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Relationship between boot flex and skier weight?

post #1 of 47
Thread Starter 

Hi, all you boot experts.

 

I have a question that's maybe very dumb but it's started me thinking. 

 

A friend of mine who is a very good skier just bought some new Rossignol boots (don't ask me what model, I don't know) that have a 130 flex.  These boots are significantly stiffer than his previous boots and I think his skiing has deteriorated since he's been on the new boots.  He seems to be LESS precise in his movements and nowhere near as "on" his skis as he was.

 

I ski a 130 flex boot and I outweigh my friend by about 40 pounds.  It seems intuitive to me that a lighter skier might not need as high a boot flex to get the same degree of performance as a heavier skier, but I've never seen much discussion of this question.

 

Weight has a huge impact on ski performance.  Does it have the same impact on boot response?

post #2 of 47

I think it does.  I think that boots that are too stiff lock up the ankle joint.  Without the ability to flex at the ankle the skier generally overflexes at the knees and waist and winds up skiing from the back seat.  My wife bought a Lange 150 after I advised her not to, because it was "a good deal".  She has finally dumped that boot and is skiing much better in a boot that she can flex.

 

Additionally the flex numbers mean very little as there is no standardization in the industry.  My 130 Nordica doesn't flex the same as your boot or your friends Rossi.

post #3 of 47

The flexibility of the boot is far from being the most significant factor in boot performance.  The overall fit (snugness) and various stance angles are significantly more important IMHO.  For example,  I have a difficult to fit foot (long, narrow),  and I am MOST concerned first with the last width,   then the fwd lean.  From there,  I can tweak a boot to work.  If the boot is too wide,  I guarantee my skiing will completely fall apart.

 

My guess is that the new boot is not fitting as snugly,  which is causing your friend problems.  The flex isn't what's holding him back.

 

AM.

post #4 of 47

I'm 135lb and ski the Technica Agent in a 130 flex. works for me very well. like you said, hard to compare brands. And your friend may have any number of issues with the Rossignol boot, hard to isolate what characteristics of the boot are not working for him. I have heard that many 150 flex boots are just too stiff for freeride skiing. 

post #5 of 47

I'm no expert Bob, but I have struggled for a while with boot issues. At first I thought the same thing, I had come from really soft boots and went to a 110 plug-lite and never felt right in those boots. I took steps backward right away.

 

Turns out, from trying a couple other moderate flex boots my problems were the same and came from stance and size issues. I really wish forward lean and ramp angle data was more consistent and accessible because that would have saved me a lot of headache. I needed less ramp angle to get balanced without being overflexed to begin with. My quads were burning just standing in the lift line after a few runs because I couldn't stay forward enough.

 

I also think that a person with longer tib/fib can get more leverage on the boot when flexing, so a lightweight guy with long legs might be able to do more than you'd think.

post #6 of 47

 

Quote:
The flexibility of the boot is far from being the most significant factor in boot performance.  The overall fit (snugness) and various stance angles are significantly more important IMHO.

+1

 

If the boot is the correct fit and geometry for that skier, then the flex might be the problem.  Flex can usually be softened.  I know some expert mid-weight skiers in 150 flex plug boots, but they're the exception.  Part of the flex equation is not only the skier's weight but the total energy the skier puts into their boots & skis.  If he is a more energetic (stronger faster) skier than you, that might be the right flex for him.  If he is both lighter and not more energetic, then he might do better with the flex reduced always assuming that boot has the correct geometry for him.

post #7 of 47
Thread Starter 

It seems as if most of the answers so far are kind of dancing around the basic question...

 

Let's say for the sake of argument that two skiers of equal height and equal bone length have exactly the same brand/model of boot that is fit perfectly by an expert bootfitter.  Our two skiers are equally good skiers who ski the same terrain and conditions with essentially the same technique.  The only difference between the two skiers is that one weighs 140# and the other weighs 190#.

 

In that situation, wouldn't the heavier skier be able to flex the boot much more deeply than the lighter skier?  How could he not?

post #8 of 47

According to the boot fitters I've worked with, I have limited dorsiflexion i.e. there isn't much flexibility in my ankles. They use heel lifts to compensate, and put me in a stiffer boot than my weight or the type of skiing I do would normally indicate.

post #9 of 47

First, I'd like to hear what boot he was originally in and what he's skiing now - because I also believe that this is more of a stance alignment thing.

 

But you would like to delve more into the weight issue.  It's my opinion (and that of another well known ski instructor, ahem) that stiffness of the boot has much less relevance as long as your fore/aft alignment is dialed in so that you do not need to flex the boot to be properly aligned.  This means that the inter-relationship between the binding delta, boot ramp, and boot forward lean must all equal a balanced stance.  Did your buddy happen to change anything else in his gear setup other than the boots this season?

 

Personally, I've gone to the stiffest setup I've ever skied this season and I feel like my skiing is getting better than ever.  I'm also 30 lbs. lighter than last season, but I have also spent lots of extra time getting my fore/aft alignment dialed in with my new setup.  Last season I believe I had too much forward lean and ramp.

post #10 of 47

I don't think I flex the boot much, or that that is my intention. for me, press forward to weight the ski fore body, press back to weight the tails. the boot just transfers the pressure into the ski with very little flex to absorb or dampen the energy.

post #11 of 47

A very stiff boot results in a hair trigger on/off feel that is great for racing, but which I do not like for free skiing.  If your friend's old boots had a progressive flex that allowed him to modulate the pressure he was putting on his tips, it would also give him better feedback on the feel of the ski and the snow, and he probably would not like the instant response of a stiff boot. That is why Kryptons, Flexons and the like are still very popular.  Progressive flex equals better feel.  I had some stiff boots that worked great, but I felt like I had novacaine in my feet. They were not too tight, but they gave me no feel of what was going on, and consequently my skiing became mechanical and lost its joy.

post #12 of 47

My thought is Noodler is correct. If your alignment is off, the flex of the boot becomes a lot more important because you'll constantly be pressuring the boot in some way to try to reach a natural balanced position, be it fore or aft.

 

The answer to your basic question is probably yes, a heavier person should be able to flex the boot more easily.

post #13 of 47

with a soft boot I keep fully compressing it when hitting crud and abrubt terrain changes, and the flex is so far as to be painful in the ankle and shin. I also don't like the feeeling of the tip being able to come up against my pressure.

post #14 of 47

i am 5'10" and 122lbs. and i ride with Lange World Cup 130's. i know this is a stiff boot and i don't weigh much. but the stiffness allows me to precisely flex skis and keep them tracking the direction i aim them, especially in heavy chowder and crud. and in the bumps it keeps the tips down the fall line. but thats is just my experience and it works very well for me.


Edited by Gregoryv022 - 12/15/10 at 10:29pm
post #15 of 47

Wow, that's funny you started this topic.  I was just about to start it myself.  

 

I have the same question and through some testing, think I know the answer.  

 

I'm a 5'7" (shorter legs/longer torso) 145lb male skier.  Probably level 7.5-8ish.  Three years on skis.  30 years old. Athletic.  

 

I just purchased some Dalbello Krypton Pro ID boots. I had done a ton of research and decided on this boot as I wanted something that can take me through the next 4 years and be super high performance for all mountain/off piste skiing.  I really dig and believe in the technology behind the 3-piece design.   In saying this, I knew a boot at 100 flex (setup at easiest flex) would be a challenge for me.  They have the Gold ID liners which I read (on this site) add ~15% more stiffness.  

 

At room temps I can get the boots to flex OK, but not as soft as I'd like them though--and I'm not even in cold weather.  Soon as I hit the cold weather this season I'm having a very hard time even flexing the boot forward.  This is even true when standing still on the skis and trying my best to slam my shin into the boot.  By doing that test, I know that it's not my skiing 'ability' that's lacking the ability to flex the boot.  I simply can't gain enough leverage with my sawed off short legs and 145lb weight.  I'm more the size of a woman and you would never think to put a woman in that boot. 

 

HOWEVER, in saying all of this, part of the reason I went three piece was because of the replaceable tongues.  I have recently drilled ~20 very small holes in my medium flex tongues.  I'm working to soften the tongue and get me something more like a 75-80 flex boot.  But with the lateral rigidity and other bells and whistles of a Krypton Pro.  I'll be posting up some photos and results once I have more info.  If I screw up the tongues, I can always order a second replacement set. 

 

So long story short, I do think height and weight play a roll in the flex a skier should have in their boot.  Not just skiing ability.  If you don't have the weight/leverage to properly flex the boot indoors on solid ground, you're sure as hell not going to do it on a 40 degree slope in 20 degree temps... Doesn't matter how good your technique is.  Meaning you'll be in the backseat.  

 

 

post #16 of 47

I used to and think I still would prefer the precision control and instant response of my old Uber-stiff boots when going super fast on my old stiff skis, not that I get to do that these days (as in eye-watering if you don't tape up the ventilation holes on your goggles) speeds. 

 

I prefer the kinder gentler suspension of soft boots when just doing normal skiing. 

post #17 of 47

As usual, we're making a simple question complicated. Bob's right; a heavier skier will be able to flex a boot of the same stiffness more than a lighter skier, all other things held constant. Just basic physics. And also agree with Tetonpowderjunkie that an overly stiff boot will lock up the ankle joint, create bad biomechanics. 

 

I also think, though, that the question presupposes that both skiers like to pressure their tips a lot. If you have a more neutral stance, isn't lateral stiffness more relevant than the forward flex? (The two are at best modestly correlated.)

 

Finally, I'll see Bob and up his ante: I think many skiers' ability also deteriorates when they purchase stiffer skis. Which describes most modern fat carvers, for example, and many rockers. Same idea as boots; a ski that's too stiff for the forces we habitually generate will discourage us from trying to vary turn shape. We'll ride the sidecut, or ski faster than we want just to bend them a bit, or in the case of rockers, go back to the future and discover sliding our tails...you get hints of this every once in a while when someone notes a pro who skis a comparatively soft ski, and someone else says, basically, "Oh, well sure, he can keep a soft ski under control; he's a pro; I'm not that good"...snowfight.gif


Edited by beyond - 12/16/10 at 10:48pm
post #18 of 47
Quote:
Originally Posted by Benflow View Post

At room temps I can get the boots to flex OK, but not as soft as I'd like them though--and I'm not even in cold weather.  Soon as I hit the cold weather this season I'm having a very hard time even flexing the boot forward.  This is even true when standing still on the skis and trying my best to slam my shin into the boot.  By doing that test, I know that it's not my skiing 'ability' that's lacking the ability to flex the boot.  I simply can't gain enough leverage with my sawed off short legs and 145lb weight.

 

In all honesty, you should be able to flex a 100-110 boot easily outside, regardless of your leg length. Many women lighter than you ski 100 flex boots; 75-80 is typically for beginners. I suspect from your "slam" comment that you're trying to lever the fronts of the boots when you ski instead of sinking down into them, letting your weight do the work. Think about some lessons before you do anything else to your boots. Also, are you a tip pressure or a neutral skier? The whole point of the Dalbello is to create a laterally stiff boot that is comparatively easy and constant flexing to the front. That's why bump and soft snow folks like them so much, and why they can feel like you're falling forward when you first start using them. If you're a tip pressure guy, they're the wrong boot. Finally, have you tried changing the little tabs in the back to reduce the flex? Boring out the tongue seems kinda extreme. 
 


Edited by beyond - 12/16/10 at 10:50pm
post #19 of 47
Quote:
Originally Posted by beyond View Post

As usual, we're making a simple question complicated. Bob's right; a heavier skier will be able to flex a boot of the same stiffness more than a lighter skier, all other things held constant. Just basic physics. And also agree with Tetonpowderjunkie that an overly stiff boot will lock up the ankle joint, create bad biomechanics. 

 



Maybe, maybe not.....  you're assuming that the ankle is the pivot and the person is leaning forward with legs locked.  In that scenario, yes larger mass = more pressure at the shin and easier to flex a stiff boot.

 

However that is not how we ski!  We do not flex the boot by leaning forward.

 

With shoulders over knee over toes, we flex the boot by lowering our COM.

post #20 of 47

A "hundred years ago" I was riding the lift with two instructors and the one guy's comment on boot flex was that if you can't flex the boot you can't bend the ski. This was pre shaped skis so maybe if there is merit to this its discounted a bit with the advancement in skis but it made sense to me then and I think would still apply today.

post #21 of 47

@Beyond If I relax my upperbody and 'sink' into the front of the boots outside in 20 degree temps, the upper cuff does not move forward at all (some flex in the top where the liner is outside the shell, but that's not ankle flexion movement).   I've never been 'evaluate' on a tip pressure vs. neutral skier, but I would assume neutral based on how I ski.   I have the boots setup with no tabs and the soft tongue so they're as soft out of the box as they come 100 + 15% (estimate for the Gold ID liner that is not used in their initial flex measurements of 100-130 for the boot).  

 

*As far as 75-80 being for beginners??? Rental boots I've been told are in the 60's.  My last pair of high intermediate/advanced Dalbellos were 85.   Also, the top end (expert) women's Krypton boot is 75-105.  If weight and leg size had nothing to do with boot flex then why wouldn't the women's top end Krptons be 100-130?  

 

I agree that my comment of getting my boots down to 75-80 might be a bit of an overreaction given my size (145lb, 5'7") and skill level, but I certainly think that the boot should flex when I relax and 'sink' into the boot (and applying pressure to the shins). At this point they don't.  My 'slam' comment mean that even when physically trying to 'muscle' the boots (not proper technique by any means) I can still barely move them in cold temps.  

 

 

post #22 of 47
It's odd when bob Posts this question he vets to s of responses. Where I posted it months ago with only a peep. I have 2 identicle atomic cs boots one in 100 flex and one in 140. I am6' and 180. I find the 140s far superior but I am not the most graceful skiier. More balls out and hard charger with fast changes in com which is proly why I like the stiffer boots while I may overpower the prdvios boots.
post #23 of 47
This is a good question. I'm 5'6", 140 lbs. For various reasons I ended up skiing on Head RD96 boots (25 mondo, pretty stiff) all last year. For running GS gates, I actually wanted them to be stiffer. I felt that energy I wanted to go into the skis was flexing the boots instead. For SL I thought the boots were about perfect. In moguls, the boots were too stiff, requiring a precision in balance that was difficult to maintain. It was a great technique builder, but not super fun.

I did some skiing with a 20 lb backpack on. It didn't change my perception of how the boots flexed, or how I skied, at all.

The stiff boots don't give me much of a sweet spot. I either have pressure on my shins, or I'm in the back seat. I think a taller, heavier person would be able to find a neutral stance, which would make them a lot more forgiving in the moguls.
post #24 of 47

I don't think what flex you should be in has too much to do with weight, probably more to do with technique, alignment, and preference. There are a lot of very light people in very stiff boots that ski at a high level.

 

Just as an extreme example, Harald Harb has said he weighs around 148 lbs and he skis in a Raptor 150. His associate Diana has said she weighs 128 lbs and prefers the 150 flex Raptor also, but another one of their coaches is heavier and prefers a softer boot.

post #25 of 47

To OP - Bob Peters...

I am not a bootfitter, or anything just regular guy... And to answer your question yes... There is a big relation between skier's weight and boots flex..

Just one example: Kind of quote of SKI mag  from the gear test issue.....

 

Explanation of boot flex:

- 140-150 stiff as brick for elite WC male racers...

- 130 still very stiff/ L. Vonn stiff/...For aggressive advanced male experts and WC elite female racers...

- 110/don't remember/, etc..

 

So the way they/SKI mag/ are suggesting there is relation between skier's weight and boot flex. The only difference between L. Vonn and most of the WC male racers is weight, nothing else.. L. Vonn is 165lbs. or so... Most of the guys are way over that...

post #26 of 47


 

Quote:
Originally Posted by andy4g63 View Post


 

So the way they/SKI mag/ are suggesting there is relation between skier's weight and boot flex. The only difference between L. Vonn and most of the WC male racers is weight, nothing else.. L. Vonn is 165lbs. or so... Most of the guys are way over that...


The males are quite a bit stronger, which is why they weigh more. She is 5'10''.

Didier Cuche is like 5'9'' and 200 pounds.

 

It's basic human physiology.

post #27 of 47

^^^^^^^^^ Exactly, that is my point... They/men/ are stronger mostly , cause they weight more.

post #28 of 47


 

Quote:
Originally Posted by andy4g63 View Post
 The only difference... is weight, nothing else.


 

Quote:
Originally Posted by andy4g63 View Post

^^^^^^^^^ Exactly, that is my point... They/men/ are stronger mostly , cause they weight more.


Other way around, they weigh more because they are stronger (with a lower body fat %).

post #29 of 47

Weight > Strength / Strength > Weight haha chicken and the egg! 

 

....

 

I don't know how it can be denied that if you put two level 8 skiers in a 100 flex boot and one is 5'7" 145 and one is 6'1" 200 the bigger guy will have a way easier time flexing the boot. And if the flex is 'right' (per the intended design of the boot) for the big guy, it will be far too stiff for the guy that's 7" shorter and weighs ~50lbs less.

 

 

 

post #30 of 47

No, not at all.

 

And "skier level" doesn't take into account strength and style.
 

Quote:
Originally Posted by Benflow View Post

Weight > Strength / Strength > Weight haha chicken and the egg! 

 

....

 

 

 

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