Ankling & Foot position as affected by Boom, Crank and Chainstay length
- Thread starter RojoRacing
- Start date
imvho the boom looks to be too far out, at the point on the chainset between where the hour hand is 2-4 o'clock your toes are more forward than your heel, I'd expect this to be the opposite way around with your heel being more forward than your toes, I believe the term is ''ankling''.
This is the way I pedal that I perfected on the wattbike but can still apply to riding a recumbent, and that is you'd kick forward or up through the dead spot in the case of riding a bent to the point where the hour hand would be on a clock if it was 10.30, and from here it is a straight forward leg press keeping the ankle and lower leg loose and wanting to drive the leg forward heel first. Doing the same with opposite leg brings the trailing leg back through the recovery phase and so it goes on.
Having said all this, you look in pain just clipping in, don't risk it. <neutral face smiley>
ratz
Wielder of the Rubber Mallet
Ok this could get complicated, you have been warned, there be angles a foot
Jason ankling is pretty solid and close to textbook to my eye, this was a topic I've been studying because of the way Larry and Eric Winn pedal compare to the way I do, trying to figure out why we do it differently and why I can't match what they are doing positionally; and lastly whether it mattered. I believe I have it figured out but had not had time to post about it.
According to current best practices that I have read about at, In the two non power phases of the stroke you heel should be a 20 degree up from being perpendicular to your body's vertical line. During the power stroke that should reduce to the range of 0 to -10 degrees How far towards -10 you get depends on your knees, leg length, and the strength of your calves. Good so far and matches @leetaylor55 assertion; standard text book and what one would expect on a Wattbike.
Drawing #1 is the Stand DF diagram for proper ankling, (borrowed from bicycling.com)
Drawing #2, below, is this same idea rotate 90 degrees if the athlete where laying on his back, but maintaining the same pedaling geometry. This would seem to imply leading with the heel. But.... this is really more the realm of the Stick bike, or a NoCom lowracer with the rider's feet way up in the air. DF riders sit butt behind the pedals and stick riders are feet above butt (sometimes way more than this 90 rotation); this is where the -10 comes from in ankling, the feet are forward slightly of the body so there is a backwards lean; just a little but enough that 0 to -10 degrees is implied. If we laid prone and road our bikes this would be pretty valid; as the feet go up this has to rotate more counter clockwise (there is a limiter on how far back is efficient, but that's another topic)
Next Drawing #3, below, is rotated 20 degrees forward for the V20 position (generalized). This rotation places the center of the power stroke right where John Tolhurst reported it should be, 65 degrees back from the 3 o'clock position, for a typical riders sized on at Cruzbike V20. This was discussed, a long time again and referenced more recently when we were first discussing Qrings about 2 years ago. John had blog post about it and a bunch of tech stuff published with drawings, but that info didn't make the transition from the old website to the new one.
Drawing #3 is about how mine looks with the stock seat and the medium chain stay; it's also how most of the Q-Ring photos appear in that thread and why most of us can use the same OCP setting. Under this assumption the heel should remain back 20 to 10 degrees from vertical during the power stroke. (this is the 0 to -10 degrees from drawing #2 rotated forward 20 degree)
So here are the observations:
(1) @LarryOz and @Eric Winn have stated they are pretty well pedaling with a vertical foot in the power stroke; they are also two of the tribe's (self acknowledged) short riders. On the medium chain stays configurations, which they ride; they will have higher feet than most people because they have to really shorten the boom to match their x-seams, they will be rotated to prefer a a vertical foot and it will be correct. Their rotation is closer to drawing #2 than drawing #3. This is also likely why Larry prefers a different OCP to most of us on his Q-rings. Different angles of attack and different rotations.
Lee what length chainstay to you have and what's your x-seam?
(2) Jason's longer legged, and has the thor seat. His position is somewhere between drawing 2 and 3 but I think a lot closer to #3 in most of the photos I've seen; (we don't have a definitive 90degree shot) Now go back and watch Jason's video. The angles are a little desceptive as they are shot behind the centerline. Notice how incredibly consistent his 20 degree angles are in the back-stroke relative to this rotation and you can see him ankling down about 10-15 degrees into the sweet spot, it is not vertical due to his fit on the bike. This is what I would expect given the record setting performances he has generated. If (a) Jason goes to a shorter crank arm and does not change his boom length, this will help his knees somewhat, and his foot angle will approach The 5-10 degrees range . I do not think he will be vertical, but it will head in that direction. If (b) he shortens his cranks and lengthens his boom his angle will stay about as it is and it will help open his knees even more. "B" is probably preferable to "A" but that my opinion that favors knee health over bringing more power from the hamstrings into the power game.
(3) Mine is almost exactly drawing number three with the stock seat and a medium chain-stay, and short cranks. I am not going to get a vertical push to match Larry and I should not try on my current setup as I would have to induce a lot of knee bend to get my boom that short. I have been contemplating going to a longer chain-stay to shift my rotation towards drawing #2 and a more straight on leg press push foot angle. Lengthening or Shortening the chain-stay is the only real way you can alter these angles by a large margin.
Ok so the take home points are: ?
- Boom angle / BB height relative to the 20 degree plan of the seat; will dictate how vertical the position of your foot should be for maximum efficiency.
- The higher the BB the more vertical your foot will point and how much you approached negative 10 degree in most cases.
- The lower the BB the more your toes are going to point.
- Just shortening the boom to get the foot vertical will not always work if it means you will drive your knee bending back to a point of greater than 90 degrees.
- Crank length has a minor effect on ankling depending on how you adjust for it, and is most useful to fix knee bend that is introduced trying to get the feet higher with a shorter boom.
- Chain-stay lengthen vs rider height is the number one limiter / lever for change.
- Unfortunately it is all connect and there is no 1 adjustment.
Lee I think you are correct about the angle of the foot relative to the centerline rotation; it matches the experts. But I think we have to consider centerline changing as the bike is adjusted to compensate for the limitation of the knee angles. Or in short I do not think vertical is a fixed reference point for us. Instead it is off set by the positioning of the butt relative to the BB height; and can sort of be generalized by referencing the seat angle for the sake of rough discussions, and find people a baseline for themselves.
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trapdoor2
Zen MBB Master
So...
What about Jason's "90 degree" position? Looks to me that it is well past 90 degrees. Not sure exactly what the reference frame is for that measurement but Miz Diane's knee therapist (she got new knees a year ago) uses a knee protractor. The therapist bases the angles on the bones (hip to knee to ankle). When I stop the video at full flex, Jason's bones are quite a bit past 90 degrees (I dunno, maybe 20 deg. past?).
What about Jason's "90 degree" position? Looks to me that it is well past 90 degrees. Not sure exactly what the reference frame is for that measurement but Miz Diane's knee therapist (she got new knees a year ago) uses a knee protractor. The therapist bases the angles on the bones (hip to knee to ankle). When I stop the video at full flex, Jason's bones are quite a bit past 90 degrees (I dunno, maybe 20 deg. past?).
ratz
Wielder of the Rubber Mallet
Prior to race not much he should do IMHO, maybe lengthen boom 5mm but no more
But now that he/we can see it; Borrowing Larry's crank oh tester is probably not a bad idea. One important thing to remember is on the stationary trainer the knee bend is always worse; as soon as you put the person on the road it lengthens out. Not sure why that is; but it's consistent; a shorter crank and maybe 5mm on the boom should fix it and protect the knees for the long haul.....
I'm sure Jason is loving us talking about him like he's not in the room.
trapdoor2
Zen MBB Master
I'm sure Jason is loving us talking about him like he's not in the room.
Ah, that's just the morphine talkin'.
Yah, I'm a firm believer in NOT making changes just before a race. I just wish I could follow my own advice.
Rick Youngblood
CarbonCraft Master
This would be my advice too. My opinion way too much bend on the back stroke and could get a little more straight on the outward stroke.
Again only my 2 penny's worth. I doubt you have any tears, but probably a little over stretched. It does look like a tight IT band causing pain in your collateral ligament being over stretched on the return stroke. A fairly common problem on recumbents with height bb's. The injury can come on slowly over time and then bam, makes itself known. This has had to me in the past with my left knee. The cure for me was going with short cranks. I'm now on 150mm, and haven't experienced knee pain in over a year. I have had luck with the KT tape supporting the strain.
I would recommend not racing through the pain, as the strain can heal much faster than a tear. You don't want a tear Jason.
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RojoRacing
Donut Powered Wise-guy
:lol I just noticed my new subcaption under my forum handle/name. I must have earned that last night
ratz
Wielder of the Rubber Mallet
:lol I just noticed my new subcaption under my forum handle/name. I must have earned that last night
super slim
Zen MBB Master
I WONDER who would have changed that!!!!:lol I just noticed my new subcaption under my forum handle/name. I must have earned that last night
