When your skis performance deteriorates, it usually means one of two things has happened. You may find that your skis just need a simple side-edge sharpening. Or, potentially, the skis base material and base-edge need to be flattened, reset and restructured.
When you start your season, you may find that your skis perform perfectly… The skis roll-up to edge quickly, feel powerful and energetic. But, over time and use, the skis are subjected to powerful forces from making turns, the skis bend, flex and breakdown. Slowly, the base-bevel on a pair of skis increases, just from normal everyday use. Over time, this slow erosion of performance is hard to detect… Here are some signs that you need a stone-grind.
- Mid-season boot canting issues- Base bevel has increased.
- Burnt or marbled base material next to the skis edge underfoot.
- Skis will not hold in icy conditions, even if the edges are razor sharp.
- You are having difficulty getting wax to spread evenly across the base material of the ski.
The skis base-bevel is difficult to see with the naked eye and requires the use of a true bar to read the slight bevel. If the skis are found to have excessive base-bevel, they will need to be stone-ground until the base material and base-edge material are completely flat.
Once the overall base and base-edge flatness is achieved, then the technician can set the proper (.5 or.75 degree) base-bevel and the skis will perform at the maximum potential.
So, how do you get your skis base material and base-bevel trued and reset? You will have to take your skis to a reputable ski tuning establishment that has a stone-grinding machine for skis.
A stone-grinder is a machine that flattens the base material of a ski. There are manual and robotic versions, but they all do the same thing, flatten and structure the base of a ski.
When the base of a ski becomes warped, concave, convex or edge high, the stone-grinder resets the edge and flattens the base material. This flattening is performed by using a composite grinding wheel to true and flatten the base of the ski. The skis base surface is then sent over the stone, with varying speeds and passes, flattening the base and base-edge material.
Once the base and base-edge material are flattened, then the appropriate base structure can be applied for varying snow conditions a racer will encounter. The composite wheel is trued and dressed by a diamond bit that sets a pattern by traveling across the face of the stone.
The pattern left by the diamond bit is either a straight linear or broken cross pattern. By changing the speed of the composite grinding wheel and the diamond bit, the technician can create limitless patterns that can be used for flattening the base material or selecting a structure pattern that is specific for different snow conditions and temperatures.
*Examples of base structures/snow crystals
Just as with selecting tires for car racing, a driver may use slicks on a dry track or a deep tread pattern for wet conditions… Selecting a specific pattern for a skis base material can maximize glide. Usually, wet/warm conditions require a structure with depth and width that helps move water underfoot, whereas cold dry conditions require a smooth structure that helps hold a thin layer of water under the ski.
Should your skis be stone-ground, even if they are brand new? The answer is maybe!
When skis are new, they usually need to be flattened, the base bevel on new race skis is generally 1 degree or more. Most racers will want their base-bevel to set at .5-.75. As mentioned before, even if the skis have been stone-ground when they were new, general use throughout the season will twist, and break down the core structure of the skis. These forces will naturally cause the skis base material to fall out of true, along with increasing its base bevel, leaving the skis feeling sluggish and slow to edge.
When looking for a stone-grinding location, there are a few things you should consider.
- Does the store have a staff that is familiar with ski racing?
- Are the technicians at the store able to explain bevels and structures to you with confidence?
- Do your coaches recommend a certain store in your area?
- Finally, see if you can get a tour of the stores tuning facility, is it clean and organized?
After stone-grinding and setting the base bevel it is important to sharpen and touch up the side-edge material.
A proper sharpen and touchup of the side-edge bevel will leave your skis feeling powerful and predictable. When dropping your skis off for a stone-grind and base-bevel, make sure that you specify that you need your edges finished off if you are not planning to do it yourself.
Many of the shops across the country have very precise stone-grinding machines capable of elite level side-edge finishing. These machines can leave your skis with a super sharp, high polished edge appropriate for ski racing.
For example, Grip-Tech edge finishing from Montana offers precise edge angles and a quality edge finish. It also grinds the functional edge, from the tip to the tail of the ski. The Grip-Tech edge sharpness lasts longer, and in most cases, the machine removes less edge material overall than using a traditional file.
After most machine sharpening, you will find that your skis might only need a simple stone touch-up after a day of training on the slopes to return the edges to race sharpness.