Wednesday, February 2, 2011

Silvretta Pures on Karhu XCD Guides

A friend of mine came over the other night to mount a pair of backcountry skis. He had bought a pair of used Silvretta Pures and wanted to mount them on Karhu Guides. He has scoured the Tahoe area in search of a mounting jig, but none were to be found. So he came to the house of Silvretta to get er done.

One thing that I noticed was that the size medium bindings were rather larger, and would not adjust down to his 305mm boot sole. Most medium AT bindings seem to accommodate a size 8 mens, even the older 500's. But not the Pures. So before we mounted the bindings we had to cut them down. Silvretta bindings are the only bindings I know that can be made sorter by simply cutting down the rails. Though the steps involved are basic, I would not call the task simple. First you have to figure out how much to cut. I thought that the binder should be in the middle of its adjustment range after it had been cut down. Next we punched out the roll pin that held the rails in. Cut down the rails to the predetermined length. Re-drill the roll pin holes on the new ends of the rails (this was the the most difficult part, a drill press would have helped significantly). Then reassemble.

The picture at the very top shows one binding disassembled. There are roll pins located both in the front and the rear of the binding. We drove out the front pins, removed the heel unit by unscrewing the length adjustment, and slide the unit all the way forward. This left us with only the two rails and the rear connecting piece. With only two rails it was easier to hold in a vice for drilling. A hacksaw was selected for cutting down the rails. A few quick strokes and the rails were shortened. As I mentioned earlier, drilling the holes were the most difficult part. Not only do you have to make sure they are in the right location along the length, but the two holes in the right location radially. I recommend using a smaller drill and drilling both holes in one pass. Then enlarge the holes if needed. There is a chance that the first hole will already be large enough since it used as a guide for the second hole. Marking the hole location by inserting the rails into the binding is a good idea. But I would not use the front section of the binding as a drill guide. You can increase the hole size of and not allow enough grip for the roll pin. Here is another write up on shortening Pure bindings .

Once the binding was shortened, it was time to drill some holes and mount up the binding. Since the hole pattern for the Pures differ from teh 500's. I did not have a paper template that would work. The 500's were the only binding that came with a paper template, a very good one too. Instead I downloaded one from, click here for the link. The trick to using these templates is to draw an accurate center line on the ski. I will not go into the step by step details of mounting this binding, as it is covered over on Wildsnow .

What was more unique than the Silvretta Bindings, were the skis which they were going to be mounted to: Karhu Guides. Karhu ski Company is best known for its cross country skis. Specifically back country type XC skis with metal edges and scales. Their XCD series at the time of release toted the widest production fishscaled patterned metal edge ski: the Karhu Guide. At 78mm underfoot, it was a downhill ski with the ability to go cross country without skins. Why fishscales and not skins? Though skins are still required for climbing anything that is very steep, often times the terrain encountered is more rolling. This type of terrain can be frustrating with the constant attaching and removing of skins. With such a wide patterned base fairly steep hills can be conquered without having to put skins on.

The fishscale bases themselves are unique. The term fishscale is often used generically for any patterned bases that provides "one way" glide. Most fishscales are not fishscales at all but machine cut angled grooves in a flat base. Producing fishscales requires the bases to be molded with the fish scale pattern. This is more expensive, but results in better grip and better glide. Cross country skis that have scales are often called "waxless". Waxless referes to the fact that you do not need to apply kick wax to grip the snow. Kick wax is a special type of wax that not only provides grip but also glide. Though kick wax is typically superior to scales, it needs to be matched to the snow conditions and temperature. If you have the wrong type of wax on it is possible to be left with a pair of skis that either does not provide any grip or any glide. Typically "waxless" type XC skis still require wax. They need a glide wax like any other downhill type ski. This is because the base material is made of petex which is porous. If the base material is dried out they will absorb water from the snow and clump. The Karhu XCD series of skis uses an "Omnitrak" no wax base. The base material is not the standard petex, and is not porous. It is more of a plastic like material. It truly is a no wax base. In the season and a half of use they have never clump or had snow freeze to them. Though what might first appear to be a maintenance free miracle, the Omnitrak base does not glide as well as a conventional waxless base. Oh well; you win some you lose some.

If you are looking to buy a pair of Karhu XCD Guides you might find that some of what I talked about to be not longer true. The Guides are no longer the widest production metal edged skis with a patterned base. That title is now given to the Rossignol BC 125 with a 95mm waist. If you have been shopping for a pair of Guides you might find that they are in very short supply. K2 Sports, the owner Karhu Skis, has discontinued the Karhu XCD product line. They are now producing them as Madshus Annum. The Annum is the same ski but with different graphics.

Now that these babies are all mounted up let's go out and ski them...

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