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lonbordin

Ankle Hinge

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Boots...  ah boots.

So I've been riding this season in my UPZs.  I've been trying to pay more attention to my body's attempts to give feedback.   

I fit in these shells but it's tight... aka .5 finger or race fit.   My rear ankle is talking a little more early this season.  A little soreness and I'm listening. 

I was going over my boots making certain everything is tight, etc and I realized that my ankle's pivot point isn't close to the boots hinge.

My assumption is that this is proper:

rVl1pxU_d.jpg?maxwidth=1920&shape=thumb&

My ankle pivot would be in the center of the blue dot in the following photo:

QQBzIum.jpg?maxwidth=1920&shape=thumb&fi

I wondered if I moved the pivot would that be possible.  It appears not, would create a host of other problems as seen in this photo:

fh3nv0W.jpg?maxwidth=1920&shape=thumb&fi

In the course of all this I grabbed a few other boots I have lying around and did some measurements (all are approximate).

First measuring from the floor (unweighted) the center of my ankle pivot is ~109 mm from the floor and ~80 mm from my heel.

Deeluxe Track 425 Hinge is Adjustable 110 max and 78 mm from the boot cup where your heel would press against
UPZ 83 mm high and 75 mm from heel
Backland 75 mm high and 60 from heel
Lange 130 Dual Core (Ski boots) 83 mm high and 67 mm from heel

The astute reader would be correct to point out that I don't wear these without liners and footbeds which further lift my foot and push it forward making it so my ankle is where the blue dot is in the first photo. 

We talk all the time on the forum (and other forums that speak hardbooots/skiboots about width, toebox shape and heel hold.  I've never read anything that really discusses ankle pivot placement (I'd be happy to so post your sources!).

How badly am I f*cking up with riding with such a difference in ankle and pivot?
Maybe it's no big deal and I'm not seeing the geometry that will allow me to sleep tonight...

Thanks for the input!

Mahalo- Dave

 

Edited by lonbordin
flipped the links...

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9 minutes ago, SunSurfer said:

@lonbordin where on the x-ray is the painful point? Is the pain on one side, both sides, in the middle, all the way through?

I have general soreness stretching from the inside ankle pivot point across the front of the joint ending just before the outer ankle pivot point.  Maybe even a slight swelling from the long day.  More like a band of soreness maybe a few cms wide and more my rear ankle than my front.  I did fracture the end of my medial malleolus two seasons ago and there are two screws holding all that together.  That said I've had no pain/soreness from the area while working out (long hikes, skating, etc) the past year.

@SunSurfer thanks for unearthing that x-ray photo!

Edited by lonbordin

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Does the pain feel like it's from the joint surfaces itself or more from the flesh in front of the joint? When I read your description above it seemed more like the flesh rather than the joint. 

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Just now, SunSurfer said:

Does the pain feel like it's from the joint surfaces itself or more from the flesh in front of the joint? When I read your description above it seemed more like the flesh rather than the joint. 

Maybe a little of both? Sorry the pain was Thursday evening and while I did note it I had much to do (packing, Dad stuff, etc) so it's a distant memory.

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My thinking is that the pivot point for the hinge is unlikely to be a cause, and unable to be altered.

Fixes may lie with the position of the 3rd strap/buckle, maybe the liner, and maybe with the adjustment of the spring system. Something(s) putting undue focal pressure on that part of your foot/ ankle.

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10 hours ago, lonbordin said:

We talk all the time on the forum (and other forums that speak hardbooots/skiboots about width, toebox shape and heel hold.  I've never read anything that really discusses ankle pivot placement (I'd be happy to so post your sources!).

How badly am I f*cking up with riding with such a difference in ankle and pivot?
Maybe it's no big deal and I'm not seeing the geometry that will allow me to sleep tonight...

I've relocated the ankle rivets on most of my boots. This pays off, assuming you want to ride 'out of your feet'.

Given the other challenges posed by typical boot geometry, allowing for a more transparent flex at the cuff doesn't seem a priority, and therefore isn't worthy of discussion.

Similarly, many, (probably most) riders use the front of the boot as a lever. If the manufacturers located the rivets in the 'correct' location, the boot would then be criticized for being 'too soft'. 

As noted, you don't have much plastic to work with if  you simply move the cuff up and forward.

You could, however, experiment by leaving the cuff at it's intended height on the scafo, but drilling new pivot locations up and forward, depending on what the plastic will allow.  Use generic hardware store T nuts, and trim the prongs so they don't go all the way through the lower shell. If you don't like what you get, just push them out and slap some tape over the holes for slush season.

You may need to remove the originals for clearance.

If you opt for this butchery, use the inner ankle bone as your reference point, and mirror the outer pivot location to match. Otherwise you'll have asymmetric flex.

Won't be ideal, but you may find it a lotbetter than what you have.

You will, however, run into a sliding friction conflict with the forward lean band, as that anchor point is located to work in harmony with the original ankle pivot location.  As an adult, you'll probably be safe taking a few runs for proof of concept with that assembly fully disabled, after which you may choose to build/buy a suitable replacement.

 

As to the ankle pain, odds are good its a matter of sustained load at full flexure. While your other activities involve range of motion, they load the joint within 'intended' parameters.

Typical hardbooting goes beyond in that respect.

That it wasn't noticeable previously probably has something to do with age/injury/etc.

 

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Hey Dave,

Several years ago I was told that one of the things many racers preferred about the original North Slopes boots was that the ankle pivot point was in a better location, anatomically speaking. I don't know more details.

I did bring this up in a thread here when the new Mountain Slope boots came out and @Puhutes confirmed it. I'll try to find the thread.

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3 hours ago, bigwavedave said:

new Mountain Slope boots 

 @Beckmann AG  I recall you have just had a pair on the cobblers anvil?

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i do wonder why it is placed so out of alignment from the ankles natural pivot point, if it was merely stiffness wouldn't you just beef up the tongues across your range of boots 😕

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5 hours ago, bigwavedave said:

Hey Dave,

Several years ago I was told that one of the things many racers preferred about the original North Slopes boots was that the ankle pivot point was in a better location, anatomically speaking.

@Puhutes

I had thought the location and angle of the strap across the front of the ankle joint on the Northwave made for better heel hold down. I have modified Head Stratos and UPZ boots to achieve approx. the same angle and had better heel hold down as a result. 

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I'm reminded of Alice's conversation with the Cheshire cat in "Alice in Wonderland". Alice asks which road to take but doesn't know where she is going.

The first step to solving the pain problem is working out what you think is causing it. Only then can you come up with a remedy for the identified cause. Examine the evidence you have, make an hypothesis about what the evidence means, and then try and solve the hypothesis problem.

If you don't have an educated guess of the cause, just trying different things just generates white noise in the process of identifying and fixing the problem.

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1 hour ago, SunSurfer said:

I had thought the location and angle of the strap across the front of the ankle joint on the Northwave made for better heel hold down. I have modified Head Stratos and UPZ boots to achieve approx. the same angle and had better heel hold down as a result. 

The ankle pivot feature was pointed out to me (among other attributes) by a Canadian coach that had been hoarding and rebuilding Northwaves a few years back, when the Mountain Slope was just a rumour. It was in response to my asking, "what's the deal with all the old yellow boots?", while standing on the side of a NorAm race course at Buck.

Another thing he said was that the plastic has a more consistent stiffness in variable temps compared to other boots. Don't recall any mention of strap locations.

Regardless, Dave's first post above sparked my memory of this conversation. Seemed relevant and It might be interesting to see if someone wants to go down that rabbit hole and measure various boots.

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Pain issues aside, @lonbordin, your pivot point looks off.  The joint slides around that radius on the foot bones.  Yeah, yeah, I don't know the bone names, but I recognize a hinge when I see one!  

 

rVl1pxU_d.jpg

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32 minutes ago, Corey said:

Yeah, yeah, I don't know the bone names, but I recognize a hinge when I see one!

Me neither but the real problem appears to be all that metal left behind by your orthopedic surgeon. You should probably have that cleaned up before messing about with small stuff like pivot points...

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2 hours ago, SunSurfer said:

The first step to solving the pain problem is working out what you think is causing it. Only then can you come up with a remedy for the identified cause. Examine the evidence you have, make an hypothesis about what the evidence means, and then try and solve the hypothesis problem.

If you don't have an educated guess of the cause, just trying different things just generates white noise in the process of identifying and fixing the problem.

My input, the shell-tongue are to soft and aren't keeping pressure properly off your surgically installed pins, which have no ability to absorb another solid object.

3 hours ago, SunSurfer said:

I had thought the location and angle of the strap across the front of the ankle joint on the Northwave made for better heel hold down. I have modified Head Stratos and UPZ boots to achieve approx. the same angle and had better heel hold down as a result. 

Yes, reading this thread, northwave was the first and so far best way to answer a vexing problem.

And luckily, there's a reboot. 

Edited by ursle

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@bigwavedave Agree with the points about the pivot point and the type of plastic in the Northwaves, and there are other things about the design that make the heel hold and movement control excellent.

Reading the OP's description of the pain makes me think that the amount of forward flex being created while riding may be creating the pressure point. That might be due to the liner compressing or pressure from the strap across the front of the ankle.

 

Edited by SunSurfer

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Watch the video to see where the centre of the rotation movement is when the ankle moves and the upper curved surface of the talus slides underneath the tibia and fibula. The pivot in the UPZs might be better matched to where the rotation occurs than you thought.

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First I want to thank everyone for their input, much appreciated!

@Beckmann AG  I’m leaning toward experimenting a bit.  I’m going to go down and see how much distance I can gain after I make this post.

@bigwavedave  I looked the the NW site… the pivot does seem much higher than other boots… I wonder if someone on the forum has a D size shell that can take a couple of measurements. I've asked in the 951 thread. Those are some pricey boots!

@SunSurfer  I get the hypothesis testing…. Unfortunately I’m not double-blind to the experiment and like all of us I have my biases.  My current hypothesis is that having such a difference between pivot point of boot and pivot point of ankle is not optimal.  Looking at the video convinces me even more that pushing all my weight on two separate pivot points means I’m creating forces between those two points.  I can’t conceive of that being optimal.

@scottishsurfer  I'm guessing the pivot is probably in line for 70% of the population... I'm just several significant digits outside of normal.

@ursle The two small screws come from underneath and only are in the end of my medial malleolus… they don’t receive pressure from the side of the shell and certainly not from the tongue.  I’ve had a couple of impacts in that area and the feeling is very different.

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3 hours ago, Corey said:

Pain issues aside, @lonbordin, your pivot point looks off.  The joint slides around that radius on the foot bones.  Yeah, yeah, I don't know the bone names, but I recognize a hinge when I see one!  

 

rVl1pxU_d.jpg

@Corey there is a parallax error in the image created by the point from which the x-ray is taken. With x-rays the image is formed by transmission through the object to the receiver behind the object. Generally the distance between the point x-ray source and the receiver is quite short so that the edges of the image will appear misaligned while the centre of the image is correctly aligned. Objects further away from the receiver appear magnified in the image. Understanding this is key to understanding the alignment of the square ankle pivot nuts in the x-ray.

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I'm just pointing out that the ankle pivot point isn't as far up and forward as indicated by the blue dot above. i.e. I ignored the boot and looked at the bone radius. 

Interesting on the parallax error though. Kind of a 'fisheye' effect of a nearby point source and being able to see through the subject. 

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Ok lets get a cadaver foot in the boot with buckles removed and run it through the band saw and get this settled.

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9 hours ago, Lurch said:

I recall you have just had a pair on the cobblers anvil?

Are you surveilling my operation? Or simply making the reasonable assumption that I own a pair of cobblers anvils?

@lonbordin Rumor has it you might be in the neighborhood later this month.  Stop in at the shop If you want to bring heavy machinery to bear on the problem.

I could set you up with the wheel and planishing hammer if you want to custom form a cuff, or whatnot. 

7 hours ago, scottishsurfer said:

i do wonder why it is placed so out of alignment from the ankles natural pivot point, if it was merely stiffness wouldn't you just beef up the tongues across your range of boots

There are many considerations that go into boot design. Logic/reason doesn't figure near the top of the list.

E.g., modern telemark boots won't really allow one to make a proper telemark turn. They will, however, fulfill the expectations of skiers who never learned how to make a proper telemark turn.

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23 minutes ago, Corey said:

I'm just pointing out that the ankle pivot point isn't as far up and forward as indicated by the blue dot above. i.e. I ignored the boot and looked at the bone radius. 

@Corey Maybe I didn't make it clear. The X-ray is not me, that image is for illustrative purposes of what I think is correct.  

The blue dot is where my ankle joint is in my UPZs.

8 minutes ago, Beckmann AG said:

 Rumor has it you might be in the neighborhood later this month.  Stop in at the shop If you want to bring heavy machinery to bear on the problem

That's a liberal use of neighborhood. 😆

I'd like to stop by and split some wood.  I'll send you a PM and we can talk availability.

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