Took my Dynastar “Big Trouble” (5 year old, 92mm waist twin tips) in for a base grind, structure and edge angle set the other day. (Local shop having a half-price sale on tune ups.) Bases had become convex in the center 1/3 of the ski (boot/binding area) and base edge angle exceeded 1* (from too much base edge touch up – I know, my fault, but they needed it) plus just skiing them hard last couple of seasons without a base grind. After getting them home I noticed that base still wasn’t completely flat out to the edges and in fact my 1* base edge angle guide would no longer allow my stones to even reach the base edge (testing with felt tip marking pen). Returned skis and shop personnel agreed – bases not flat, still convex and they’ll fix it. Shop tech called next day to say that the sintered base material (specifically the clear vs. the black) that Dynastar uses is so dense that his Wintersteiger base grinder is unable to grind it flat. A grinding stone with embedded diamond chips verses polyethylene plastic? Obviously no contest. Didn’t argue over the phone - tech was extremely polite, apologetic and offered to return my payment. However I just know there must be a mis-communication (or operator error) somewhere and prior to picking them up I wondered if any of you folks familiar with operating the Wintersteiger (I know there are many different models) might have some clue as to what he was doing wrong. These skis (I have two pair, other has black bases) have both been ground and structured in years past with no problem. I do all the other maintenance / tuning and have never noticed any difference in base hardness between the Dynastars and my other skis. Ideas?
Sintered Base Too Dense for Wintersteiger Grind ??
Not true. My guess is that they don't know how to use their grinder. You can change the aggresiveness of a stone by dressing it accordingly. They probably have their stone dressed for final grind (med-fine structure, not deep). With this type of structure, it would take 30-40 passses per ski, to flatten a severely base high ski. I would say the tech prolly didn't do enough passes. What the tech should of done is dressed the stone with an aggressive deep pattern first (pre-grind or rough grind) - then its usually only 4-6 passes to get them flat. Then redress with a finer structure, and grind around 10 passes, until the rough grind structure is removed. Wintersteiger and Montana stone grinders have different process methods. Wintersteiger requires the base edge to be bevelled and not touch the stone (grind until you see sparks), Montana allows edge contact with the stone, and the base edge bevel is performed post grind.
And like A-man says, it could also be a structural issue - but I think its more of a grinding issue. I have ground those skis before, without any issues. What I worry about when grinding a base high ski, is that there is a good amount of risk that I may grind through the ski.
hope that helps
- 196 Posts. Joined 3/2009
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Thank you both for the response and insight.
Aman, I suppose it could be structural however nothing (structural) seems to have changed over the few years I've owned the skis. Since the tech thinks the base is just too hard/dense for his grinder I suspect like Chenzo suggested he just needs to set the stone to a more coarse linear structure for the rough grind.
And Chenzo, thanks for that input from one who's "been there done that". Tech made the comment that he made many many passes with the "highest pressure available", all to no avail. Sure sounds like a stone dressing issue. Hope he didn't ruin my skis in the process since I noticed in the Wintersteiger "Grinding Manual" that sintered bases require "lighter" pressured than extruded bases during the rough grind phase. And, re. the potential for grinding through the PTEX on convex bases - well they are about 5 years old so if it happens, it was time. Besides I really think if the PTEX is thin that it's it's the base material along the outer edges in the center third of the ski that is worn. These were skied hard, on edge and with way too much fiddling with the base edge to keep them looking decent. (Something I've stopped worrying about since learning about tuning skis from all the great info on this site.)
- 32,726 Posts. Joined 12/2007
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Depends on what you say within earshot of the tech?
Side question for folks with base grinding experience. Would it be possible to burn the bases if they tried too many times with the fine instead of coarse setting?
hahahaha - nice one!
Generally I would say no to burning - although if the base was examined under magnification there would be deformation to some extent.
But, what does happen, usually on SL's, is that the ski can become railed from overgrinding.