Wilhelmson

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Is it appropriate to request an exchange if I received new skis with concave (maybe 1 mm) bases? They are not mounted with bindings.
 
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jmeb

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Is it appropriate to request an exchange if they received new skis with concave (maybe 1 mm) bases?
If it is actually 1mm, then absolutely. Bases are only 1.4mm thick on average. To get it flat, you're going to have to grind through a lot of the life of your skis.

If it less than 1/2 a mm, then sadly that may be within manufacturing tolerances. Unless you're racing, as long as your bases are close to flat, and you have bevels nicely set, you can deal with a smidge of concavity in the middle. (No one will approve of this I know.)
 

Doug Briggs

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Definitions: 1) edge high is when you can drag your fingernail across the base and it gets hung up on the edge because it protrudes beyond the p-tex. 2) concave is when there is space under the true bar from edge to edge but the base edge is flush with the p-tex.

Concavity is a lot less problematic than edge high. If you have flat bases for .5 to an inch from the edges, don't fret. Even truly concave edge to edge may or may not matter depending on whether it is outside of the contact points.

Does anyone remember Atomic Betas? They all came concave at the tip and tail. Atomic said that was 'correct' and wouldn't warranty them as defective. Nowadays I see more convex (base high) bases than concave. Especially with fatter skis and indie manufacturers.
 

James

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Is it appropriate to request an exchange if I received new skis with concave (maybe 1 mm) bases? They are not mounted with bindings.
You could try. The exchange could be as bad as the first one. Or worse.

This is less common than it used to be but frankly, par for the course. All racers just a few years ago used to get their skis ground and structured before even seeing snow.

I've had quite a few demo skis that were horrendous. Some factory tuned, others post factory. Ironically, I've had the worst demos in Switzerland, land of the tuning machines. Though this year France moved to top of the worst. I had to go pay and rent a ski from another store rather than waste two hours going back to exchange a ski that was unskiable and dangerous.
 
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Wilhelmson

Wilhelmson

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Both skis are concave as indicated with a true bar and flashlight. They would probably ski "fine" however for ease of tuning and general quality I would prefer a flat ski.
 

James

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Both skis are concave as indicated with a true bar and flashlight. They would probably ski "fine" however for ease of tuning and general quality I would prefer a flat ski.
Well talk to the shop. If you trust this shop to grind them, negotiate like a pro price grind. It's not the shops fault the ski company delivered the product in this condition. Again, it's common.

If you don't trust this shop, or your ordered it online, just take it to someone you trust. It's the cost of new skis.
 

Noodler

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Slight concavity (of less than 0.5mm) is fine as long as you're not edge high as Doug noted previously. This is more common with wider skis. What skis are we talking about?
 

ski otter 2

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In my experience, usually a concave ski will ski fine, but maybe not. The description of @Doug Briggs is pretty much the accepted common wisdom from experience on this, that an inch to even half an inch of base flatness in from a flush metal edge will usually mean the ski handles fine. But, that concavity can mask hard to ski problems/handling also. It's a risk. That much concavity is a sign that the ski may have been poorly prepped - or even poorly made, at the factory or by whoever did that.

I suggest using this concavity as a red flag for a closer look: really notice and trust what your straight edge with bright light shining under it is showing you, inch by inch along the ski, and especially in the foot and half foot around the contact points.

For example, is there an unusual rise or warp in the contact areas? Does the concavity extend unevenly towards the edge, right up to it in places? Is it worse on one side of the ski than the other? Looking down the ski, is it a symmetrical concavity or is the ski warped to one side or another, or unevenly concave left to right? Is it wavy or bumpy also, in its concavity? And are both skis the same, or concave differently? (To figure such stuff out, I'll usually take the skis into sunlight, in addition to using a straight edge with a strong light source behind it indoors.) Such stuff can really impact the way a ski handles, and how much and what sort of tuning it needs.

Note: I've found personally that many ski shops with machines like the Wintersteiger routinely leave skis concave more than one would like, as a matter of course - especially wider skis, I'd guess - sometimes, in my experience, a deeper concavity than 1 mm. In other words, I've had shops hand me skis they've worked on that are more concave than when I brought them in. I can think of 3-4 nearby shops that have done this sort of thing with my skis over the years.
I'll bet that Doug's shop, Racer's Edge, in Breck, is not one of those shops. They know what they are doing with boot-fitting, with all types of boots, and dollars to doughnuts says they are similarly good with base-flattening also, though I'd like to ask them about that.

Base flattening, especially with wider skis, can be a lot of elbow grease by hand, especially if one has an injury or is getting older. I've done it myself for some years, off and on.
 

Doug Briggs

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Is it appropriate to request an exchange if I received new skis with concave (maybe 1 mm) bases? They are not mounted with bindings.
If anything nowadays wide indie skies are base high (convex), particularly outside the contact points. High production skis tend to be concave, but not as badly as some like the Betas.

If other skis of the same model at the same store aren't concave , then I think asking for another pair or some base work, depending on your preference would be a good idea. If all the same skis of the same model are concave then it is probably unavoidable.
 

LiquidFeet

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If anything nowadays wide indie skies are base high (convex), particularly outside the contact points. High production skis tend to be concave, but not as badly as some like the Betas.

If other skis of the same model at the same store aren't concave , then I think asking for another pair or some base work, depending on your preference would be a good idea. If all the same skis of the same model are concave then it is probably unavoidable.
Every time this concavity thing comes up, I remember my Atomic Beta Carve R11s. They were really concave. I read somewhere online back then (so it must be true, right?) that the concavity was intentional. I was a new skier so my skillset was minimal and I could not tell when a ski was misbehaving or not, and I have no idea whether the source of that information saying Atomic made the bases concave on purpose was good or not.

I'd like to hear more about the Atomic Beta skis and their tendency to be concave. Was this really intentional? What bad effects did it produce? I had to use a credit card, bent, to scrape the wax off them.
 

James

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Ha, I had a pair of Atomic 9.34 188 slalom skis. 34meter! This is like '00/01. Got them the year after they came out for cheap. I took them to a good shop near where I was doing a clinic. Wanted them to flatten them. They went crazy doing it. Charged me $65. I was getting grinds then for $20, so this was sort of insane. It was way out of flat but it didn't need to be perfect..

Then I took one or maybe two runs the next day, hated the ski and sold it on ebay. It was wildly inappropriate for the guy who bought it but he was super pysched to get it.

What I remember is the beta tubes picked up the pressure wheel and the center bent down more, thus taking off more material in the center in the front of the ski
 

KingGrump

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I don't ever recalled having tuning issues with my beta lobed skis. I went through six pair from 1999 onward. 920, R11, SL9 and 3 pairs of metron M11.
Didn't do any work on those skis myself back then. Always had them tuned at Startingate. They seem to always do a good job.
 

CalG

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Those Beta Carves sure were light! The "blue ones" any way. (I suffer from CRS)

But .040" over 3-4 inches. I wouldn't even think about it.

Base HIGH or convex on the other hand would get me going on a new ski.

Imagine how "slarvy" a ski would be with double rocker and a convex base. Pontoons!

Oh, Pontoons didn't exactly catch on, did they?
 

Tom K.

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@Tom K. what would be the benefit of convexity?
Per Eric Pollard of Line Skis: With this convex contouring, we’re able to loosen the overall feel when the tip or tail is pressured. Similar to a surfboard, the convexity adds dimensionality to the ways is which you can pressure, feather, and stand on a ski. The end result is a ski that slashes better, butters with more control, improves float, and adds speed.

Not my wheelhouse, but it sounds intriguing.
 

Doug Briggs

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I'm reluctant to buy into this as anything but marketing. I don't dispute the claims that a convex tip will respond differently than a flat one, but I'll remain a skeptic until see what they are introducing as a new feature and how it differs from their current production.
 

ski otter 2

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I know from feel that it's often modestly a good thing to leave a bit of convexity near contact points, at times (maybe not with a race ski, with a recreational ski?). It seems to be a bit like the prow of a boat, very slightly, giving a stability and forgiveness to the ski's forward play/carve. I was taught years ago to leave a bit of this "prow" effect if it was there, especially towards the front. By hand, that was easy to do - both to notice and to leave it - work around it subtly.

I know in his videos, @Jacques suggests doing the same thing.
 
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ski otter 2

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At the shop I'm around most, this spring, every wider Volkl V-Werks in stock (Katanas and Mantras), and a new pair of such Mantras I brought in myself, were badly concave. On close inspection, we found they were warped, uneven, right up to the edge without being particularly "edge high," by Doug's definition. The bases thus "peaked" at the edges in waves or ripples, the whole way: enough that when a ski was worked on for base flattening, it formed what are known as "bird bath" ovals, in "pools" along the base, and in smaller metal ovals along the side edges. At least 1 mm deep concave also.

All current in stock 18/19 Volkl V-Werks- half new Mantras and half Katanas.

And, with the pair we inspected more closely, my own, the skis were both irregularly off in the same way, as if out of the same lopsided mold from the factory, or the same "off" tuning machine/technician.
 

crgildart

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They should market convexivity as "side rocker"..
 
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