MORE ON ZEPPA (BOOT BOARD) RAMP ANGLE


Slowly, but definitely, the ski community are learning the positive boot board (zeppa) ramp in many boots is excessive and not beneficial to many of us. Excessive seems to be anything over approximately 3.0 degrees. The lowest ramp I have measured to date was 2.4 degrees in the latest Dalbello DRS boot in a Mondo 27. A size 23 is still over three degrees.

I believe most manufacturers have too much ramp in their boots. As explained in a recent post, the problem is worse for smaller boots, since as boots shorten, ramp increases. Still, even if boot ramp is correct, we should wonder if binding designers think boot designers need some design help, since nearly all bindings have positive ramp (delta) of at least a few degrees for Mondo 27 boots.

Like boot zeppas, as binding toe and heel are mounted closer together, delta increases and is additive with boot ramp. Further, there are additional changes to boot angle since binding delta tilts the entire boot, It also alters effective forward lean.

I believe when we demo skis, a portion and perhaps a substantial portion, of the differences we feel between skis, may be accounted for by the differences between ski binding ramp angles. At the very least, binding angles can corrupt on-snow testing of skis and/or boots. If you are working to get your boot setup perfectly adjusted to your preferences, why allow binding ramp variables to alter an optimal configuration?

In my opinion, the best solution is a 0 degree binding delta. If this is not achievable, at least set all skis bindings to the same delta. This may be easily, achievable. Most manufacturers make shim kits for at least some of their bindings. Shims appear to be available for most bindings used on race skis that allow incremental changes to 0 degrees delta. However, not all shops know of the existence of these shims since  kits are usually in the race catalogue, not the recreational product catalogue.

If alterations to either binding heel or toe height are made, an equal change must be made to screw length or there will definitely be an unsafe situation. Binding holes are between 8.5 and 9.0mm deep. Be certain screw threads do not extend more than that amount from the bottom of the binding.

One last thing to remember is that moving binding position forward or backward on the ski could subtly alter binding delta since the top surface of skis are crowned. Moving the bindings to a new position on the crown will affect the height of the heel and toe. If bindings are moved after setting binding delta, it should be checked again.

I always prefer to direct measure rather than use a calliper and calculate zeppa or delta. The photos below show a device I had fabricated that allows the angle of a zeppa to be measured between the two primary load points under the heel and the head of the first metatarsa (aka ball of the foot). The distance between the rods can be adjusted to these two points on a zeppa or to the 2 points of contact of a boot sole on the heel and toe pieces of a binding.

img_0739

The SmartTool digital level shown in the photo below accurately reads to one decimal place.

img_0743

The SmartLevel is too long to sit properly on a zeppa. The two rods of the frame that supports the level lets me avoid toe kick or any other shapes that can distort ramp angle.  I just measure the angle directly between the two points of support.


Lou Rosenfeld has an MSc. in Mechanical Engineering with Specialization in Biomechanics earned at the University of Calgary Human Performance Laboratory. His research was titled, “Are Foot Orthotic Caused Gait Changes Permanent”.

While at HPL, he assisted with research on the effects of binding position for Atomic, and later conducted research for Nordica that compared Campbell Balancer established binding position to the Nordica factory recommended binding position.

Lou is one of the invited boot-fitters on the EpicSki forum “Ask the Boot Guys” and has authored articles on boot fit, balance, alignment and binding position for Ski Canada, Ski PressSuper G, Calgary Herald, and Ski Racing, USA. He is a CSIA Level 2 instructor and CSCF Level 1 coach. He currently resides in Calgary where he owns and operates Lou’s Performance Centre. A selection of his articles may be found at www.Lous.ca.

 

3 comments

  1. Has anyone checked Atomic bindings? A few that I have worked with over the years were zero delta as far as the height of the AFD on the toe piece and the surface height the heel rests upon. Then the only issue becomes how it is mounted on the ski in relation to the ‘hump’ in the middle of the ski. I’ve always felt that the act of moving the binding forward of the mounting point was more of the effect of changing the delta angle than relation to the fore/aft position because as David reports and from my own experience fractional changes of net ramp are huge in effecting performance. I at one time played with those two factors and that was my un-scientific conclusion. Haven’t touched that in years though, do have a pair of K2 Kung Fujas that have multiple mounting points, hard to guess which one to use!! As in everything, common ‘farmer’ sense is the best solution to these issues; I simply collect screws from old bindings, make sure they go to the same depth as the old ones and try to keep them from coming out the bottom unless I want a pair of ‘slow’ skis. I’ve been rearranging my own bindings for years. I bought a pair of used skis from a friend who happens to be a master ski tuner. I let him keep the bindings because I have my own prejudices and when I went to mount mine, I felt that the toe piece holes were off center. I used an adjustable square which confirmed that indeed they were about 1/8″ off center. The other ski; same story, both were perfectly off the same amount. What my conclusion was that it couldn’t be the techs error, it had to be the jig was off center so everyone’s skis mounted with that jig were off center by that amount for who knows how long, if it was built wrong or got dropped, whatever. I measure the screw, add the thickness of the shim and use that length screw for the new setup. How many times do you see a skier with an inch of ice or snow somehow click into their binding and ski off? I try to enlighten them on the situation but I know as careful as I try to be that I get a layer of ice or whatnot in between the boot and binding on too many occasions. At the end of the day for me, I can ski safer with my self adjusted binding delta than I can with the wrong net ramp.

    1. I have been advised that shim plate kits are available for most, if not all, race bindings. The race department for Marker sent me a shim kit which I will post on soon. Lou Rosenfeld, who has written 2 posts on boot board-binding ramp angle for this blog, also advised me that shim kits are available for most race bindings. When I inquired at several ski shops in Whistler, staff were not even aware that ramp angle was an issue. Further, they told me that they would not shim bindings without shim kits and technical data sheets from binding makers because of justifiable concerns for liability should a binding separate from a ski or fail because it has been modified. The key is to use the correct length of screws and install the shims correctly.

      I am currently working with several racers who have had their bindings shimmed to flat or to a small amount of positive (toe) down ramp angle. I intend to post on my analysis of why a small positive ramp angle helps load the shovel of a ski when the inside edge of the outside ski is engaged.

      I am perplexed by the fact that boot board/binding ramp angle seems to be recognized (rightly so) as a significant factor in ski racing, but not in recreational skiing where there appears to be no standards and boot board/binding ramp is typically all over the map. The industry should either justify why boot board/binding ramp is not relevant or conduct research and agree on an industry wide standard for an acceptable boot board/binding ramp angle range for all applications.

      I am going to ask Lou Rosenfeld if he will agree to write a post on methods for shimming race bindings. For now, the only option I have found is to equip my own skis with race bindings. I welcome any comments from the ski industry on what I see as a critical issue.

Comments are closed.