
VeloVetta is developing AERO cycling shoes with CFD and wind tunnel testing.
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Re: Anyone with an FTP above 350w using short cranks? [Hesiod] [ In reply to ]
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First you say this:

I don’t think crank length matters as much as people whine on here. It’s mental.

And then you follow up with this:


I went shorter to ride more aero. Drop my front end, lift my back end. And open my hips. I feel comfortable in aero and my knees don’t smack my belly.

So which is it, mental, or all the physical things you listed?? (-;
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Re: Anyone with an FTP above 350w using short cranks? [TriByran] [ In reply to ]
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My threshold was about 375 when I rode 355watts for a hot 40k time trial on 155s. I had played with crank length for years. On my 785mm seat height on those 155s, I was equally happy on 160s, but did not feel correct after repeated trials on 150s. Getting down to 165 from 172.5 was a huge improvement. And 160mm was definitely better than 165mm.

My understanding of those particular crank lengths for myself came about from doing repeated (like everyday) threshold sessions on my fit bike and changing crank lengths OFTEN. The more you change them, the more tuned in you become to the effects. I knew if I was feeling fresh, the 160s would feel better, but if I was fatigued I liked the 155s better that day.

You can have too much knee flexion at the top of the stroke, so you shorten the crank. You can also have too little flexion, so you have made the crank too short. There is a range of crank lengths that the majority seem to fall into as a function of their seat height, but mitigating factors can indeed include FTP, with stronger riders tolerating longer cranks a bit better, while still generally trending to shorter than stock sizes.

I have not fit anyone who has chosen over 165mm in a long time. Including an 88cm seat height / 400 watt FTP pro on 165s, another 83cm seat height 360 watt FTP pro on 165s. You just gotta have a process that involves the rider, helps them find their positional limit, and zero in their awareness and your eyeballs on the specific areas and angles that are limiting further position improvements. Then maybe crank length helps solve some of those problems.

You have to be able to achieve and recognize when a rider is at basically the hip angle / thigh to torso / knee flexion limit of their existing crank. If you can't do that, there is probably no "a-ha!" moment for the rider when changing cranks.


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Re: Anyone with an FTP above 350w using short cranks? [monty] [ In reply to ]
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Do I contradict myself? Very well then. I contradict myself. I contain multitudes.

It’s mental refers to the idea that it is harder or easier. I take that as a perceived difference. However, physics apparently differs from my theory and indeed it does take more force to move a shorter lever. So I’m wrong.

As for the physical benefits. I also bet I’m not any more aero than I was with longer cranks. I suspect I would benefit from small and careful attention to aero details a great deal more than I do from playing around with crank lengths.
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Re: Anyone with an FTP above 350w using short cranks? [Hesiod] [ In reply to ]
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I also bet I’m not any more aero than I was with longer cranks.//

Well, what crank do you think is more aero all things being equal, the longer one or shorter one? And the things you do when you shorten cranks have a tendency to make one more aero, so there is that. You dont have to think about it, you just do it and there you have it, flatter back, perhaps better hole punched into the wind up front, and you can ride it longer, all aero benefits..


So I would take your bet...(-;
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Re: Anyone with an FTP above 350w using short cranks? [FindinFreestyle] [ In reply to ]
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I like 165 personally.
I found 155 just a little too short for my gargantuan legs (37 inches) I found they just felt too punchy, I used them for a year, including an Ironman with a top 10 bike split. But I could never make them work for harder sustained efforts around FTP
I’d like to trial 160 at some point
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Re: Anyone with an FTP above 350w using short cranks? [RowToTri] [ In reply to ]
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Small world! I'd still like to do something with it. Need to find an undergraduate who's keen on cycling.
Would like to get a size run of some brand of shoe, Chucks maybe. Figure out a way mount cleats on em and them compare with standard stiff cycling shoes. I wouldn't expect to see any difference in max sprinting power.

RowToTri wrote:
Bio_McGeek wrote:
RowToTri wrote:
Are you the Jim Martin that did a study comparing power output of stiff cycling shoes and clipless pedals vs. running shoes on flat pedals?

At one point some years ago we were interested in bike shoes with only half the sole being stiff. Pearl Izumi made us a pair and we got some pilot data but we never did a full study.
Do you have a link to the study?
Cheers,
Jim


No - Philip Majure (formerly of Pearl Izumi) was telling me about it though. I would love to see it. I'm working on a shoe/pedal system right now for an athlete to use in the mixed relay in the 2020 olympics and I would love to see that data....

Edit: though really what I'd like to see is if a running shoe midsole between the foot and a stiff pedal hurts power output. I found one study on that but it was at very low power levels.
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Re: Anyone with an FTP above 350w using short cranks? [TriByran] [ In reply to ]
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TriByran wrote:
Just a question as per title.

I'm determining short as 160mm or less.

Currently doing some testing with a range of athletes including a few pro cyclists and we are finding an interesting relationship between power output in AERO position and minimal acceptable crank length.

Please note this is in AERO position and is OUTSIDE.
Therefore has no relationship with the studies on crank length done sat up on an erg.


Without quantifying the weight of the person you are not going to gain much unless that is really part of your study that absolute watts matter. Fwiw, I have had an ftp of 5.14 w/kg at least during my peak, right at your 350 target at 68kg. I ran cranks as low as 115mm. 115 was a challenge for different reasons but there was no discernible drop off in power. I didn't like them for climbing however. Didn't spend much time on 115s but 145 were much more doable. I am a huge fan of short cranks for everything, road, tri, MTB.


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Re: Anyone with an FTP above 350w using short cranks? [Thomas Gerlach] [ In reply to ]
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Thanks Thomas, what’s your leg length?
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Re: Anyone with an FTP above 350w using short cranks? [RowToTri] [ In reply to ]
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RowToTri wrote:
Thanks! this will be for a very short (5km), very hard bike ride! And then a very fast 2km run after. There's no off the shelf pedal or shoe that meets the athlete's requirements, so we are working on a system to see if we can come up with something that works.


I found what worked great was lightweight but really large and super flat downhill mountain bike pedals like these. And then trail running shoes for the stiffer soles. You get all the stiffness of being locked in with bike shoes, but the freedom to move around all you want. It's amazing.

I did it to help get over plantar fasciitis and it worked great. I was able to keep riding and racing and move my foot around as needed to relieve pain as it developed. I won a local 100 mile gran fondo on flat pedals and running shoes, same power as the year before, no problems. It was funny getting off the bike and walking around to get beer like a normal person, no clack-clack like the "real" cyclists. ;)

I'm back on clipless now, but for no reason in particular.
Last edited by: ZenTriBrett: Feb 26, 19 13:30
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Re: Anyone with an FTP above 350w using short cranks? [TriByran] [ In reply to ]
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TriByran wrote:
Thanks Thomas, what’s your leg length?

I was 5 feet 8.75 with an inseam of 33.63. But I somehow "grew" in the last 18 months and I am closer to 5 10, haven't measured my inseam to see if it changed at all. I never did any aero testing, mainly because it was a PITA. I did the adjustable cranks via PowerCranks that allowed me to play around with it. I did slap aerobars on the commuter bike for a short while. I really like the 160-165mm range.


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Re: Anyone with an FTP above 350w using short cranks? [Thomas Gerlach] [ In reply to ]
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Thomas Gerlach wrote:
TriByran wrote:
Thanks Thomas, what’s your leg length?


I was 5 feet 8.75 with an inseam of 33.63.


Lol...you couldn't just round that to 9, and 34 (or 33.5)?

I have nothing else to add.
Last edited by: Tom_hampton: Feb 26, 19 13:45
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Re: Anyone with an FTP above 350w using short cranks? [domingjm] [ In reply to ]
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Ha! Thanks...I guess. ᕦ(ò_óˇ)ᕤ
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