I dont get this analogy either. "Brakes" of vehicle have a specific and dedicated kinetic to heat conversion method, that enacted through the grip medium. Skiing uses the grip medium by placing it sideways to bring conflict of that grip in arresting the skier.
It would be akin to throwing a vehicle sideways and specifically not using the brakes to slow it down in ski terminology. A very different action to "braking" by your foot only. A far more committed and involved technique with approach attitude and placement of kinetic direction in how the body mass is used.
Obviously the feet transmit the directed desire to slow down, but that's the only tenuous connection as I view it.
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Anyway, snowHeads is much more fun if you do.
The stroke of the brake pedal is the flex stoke of the ski boot, the ankle moves down, plantar flexion on a brake pedal, opêrated by the sole of the foot, metatarsals, the ski boot does the same, however now the ankle joint dorsiflexes, moves up. The ankle joint absorbs and applies the energy against the resistence, the pedal on a car, the shin in your boot. A ski boot without progresive flex, would have the same effect if your brake pedal was replaced by a button, this stoke is what i'm refering to and what the test machine can give us information about. It's that resistence/flex though a stoke.
I sat down with the guys at Salomon yesterday to talk all this though, came up with this as a reply.
Do all ski boots undergo the same test, factory to factory, model to model. Yes
Do all ski boots given a flex rating the same flex the same? Yes, under test conditions, however in the shop and on the mountain and the person using them offer too many variables for the results to be consistent.
You're asking the wrong question. Each manufacturer will have multiple factories and of course they will standardise their flex specifications and testing across all their factories. The question for me is do all the manufacturers have exactly the same flex specifications and testing as each other? I suspect not.
Yes, in my experience they all do.
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Then you can post your own questions or snow reports...
Quote:
The ultimate test would be for Salomon to take a selection of their boot over to Atomic and put them on their test machine to see what rating they give. I suspect they would be in the right ballpark - you are not going to get a 130 boot giving a rating of 110 - but there would be a fair bit of variance. My guess (literally) would be in the range of 125 to 135.
Anything between 126 and 134 are given a 130 rating, so potentially you'd be testing a 126 vs a 134 and there would be a difference for sure. Thank god we don't have 121, 122, 123, 124 hey stock levels would be a nightmare.
After all it is free
After all it is free
Quote:
One thing I have I have learnt from these conversions is that it's not just about a customers weight, height, ability but also about their joint/ankle flexibility that would help to determine what sort of flex they would need/tolerate.
That's correct, but there is an order/heirachy to that also, the machine needs to move through a range of motion (ankle flex), certain energy is needed to move it there (weight) and the effect can be adjusted (tibal length). These are the variables that are static when testing but different at the shop. Temperature of the plastic effects it's resistance. This is why you feel the difference. As you change the test variables.
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CH2O wrote:
Quote:
The ultimate test would be for Salomon to take a selection of their boot over to Atomic and put them on their test machine to see what rating they give. I suspect they would be in the right ballpark - you are not going to get a 130 boot giving a rating of 110 - but there would be a fair bit of variance. My guess (literally) would be in the range of 125 to 135.
Anything between 126 and 134 are given a 130 rating, so potentially you'd be testing a 126 vs a 134 and there would be a difference for sure. Thank god we don't have 121, 122, 123, 124 hey stock levels would be a nightmare.
Well, quite.
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CH2O wrote:
The stroke of the brake pedal is the flex stoke of the ski boot, the ankle moves down, plantar flexion on a brake pedal, opêrated by the sole of the foot, metatarsals, the ski boot does the same, however now the ankle joint dorsiflexes, moves up. The ankle joint absorbs and applies the energy against the resistence, the pedal on a car, the shin in your boot. A ski boot without progresive flex, would have the same effect if your brake pedal was replaced by a button, this stoke is what i'm refering to and what the test machine can give us information about. It's that resistence/flex though a stoke.
The more you write the less sense it seems to make. The amount of braking you can perform with your skis is not directly related to the amount of pressure through your boot to the metatarsals, let alone the amount of flexion it does or does not give. There does not actually need to be any forward (i.e. flex-inducing) pressure through the boot at all.
This is nought but a tangent in this thread though, which as far as I can tell involves you repeatedly claiming that flex ratings are standardised across the industry, and everybody else saying that they're not. I'm reminded of Captain Rum
Rum: Opinion is divided on the subject.
Edmund: Oh, really? [starting to get the picture]
Rum: Yahs. All the other captains say it is; I say it isn’t.
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without any flex, as one compresses to absorb speed we would simply sit backwards and use only the tail of our skis to slow down., as the boots flex forwards we can compress both forwards and rearwards being better balanced and in more control of our braking.
And love to help out and answer questions and of course, read each other's snow reports.
And love to help out and answer questions and of course, read each other's snow reports.
Quote:
This is nought but a tangent in this thread though, which as far as I can tell involves you repeatedly claiming that flex ratings are standardised across the industry, and everybody else saying that they're not.
I don't believe i am listening to what anyone else says, i'm jyst relati,ng to my own experiences first hand that i've seen with my own eyes, if 10million Catholics want to tell me god exists i'll believe it when i see it.
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I have heard from the internet from a guy that the test does not relate to NM, only for him to send me a data sheet regards the flex of a particular boot where all the values were in NM, please tell me what i'm to believe?
You know it makes sense.
You know it makes sense.
Quote:
olderscot wrote:
Quote:
I sat down with the guys at Salomon yesterday to talk all this though, came up with this as a reply.
Do all ski boots undergo the same test, factory to factory, model to model. Yes
Do all ski boots given a flex rating the same flex the same? Yes, under test conditions, however in the shop and on the mountain and the person using them offer too many variables for the results to be consistent.
You're asking the wrong question. Each manufacturer will have multiple factories and of course they will standardise their flex specifications and testing across all their factories. The question for me is do all the manufacturers have exactly the same flex specifications and testing as each other? I suspect not.
Yes, in my experience they all do.
That's interesting if they do and worth getting confirmed by your industry contacts as it's at odds to what everybody has been saying up to now.
I seem to remember watching a video years ago where the testing results were converted via a table into different flex factors as obviously you need to convert whatever you're measuring at 23C into something comparable for the skier / boot fitter as to how the boot will perform on the snow and, as you say, different materials and designs will have very different behaviors at skiing temperatures than they will at 23C.
I'm still not sure we're getting the whole picture yet.
Otherwise you'll just go on seeing the one name:
Otherwise you'll just go on seeing the one name:
Yes the test is done at 23°C, it's the optimum for the properties of each of the plastics used so we can see how the flex of the boot changes over a lifespan of 30,000 flexes. From here we can work out the flex (resistence) of each boot through a ROM of 15° as an average, we can of course do a single isolated test, but here we have too many parameters that would make any kind of liner flex comparison impossible.
Poster: A snowHead
Poster: A snowHead
Yes, but different boots made from different materials measured in NM at 23C will have very different flexes at skiing temperatures. So somehow, whatever, they're measuring at 23C has to 'Converted' using some proprietary calculation to their own 'flex' rating for it be anywhere reasonable.
Also this video from Atomic says their boot flex machine is custom made and if I look at the chart it's measuring from 5 - 32 degrees which doesn't match up with what you're being told.
absolutely there are different temperature effects on different plastics, however each plastic can be modified to perform equally at the same temperature. so far, excluding Head and Fischer, i have watched each machine, test boots. I have asked plenty of questions when stood next to these machines and what they do. They can be used for many reasons. One of those reasons can be to deturmine the resistence of the boot as it moves through a stoke. This test is done at 23°C, all of the manufacturers do this test, under the same conditions to get that resistence figure, that figure is how they attribute the flex number of your boots.
Well, the person's real but it's just a made up name, see?
Well, the person's real but it's just a made up name, see?
yes the machines are custom made, but do the same job, you can use different tuning forks to get a pitch, they don't have to be identical to give you the precise same pitch
the video is perfect, you can see the bespoke design, but all companies have these machines for the same reason, nobody has one made of bamboo for shits and giggles.
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of course they test at different temperatures, -32 for example would to be test the glass effect (TG) and breakage. But to get the number you buy, they test at 23°C
That's Matt's voice from Atomic, saying they are measuring NM, on the blister podcast he says they don't relate to NM, the same guy saying two different things, no wonder you're all so confused, it's really frustrating.
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Then you can post your own questions or snow reports...
If I look at the chart in the Atomic video it looks as if the machine might be set to move +17 degrees to -10.44 degrees with the chart showing there being zero load at +15 degrees.
But here's the thing. All the manufacturers are probably doing similar tests, using similar machines but if one is doing +15 to -8 degrees and another is doing +17 to -10.44 degrees then the results are not standardised and not comparable. And then you have to add in the different calculations for materials and design to 'Attribute' each result to a nominal flex rating that will mean something in practical use and the net result is that the flex ratings are not standardised across the industry. They will be similar but they will be different.
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After all it is free
totally agree, there are so many variables, however whilst the machines can be configured differently, the numbers you get are from the same set of conditions. Every company measures other's boots too. The point that needs to be taken in this whole discussion is that the differences observed are not to be attributed to different brands, but to different models, two tecnica boots, when tested outside the controlled enviroment will flex as differently as two from two different manufacturers. If you don't, and you can't test different boots under the exact same conditions you cannot get the same results. To say a Salomon 130 is different to a tecnica 130 while possibly correct, you are not testing under the same conditions, forget all other variables, the boots are not the same volume, so cannot flex the same, so you will feel a difference, despite both manufacturers testing the same, identically, you are not.
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I don't think we're in the same place yet.
The way I see it, the flex rating is just a number assigned by the manufacturer to give people an idea of how the boot will behave on the skiers foot. There is no standard (which means an agreed common specification) for the measurements they're doing ( not just that they're doing something similar) and there is no standard to convert that measurement to a flex rating. The different manufacturers will try to have the flex ratings mean similar things but I've not seen anything yet that suggests they are standardised.
In other words, they are not testing the same, identically. There are differences in what they're doing.
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I think at least we're getting closer to understanding how the manufacturers seriously test their boots before attributing flex ratings. It's not just a stupid number plucked out of the sky and slapped on boots. That the testing is uniform, and whilst there's no standards agency, setting plastic hardness, type, colour, density that the industry tests, and tests and tests.
We have a simple formula at our shop to find your flex rating, double your weight in KG, add 10 if you're a dynamic skier, add 10 if your tibia length is above average compared to foot length. Few grown adults leave with anything below 120 flex. Seems to work out for the last 10,000 or so of our last clients!
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@olderscot, again, whatever you've heard, i've stood with the dudes who's job is it to do these tests, from all brands, they're doing the same tests under the same conditions, i can't un-see what i've seen. They all want to run a standard test, there's no cheating going on. What do you need to be standardised more? The temperature is the same, the amount of flexes the same, the ROM the same.
And love to help out and answer questions and of course, read each other's snow reports.
And love to help out and answer questions and of course, read each other's snow reports.
CH2O wrote:
We have a simple formula at our shop to find your flex rating, double your weight in KG, add 10 if you're a dynamic skier, add 10 if your tibia length is above average compared to foot length. Few grown adults leave with anything below 120 flex.
so if you are a 100kg dynamic skier with long legs you should be in a 220 flex boot ?
So if you're just off somewhere snowy come back and post a snow report of your own and we'll all love you very much
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So we're starting to see something here, the identical same boots made from different materials will have a different result, a lower or higher flex. Hense 80-90-100-120 etc
Now for me at least this is why i right off all boots lower than 100, the results are because of the materials, and as a bootfitter and as a skier this has massive effects on me day to day.
If my boot is say 80, it's made of PolyPropylene. The stuff shampoo bottles are made of. Its data sheet suggests it's not great when taken below 0° the TG rating, Glass effect is really high, essentially it gets super stiff fairly quickly as we go below 0 degrees c. It's said the beginner skier that needs the 80 flex boot skis for a maximum of 3 weeks a year, possibly school holidays, Jan, Feb, April, three very different times of the year to ski at different temperatures. -15, -5, +5, are the averages during these times. Her polypropelyne boots are stiffer at differnt holidays and therefore the first couple of adaptive days are weird cos the boots don't work consisently each time she uses them. A stiffer plastic would be more stable and consistent.......
You know it makes sense.
You know it makes sense.
Quote:
so if you are a 100kg dynamic skier with long legs you should be in a 220 flex boot ?
Scientifically speaking you do yes, if travelling at 20kms
Otherwise you'll just go on seeing the one name:
Otherwise you'll just go on seeing the one name:
@skimottaret, Don't worry, your boots are around 450/500 flex when you're using them, plus you'll be stopping from faster than 20kms i hope, if not, better just walking me reckons.....
Poster: A snowHead
Poster: A snowHead
most of your boots are around 500flex when you use them, all of you!!!!
Obviously A snowHead isn't a real person
Obviously A snowHead isn't a real person
At minus 15C your boots flex, excluding ankle flex and volume variables.
70 (PP) X7 490NM
80 (PP) X6 480NM
90 (PU)EST x5 450NM
100 (PU) EST x5 500NM
110 (PU) ETH X4
120 x4
130 x4
130+ and Amides X3
Well, the person's real but it's just a made up name, see?
Well, the person's real but it's just a made up name, see?
So temperature is the greatest variable when we look at ski boot testing, it's done at 23°, most of you try them on at room temperature in a shop, then at at least -5° average when skiing. The hardening of plastic effects the vector angle of the flex pattern of the boots hugely. As well as making the plastic more difficult to bend. This is most obvious at the lower flex spectrum, the boots made of PP, and they are generally all the highest volumle shells also, it's a horrible combination.
So if each of the manufacturers get this box at the right temperature, the biggest variable is taken care off, and we can move on to the amount of times we flex the boot, how far, and from what height. We can start building our own machine.
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Their devices have to be able to work ultra precisely accros many variables, they need to get WC ski boots just right, right flex, right temperature, average speed, this same machine enables them to do it, it's no basic litmus test.
Their devices have to be able to work ultra precisely accros many variables, they need to get WC ski boots just right, right flex, right temperature, average speed, this same machine enables them to do it, it's no basic litmus test.
The key points I'm taking away from this are:
1. You keep saying it's a standard test yet I've shown you video evidence of Atomic doing a test that is different to what you say it is. Different means not standard. You can repeat your belief as much as you want but how about you get your contacts in different manufacturers to share the test specifications? If it is standardised why would they not want to share it?
2. The measuring machines are ultra precise but there's clearly some tolerance allowed within the results but the key thing for me is that these tests are being done at 23C so don't reflect well on performance on the slopes. That makes the performance on the slopes approximate rather than anything precise because the different materials change differently at different temperatures. Here are some example from your own data:
100 (PU) EST x5 500NM
110 (PU) ETH X4
So a 100 flex boot in (PU) EST will be 500NM according to you at -15C whereas the 110 flex boot in (PU) ETH will be 440NM. Where's the logic in that. It just confirms that the flex rating is an approximation to how it will perform in real life, not anything hugely accurate.
3. You keep seeming to want to make huge leaps from this to try and use the flex rating rating to calculate how much strain will be put on the achilles heel, how much force is needed for braking from what speed (?), to build your own device to measure the flex. I think you're getting too carried away with this and trying to use the flex rating for all kinds of things rather than just using it for its intended purpose. As a simple guide to the stiffness of the boot to help people choose an appropriate ski boot.
Then you can post your own questions or snow reports...
Then you can post your own questions or snow reports...
Quote:
1. You keep saying it's a standard test yet I've shown you video evidence of Atomic doing a test that is different to what you say it is. Different means not standard. You can repeat your belief as much as you want but how about you get your contacts in different manufacturers to share the test specifications? If it is standardised why would they not want to share it?
No you've shown me 1 manufacturer doing a test, you have assumed they all do it differently, and that the machine is set up for the video to test the resistance, not another measurement.
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2. The measuring machines are ultra precise but there's clearly some tolerance allowed within the results but the key thing for me is that these tests are being done at 23C so don't reflect well on performance on the slopes. That makes the performance on the slopes approximate rather than anything precise because the different materials change differently at different temperatures. Here are some example from your own data:
The machines do more than just attribute restisence in NM, that is why they're are so many variables on show. 23°c is the temperature when all the properties of each plastic are best on display, for this reason we conduct the test at 23°, temperature is just one variable and the most important.
Quote:
So a 100 flex boot in (PU) EST will be 500NM according to you at -15C whereas the 110 flex boot in (PU) ETH will be 440NM. Where's the logic in that. It just confirms that the flex rating is an approximation to how it will perform in real life, not anything hugely accurate.
Indeed, what is the logic, to offer a product at different price points, however these plastics change at differnt temperatures, i have given you approximate multiplying factors at Minus 15C, to be accurate we would need actual polymer data, injection temperatures, setting hardness etc, that information is indeed kept and i've not every had access, it will be unique to every boot, at different days, that's just how these things are. However we could build a mchine and test it. Using the same variables as the manufacturers do.
Quote:
3. You keep seeming to want to make huge leaps from this to try and use the flex rating rating to calculate how much strain will be put on the achilles heel, how much force is needed for braking from what speed (?), to build your own device to measure the flex. I think you're getting too carried away with this and trying to use the flex rating for all kinds of things rather than just using it for its intended purpose. As a simple guide to the stiffness of the boot to help people choose an appropriate ski boot.
No, no, you're miles off i'm afraid.
After all it is free
After all it is free
Quote:
No, no, you're miles off i'm afraid.
Well, that's your opinion but I've not heard anything from you to convince me otherwise, so I remain unconvinced that you really know what you're taking about.
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Excellent, so in summary each boot is give some arbitrary number in and around 100 based on it being close to some other arbitrary number from some other company in the hope it will all be ok at some point.
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Not the words I would use but that's probably not that far off. You keep talking about Newton Meters even though you say they've told you the flex rating is not Newton Meters but is the energy used over the boot flex cycle.
So, here's a challenge for you. If a boot is given a flex rating of 130 what does that mean, what is the formula used in the calculation and what are the units?
If you can't answer that then you really don't have a clue.
FAQ
Poster: A snowHead
