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Boot ramp

post #1 of 15
Thread Starter 
So I've read plenty of of the threads about ramp angle in here and I have found that my personal correct ramp angle should be 3 degrees using the triangle method http://forums.epicski.com/showthread...=48893&page=3. My current boot (Atomic RT CS 130, size 25.5) and binding (Rossignol FKS) setup has the total ramp angle 7.5 degrees. I calculated the required toe lift and the result was 16mm !!! It will be technically possible to lift the binding toe piece BUT do you see it appropriate?
Any advice is highly appreciated because the closest boot specialists are located more than 500 miles far-away.
post #2 of 15
Thread Starter 
Sorry for the bad link, here is the correct one http://forums.epicski.com/showthread.php?t=48893&page=3
post #3 of 15
Rather than relying on calculations that may or may not be relevant to you, I would suggest that you get someone knowledgeable to watch you ski. Then do some testing of small increments of toe lift (under the binding), i.e. 2mm at a time. Test on hard snow, carved turns, with decent speed & rhythm. Take video before and after.

Hope that helps.

post #4 of 15
Thread Starter 
Many thanks for the response, but let me try to ask the same question the other way. You certainly know that the Rossignol FKS has one of highest delta - about 10mm toe heel difference. The boots zeppa is somewhere between 4 to 5 degrees. I've read in other thread that ANY ramp angle higher than 4 degrees requires modification. If this was true wouldn’t be increasing only by 2mm steps too conservative approach? In my case 3mm lift equals to only 1degrre change. Am I absolutely wrong that starting with at least flat binding position would be better?
I do apologise for stupid questions but after reading how much either the flat or slightly higher toe to heel binding position improved someone’s skiing performance I would like to benefit from that “miracle” too.
post #5 of 15
I would disagree with any generalization about this or that zeppa angle.

Why don't you keep it simple and ski on a binding with less delta (i.e. Atomic 6.14 or 10.18) and see how that goes?

2-3mm at a time is a reasonable approach at speed on hard snow. You will feel the difference. If you don't, then the delta/zeppa angle issue is not your primary concern .

Hope that helps.

post #6 of 15
I agree with Matt. It would be very difficult to assess your needs based on what worked well for someone else's needs.

There is not a magic set-up that will give every or any skier the same results on snow. Try to refer to some of the Ramp angle/Binding delta threads that talk about how to do quick tests on snow by increasing and decreasing the binding ramp angle temporarily to see where you need to go for your skiing and equipment set-up.

post #7 of 15
Thread Starter 
Unfortunately the skiing season has already finished in our country. I have just bought new pair of Rossignol race stock skies (model 2005/06) and I wanted to set up them before new winter season. There are not many instructions available and I hoped that the “triangle” method was the proven and easy to use tool for everybody. I certainly agree that the on snow testing should be the final evaluation but what about the initial set up? Are there any broadly acceptable rules that will enable to set up the foot-boot-binding-ski system at home before the first skiing?
post #8 of 15
Perhaps a little clarification will help you better understand Matt's and Jim's opinions. I don't want to speak for them but will explain the strengths and weaknesses of the triangle method.

The human body is simply a machine. All the engineering principles and formulas that are used to calculate torque, forces, etc in a machine are absolutely applicable to the human body.

The triangle method pioneered by David MacPhail simply relies on the basic math to determine at what ramp angle your centre of mass (COM) would move beyond your fulcrum (Toes/ball of foot) at which point we begin exploring something we humans try to avoid. TIPOVER!

David's method is absolutely spot on, correct use of the math. However it cannot be used as absolute because the formulas can't take into account your natural tendencies or preferences, the fact that your COM may not be where we think it is, etc. It also does not take into account the effect of wearing ski boots. It is instead fundamental trig.

For example when ramp angle is decreased, effective ski boot stiffness is increased. Perhaps that doesn't work for you with your boots. I could go on but if you understand the math from the calculations you can work out more examples for yourself. In short, the problem with relying solely on the calculations is that they miss the effects of being human and being engaged in a movement activity that is also affected by the equipment.

That said, David's contribution was substantial and definitely underappreciated.

Now to your problem. I agree that 7 degrees is too much for most recreational skiers. I have measured as high as 9 degrees which is outrageous. However, your goal should not be to get to three. It should be to get to what works best for you in your situation. As Matt and Jim said.

2-3 mm is absolutely something you should feel. Why hurry the tests? Go slowly and learn along the way. Regarding the 16mm need; it is possible to get close or even all the way there if necessary. Remember that lift under the toes of the boots works identically to lift under the binding toe and lift removed from under the binding heel.

I believe if you remove your heel you will find an approximately 5mm spacer there that can be removed. It is also possible to put 5mm under your boot toe and more under the binding toe. As you can see we are getting close.

Just go slowly as Matt and Jim recommended. There is no hurry to get it done and David's work because we are human and not simply machines is not absolute.

post #9 of 15
David did develope hard data in his research with the birdcage. He developed his simple math to help people get close to their optimum ramp out of the starting gate. He used his hard date to substantiate his math.

What his hard date suggested was that there was far less ramp angle need differences from person to person than what many thought, and what many in the industry were setting people up on. Ramp is only one piece of the puzzle though. David was adamant about using bindings with no height difference from heel to toe. Among other things.

Why not use the math as a starting point fro ramp angle and work from there? The few who I know who have tried this method have found success.
post #10 of 15
Thread Starter 
I am in doubt now. I really like the idea to start with math and work from there. On the other hand the boot specialists are advocating the slower way.
I must think it over from the manufacturing and installation point of view too because the lift under the binding toe is my preferred option. The easier way will probably win.
post #11 of 15
David's work is thought provoking, but it is not a rigid recipe for everyone. Furthermore, you won't find too many world cup athletes with flat ramps and minimal forward lean angles - and that's also something to think about.

The math cannot predict the vagaries of your individual biomechanics, nor can it accurately model all the other factors involved in fore/aft balance in a dynamic situation.

So... you can dork out with a slide rule & calculator, or you can do some practical testing on hill until you find the sweet spot for you.

Regards ,
post #12 of 15
Actually David did fit boots for a number of successful WC athletes back in the day as well as with help designing for ski boot manufacturers, and research for sport shoe manufactures. But that's a conversation for another forum. Jarda it will be interesting to see how close the ramp turns out to your calculations.
post #13 of 15
The reason there is testing outside of research facilities is because as Matt and I have mentioned although the calculations can be used to determine many things in humans there are still individual preferences are circumstances that make each person an individual.

Testing will always be the final word.

When I helped with research on binding position for Atomic I had long discussions with Atomic head of ski design. When asked how they determined binding position for their WC athletes he replied "We mount them ball-of-foot/centre-of-running-surface and then they test from there."

Same for you! Go test.

post #14 of 15
Thread Starter 
Thanks for mentioning the fore/aft binding position too. I am really glad that at least this point seems to be clear. This is definitely the first modification I am planing to do because it’s relatively very easy.
There is one thing that makes me hesitant to rely only on snow testing. I am used to ski on many different skies and I feel I can very quickly accommodate my balancing skills to any ski and any binding setup. On the other hand – I have never ever played with changing of the binding setup and comparison of the immediate results on the same ski. I am sure that it is worth spending some time and effort but as I stated sooner I would like to start from the best position achievable at home.
post #15 of 15
How you go about doing this is really up to you. But the advice from everyone that has answered is to test.

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