Base grind (full tune) questions.

[Goose]

How many base grinds can a ski endure?
And how much does each one affect the ski's integrity or perhaps better asked how much does each base grind cause the ski to lose anything from its factory designed performance intent?
The amount of skiing I do and where I ski, this is not something Id need to do much of at all. And id assume most people don't either. An edge and wax are probably all that is needed for most people most the time.
But I assume many skiers do have the need for this to be done more often and certainly many in this community of skiers. So I was curious only because I am getting this done now due to some base damages, how many base grinds and how does even just one affect (if at all) the skis?

And on another note, what about scratch groves into the bottom (base side) of the steel edges? Id assume some of them can be deeper than what a base grind would normally take off in order to make those groves disappear completely. So how much does any of those left over scratched groves affect the skis ability to carve especially in what are normally harder pack and/or icier conditions?

Id assume most people (including me) are probably no where near truly good enough to actually notice any drop in performance anyway. So for me this tuning is probably more about simply taking care of my expensive equipment. But still I wonder about its affects and just where and when does it all add up and what really matters (or not) for the average recreational skier.

 

[Sibhusky]

As @Doug Briggs said in another thread, it's not the grind itself that's the issue, it's who is doing it. A grind is not the same thing with every occurrence. Are they grinding to remove scratches (a ludicrous thing to do in most cases), to flatten the ski, to reset the base bevel, to impart structure? Those are going to produce different levels of base removal.

 

[James]

The only way to sharpen base edges for most people is to grind the base. At some point, edges become rounded enough that just sharpening from the side doesn't work. Or, you'd have to take away alot of metal on the side to get through the round part. So it makes more sense to grind it.
If skis are just not holding even after you've just filed the sides, likely this is why.
Bases can also become non flat from riding more on the edges.
Bases don't need to be pristine- no scratches, but almost everyone will grind those out because this is what people expect. I just saw a Head Rally ruined in one year from excessive base grinding with a season tune. The ptex was so thin it just fell off.

Missing sections or divots in ptex underfoot greatly affect performance on hard snow. Especially grippy manmade.

Btw, "factory tune", can be atrocious.

If one skis soft snow all the time or bonafide packed powder, most of this doesn't matter. Just smoke a doobie and tell everyone how tuning skis is stupid.

 

[Goose]

says what they do sometimes if the gouges are too deep to flatten via a grind but not deep enough to fill in, then they sometimes gouge them out so that they can then be filled and then a smooth bottom be created without unecessary over grinding

 

[Doug Briggs]

I'm of the mind that a few shallow scratches in the direction of travel that aren't near the edges can be left unfilled. Near the edges, a gouge, even shallow can cause the ski to be epecially grabby. Any gouge that exposes the edge should be fixed as it can allow the next rock to get a good hold on the edge, potentially ripping it out.

What kills me are the guys that use their skis to open their bindings, then bring in their skis for a full tune with ptex. Stop ruining your bases by taking your skis off with them and you'll get more respect from your tuner.

I wouldn't gouge a shallow defect to make it take ptex better. I'll ptex most of the gouges that I evaluate as an issue and leave some. It is amazing how much of those shallow gouges disappear with a pass or two on the 100 grit belt (which currently is less than fresh) and then a pass or two on the stone. They are still there to some degree but with the fresh structure, they are negligible. The amount of ptex removed is also negligible. Pretty much as soon as the edges spark on the belt (unless the ski is concave), I am done belting it. Get the ptex and edge at the same level then move on.

As @James says, it is a matter of what condition of the ski is in. I've had coaches come in with skis that had ridiculously convex skis with one edge worse than the other. This happens when they slip courses on the same edge all season long. To get them flat and to get access to the base edge, you have remove a lot of base material. If a ski comes in for a full tune (edge, structure, wax) and the base has plenty of structure, I will only do a light pass or tow on the stone, completely eschewing the belt. When I belt a ski, it is mostly due to:

• excessive gouges in the ptex or
• concave bases to remove some edge material

Rarely do I pull out the 80 grit belt but when I do, I lighten the pressure wheel and look carefully at the ski after every pass.

Except for race skis and performance skis where every mm of edge counts, I don't fret if there are still a few innies on the base edges. The skis will perform fine, you'll mess up the base edges again and you won't have to get a new pair of skis mid-season.

You might be surprised how many skis come in base bevels approaching 2 and 3 degrees due to wear. They are slightly rounded and typically have serious convexity (base high). AND they just want an edge and wax. It is pretty much impossible to properly tune the base edges on skis like this. The best I can usually do is shine them up with the GrindRite belt edger. They'll still get a Trimjet side edging which will provide a fairly sharp edge but not help the edge to edge transition very much. They'll still have a massive base angle. Only with a full tune that removes base material can I fix the base edges properly.

It is better to get your skis tuned regularly than to wait until they are base high and the edges rounded.

Let's just say, I'm quite conscientious about what I do to other people's skis.

 

[trailtrimmer]

Finding a good operator/tuner with a good machine is the most important thing you can do. I won't anyone with a belt touch my skis, they simply can't do what a Wintersteiger or Montana shuttle can do. The guy behind the controls is critical as he'll set how deep it cuts and will take only enough material to rid the base of modest imperfections and flatten the surface. A good tuner will get you multiple base grinds and lots of life from your skis. A bad tuner can ruin them in two or three passes.

A belt tune will never get you this, but a good machine and operator will.

 

[Doug Briggs]

I can't do thumbnail structure on my Wintersteiger, I wish I could. It is beautiful. I don't know that it is any better, performance-wise, than the structures I can do, but I like to look at them.

I use a belt as an intermediate step, never a finish. Maybe on a vintage ski to match the 'structure' it would have had in the day. Blanking a ski with the help of a belt in addition to a course stone structure can yield a finish that is perfect. You just have to make sure you belt to a point where you still have the material needed to apply the stone structure to; this ensures that the belt 'structure' is totally replaced by the stone structure.

 

[Kneale Brownson]

It is better to get your skis tuned regularly than to wait until they are base high and the edges rounded.

Or maybe do some filing on your own whenever you need new wax.

 

[Jacques]

Don't sweat the small stuff. This hand scraped structure hauls the mail!

 

[trailtrimmer]

You just have to make sure you belt to a point where you still have the material needed to apply the stone structure to; this ensures that the belt 'structure' is totally replaced by the stone structure.

And this is why I'd trust a guy like you to do a base grind on my skis. Minimal impact for maximum life.

 

[Mike Thomas]

Skis can be ground (not that 'a grind' is any kind of uniform measure) dozens and dozens of times, if each grind is a light touch-up. If you wait forever to grind your skis flat in the hope of 'saving' your skis... well, I have some bad news- it doesn't work like that. Edges, and the ptex next to the edges, wear with use on abrasive snow (all snow is abrasive to some degree), so in order to get a ski flat and the edges sharp, the non worn down material toward the middle of the ski has to be removed. Basically you can have small amounts of base removed relatively often and have a great skiing ski, or have large amounts of material removed infrequently and have skis that perform like sh!t. I do not understand the later. At all. A small portion of skiers over-do it with base grinds... but they are the outliers. The vast majority of skiers paid good money for high performance skis that are crippled by lack of maintenance. They might as well own low-end package skis.