Longevity of a ski

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Longevity of a ski

Postby alex_aku » Sat Oct 08, 2016 2:02 am

Hi to everyone,

maybe a trivial question (but not to me at the moment): How to recognize when the ski is up for replacement? .. when it lost too much of stiffness / rebound force due to normal usage?
I own a pair of Supershape KERS, the coming season would be the fifth for them, the skis have about 50-60 day "on them", usage 95% on groomers, rarely really high speed, till now no real bumps.
I am considering a replacement - a "default" would be SS Speed, maybe Head World Cup Rebels i.SL (many good opinions on the forum about iSL, yet I still have a concern they may be too stiff). Am looking at 170cm as default, but maybe 177?
About me: 6,2 toll (189cm), 210 lbsn (95kg), in the PMTS world since 2 years, beginner perhaps moving into intermediate (have all the books and doing every skiing day some drills at least half a day :-).

Thanks
Alex
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Re: Longevity of a ski

Postby jbotti » Sat Oct 08, 2016 12:24 pm

The best way to see how much your skis have lost from usage is to jump on a new pair. Skis start to lose some camber, some of their torsional rigidity and and the combination of both will decrease edge hold as well as rebound over time. I also find that the more times you do a base grind the faster the ski deteriorates. I have no science to back that up but is definitely my experience. I find that its is right around the 60 day mark that I start to notice some decline in performance. And this is much more noticeable past 80 days and into the 100s. Skis that are also base high (in need of a base grind) are slower for the edge to engage and they just don't perform as well. If you have never had your bases ground you might want to consider this as it will increase performance (certainly the first two times you do it). I would demo a new ski (like the SS Speed) and if you notice way more pop, way better edge hold etc you will have your answer. If you having two pairs of skis is an option you can buy the SS Speed and use it when conditions are perfect and use your old skis for days when you might hit some small pebbles etc. As well a ski that has lost a little pop is usually a little easier to ski off piste so you could use your old skis for that as well.

Now Geoffda skied a pair of TT 80s for 500 days! Some people notice it less or don't care. HH and Diana ski theirs for over 100 days each year but I rarely see them using them for a full season the following year and they usually use them when the conditions aren't great and they might damage their new skis.
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Re: Longevity of a ski

Postby theorist » Sat Oct 08, 2016 2:12 pm

One of the engineers that co-developed the Elan SCX* claims, based on some basic measurements he's done, that nearly all the loss of longitudinal stiffness due to use comes simply from loss of edge material due to sharpening (yes, it's a surprising claim, and I'd want to see more measurements before I believe it myself). He claims the same about torsional stiffness, but IIRC he's merely making an inference from his longitudinal measurements, and didn't measure torsional stiffness directly.

*JF, not spelling out his name as a courtesy b/c of the search engines, but you can find him in the Wikipedia entry for Elan.
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Re: Longevity of a ski

Postby jbotti » Sun Oct 09, 2016 8:41 am

Skis absolutely lose camber over time and this is measurable and the camber loss affect edge hold and rebound. Now perhaps his claim is that this loss of camber is solely or largely due the loss of edge metal from filing. I guess that could be the case. Interesting that in Montana in good winter conditions we really don't need sharp edges so I can often go fairly long periods of time without touching mine. Not sure the camber in my skis lasts any longer but maybe it does.

It does make sense that the more material you take off the ski the more you add to its instability.

At the end of the day skis are made to be skied, sharpened and ground. The more you do off all (the more you ski the more you need to sharpen and ultimately grind) the faster they wear out. Which means you get to have that wonderful joy of buying and skiing on new skis!!
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Re: Longevity of a ski

Postby alex_aku » Sun Oct 09, 2016 10:40 am

Thank you guys for your replies!
I guess if I take the 100 days of HH and Diana as a benchmark than I would have to postpone the pleasure of buying new skies :-)
I showed my skies also to a friend who used to do some racing (in Germany/Austria) and now does kids coaching - his recommendation was to do just a proper base grind and otherwise they are fine.
Thanks again!
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Re: Longevity of a ski

Postby theorist » Sun Oct 09, 2016 11:09 am

jbotti wrote:Now perhaps his claim is that this loss of camber is solely or largely due the loss of edge metal from filing.


He didn't mention camber specifically, but yes, that is his claim about loss longitudinal stiffness, that it's largely due to loss of edge metal from filing, rather than repeated deformation cycles—a claim I found both interesting and surprising.


....I should also add, for the OP, that skis do age simply due to storage, and that thermal cycling can have an impact on glues and foams. If you wear out your skis due to use after 3 seasons this probably isn't an issue, but if it takes you 10 years to reach 100 days/ski it could be. Particularly in the latter case, ideally you'd want to store them in a cool, dry, temperature-controlled place, and out of direct sun (not near a window).
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Re: Longevity of a ski

Postby geoffda » Tue Oct 11, 2016 6:14 pm

jbotti wrote:Now Geoffda skied a pair of TT 80s for 500 days!.

Not that many! It is possible that I spent 500 days between the two pairs I owned (one was the TT-800). I generally get about two seasons out of a daily driver type of ski. 200 days per pair is probably a reasonable estimate--keeping in mind that many of my days are 2-3 hours. But none of that really matters. There is no formula for ski longevity because there are too many variables. Experience is what tells you when a ski is done.

Like others have said, you can feel it when a ski is losing its mojo and needs to be replaced. Usually the first first sign is a loss of longitudinal stiffness which is accompanied by a noticeable loss of pop or rebound energy at release. The next thing to go will be torsional stiffness. When that starts to happen, it will be more difficult to get the ski to hold on hard snow. At that point, the ski is basically done, but depending on your skill level, you may choose to keep skiing it until it will not hold at all. As my friends can attest, that is usually what I do.
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Re: Longevity of a ski

Postby CO_Steve » Tue Oct 11, 2016 6:41 pm

I took a run on the first pair of Geoff's TT-80s near the end of their life. I'd say they were well past due.
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Re: Longevity of a ski

Postby B.Mulligan » Wed Oct 12, 2016 5:03 am

This is fun topic. It's not so much that the lose camber but they start literally coming unglued. Layers and caps loosen over time and usage-that's where that mushy feeling comes from. My experience better brands and skis with metal hold up longer and indie brands without metal lose their snap the quickest. I have put race skis through two kids and then inherited them myself with good success...though, I think that's because I need a pre-softened race ski.
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Re: Longevity of a ski

Postby Icanski » Tue Nov 01, 2016 10:06 pm

It's interesting that many skis seem to go about the same time, given being skied a similar amount. Inspite of being made of different cutting edge materials.
Head's 'liquid metal", the graphene, carbon, all these materials which are credited with being stronger than ever, and able to do amazing things, but still only for about the same amount of time.
I think 100 days of Colorado skiing, vs. 100 days of Ontario or Eastern skiing would certainly affect skis in different ways. I've been skiing my SS since 2006...time to go demo some new ones and see if I can get a pro deal. ;-)
Boots are ready for replacement, too, had new liners and all, but new boots means a trip to the skunk works for fitting, and with our dollar in the tank.....I need a lotto win.
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