Grip physics?

Hi All,

I have been thinking about grip, and kick and how my technique and size
play into my performance in low-grip conditions.

I am heavy (100kg, 225lbs) and do not have great technique (yet!). My
skis are on the stiff, cold side. In good cold conditions I have great
grip, the skis feel nailed down and I can get all my power to the
ground, even on steep inclines.

In low-grip icy conditions it is a different story. I know softer skis
would help, and most of all better technique, but I wonder what my
weight means on steep slippery inclines. I can't get any power down. It
seems like I have it worse than others I've seen. Is my weight a
factor, or is it just the other variables?

Traction is a function of how much down-force is available (from weight
and rythmn), but what are the limiting factors? To get my weight up a
steep incline as fast as my fitness allows I need to get more power to
the ground in slippery conditions. Does my need for power due to weight
go up faster than my weight's ability generate friction as the incline
get steeper?

Thanks!

Joseph

I can't answer this on-topic, but I wonder, with which technique are you
getting into trouble?

I know that in MTB, with a heavish and super-tall body, I DO can get the
traction I need, from the same tires as racer types. My weight indeed seems
to add the required friction. I also have sufficient grip in corner, even
though more weight is further away from the ground.
The way I put my power down on tires makes all the difference on steep
climbs, I need to be smooth, non-agressive, or I'll slip, same with short
people. I've learned his over the years, and can now use it in my advantage
even in the most slippery conditions.
I wonder how ski length affects all this. Do longer ones provide more
directional (classic) and sideways (skating) grip on snow? It does work that
way with tires, wider ones, or those with a larger radius, grip better and
more predictably.

schreef in bericht
oups.com...
Hi All,

I have been thinking about grip, and kick and how my technique and size
play into my performance in low-grip conditions.

I am heavy (100kg, 225lbs) and do not have great technique (yet!). My
skis are on the stiff, cold side. In good cold conditions I have great
grip, the skis feel nailed down and I can get all my power to the
ground, even on steep inclines.

In low-grip icy conditions it is a different story. I know softer skis
would help, and most of all better technique, but I wonder what my
weight means on steep slippery inclines. I can't get any power down. It
seems like I have it worse than others I've seen. Is my weight a
factor, or is it just the other variables?

Traction is a function of how much down-force is available (from weight
and rythmn), but what are the limiting factors? To get my weight up a
steep incline as fast as my fitness allows I need to get more power to
the ground in slippery conditions. Does my need for power due to weight
go up faster than my weight's ability generate friction as the incline
get steeper?

Thanks!

Joseph

Jan Gerrit Klok wrote:
I can't answer this on-topic, but I wonder, with which technique are you
getting into trouble?

Diagonal stride in icy-tracks. I feel like I can only push with a
fraction of my available energy. This is of course the same for
everyone, but I suspect weight makes this a problem on climbs before it
is a problem for lighter people.


I know that in MTB, with a heavish and super-tall body, I DO can get the
traction I need, from the same tires as racer types. My weight indeed seems
to add the required friction. I also have sufficient grip in corner, even
though more weight is further away from the ground.
The way I put my power down on tires makes all the difference on steep
climbs, I need to be smooth, non-agressive, or I'll slip, same with short
people. I've learned his over the years, and can now use it in my advantage
even in the most slippery conditions.

On steep climbs, it was usually wheelies that were my problem, not
grip. Now I have a 2-wheel drive bike so I can stand up on really steep
climbs and move the center of gravity forward to even the load. So no
wheelies, and no slipping.

I wonder how ski length affects all this. Do longer ones provide more
directional (classic) and sideways (skating) grip on snow? It does work that
way with tires, wider ones, or those with a larger radius, grip better and
more predictably.

The grip-zone on my classic skis isn't that much bigger area-wise than
my wife's skis, though I weigh at least 40kg more than she does.

As for tires on cars, whenever I see a car that is having problems
getting up a icy hill, it is usually a larger car, a truck, or heavily
loaded small car. I used to have a BMW 318 and a 520. Both with the
same size winter tires. The 520 weighed about 400kg more. It didn't
slip as much when I gassed in in the turns despite more power, but it
also had more difficulty starting on icy surfaces and getting up hills.
Ice is funny stuff.

Joseph

schreef in bericht
oups.com...
Hi All,

I have been thinking about grip, and kick and how my technique and size
play into my performance in low-grip conditions.

I am heavy (100kg, 225lbs) and do not have great technique (yet!). My
skis are on the stiff, cold side. In good cold conditions I have great
grip, the skis feel nailed down and I can get all my power to the
ground, even on steep inclines.

In low-grip icy conditions it is a different story. I know softer skis
would help, and most of all better technique, but I wonder what my
weight means on steep slippery inclines. I can't get any power down. It
seems like I have it worse than others I've seen. Is my weight a
factor, or is it just the other variables?

Traction is a function of how much down-force is available (from weight
and rythmn), but what are the limiting factors? To get my weight up a
steep incline as fast as my fitness allows I need to get more power to
the ground in slippery conditions. Does my need for power due to weight
go up faster than my weight's ability generate friction as the incline
get steeper?

Thanks!

Joseph

On steep climbs, it was usually wheelies that were my problem, not
grip. Now I have a 2-wheel drive bike so I can stand up on really steep
climbs and move the center of gravity forward to even the load. So no
wheelies, and no slipping.
For some reason bike manufacturers give everyone from 1m30 to 2m30 the exact
same chainstay (horizontal rear fork) length. So, taller riders tip back
over more easily. Bike manufacturers care more about cheap production and
large easy sales than designing stuff that actually works well for the rider
that's buying it. I suppose if a ski maker put the same length grip area on
both kids' and your ski's, a very similar situation. I am a passionate
believer that everything in sports goods should be proportionate to the
athlete's body.
I won't get too much into bikes here, I have another place for those rants
of mine (www.mtbr.com , I post as Cloxxki).

I wonder how that works out with ski width. Does that stay the same for 30kg
kids and 100kg men? would we biggies suffer if ski's were made wide, and if
so, why?
To my newbie popular-science-fan eye, not affected by 100 years of ski
evolution, it seems like Joseph would like ski's to match his leg length,
with a width to match his weight. If someone knows links to any studies on
that subject, I'd appreaciate those a lot.

Jan Gerrit Klok wrote:
On steep climbs, it was usually wheelies that were my problem, not
grip. Now I have a 2-wheel drive bike so I can stand up on really steep
climbs and move the center of gravity forward to even the load. So no
wheelies, and no slipping.
For some reason bike manufacturers give everyone from 1m30 to 2m30 the exact
same chainstay (horizontal rear fork) length. So, taller riders tip back
over more easily. Bike manufacturers care more about cheap production and
large easy sales than designing stuff that actually works well for the rider
that's buying it. I suppose if a ski maker put the same length grip area on
both kids' and your ski's, a very similar situation. I am a passionate
believer that everything in sports goods should be proportionate to the
athlete's body.
I won't get too much into bikes here, I have another place for those rants
of mine (www.mtbr.com , I post as Cloxxki).

I'm a big fan of proportionality too. That's why I use 195mm cranks on
my bike!

I wonder how that works out with ski width. Does that stay the same for 30kg
kids and 100kg men? would we biggies suffer if ski's were made wide, and if
so, why?

I think the issue is surface area to skier weight, and certain ratios
for certain usage. Ie racing skis go on packed trails so they don't
need as much float, while back-country need lots of float. And then the
area is limited by practical issues like track width, and controllable
length, and predictable flex.

I use 210cm classic, and 195cm skate. I would have no problems using
even longer classic, but the 195 skate gets crowded on narrow climbs.
It may be that way for everyone, I don't know, but with a 96cm inseam,
and 195cm skis going 90deg to each other, that gets pretty wide.

To my newbie popular-science-fan eye, not affected by 100 years of ski
evolution, it seems like Joseph would like ski's to match his leg length,
with a width to match his weight. If someone knows links to any studies on
that subject, I'd appreaciate those a lot.

I suppose narrow glides better, otherwise why would racing skis be
narrow? Give me length!

Joseph

I'm a big fan of proportionality too. That's why I use 195mm cranks on
my bike!
I envy you, longest I have is 185mm, and I've got a 99.5cm inseam!

I suppose narrow glides better, otherwise why would racing skis be
narrow? Give me length!
Too narrow and it would appoximate speedskating ski's (knifes), that would
go no-where. There must be an optimum somewhere, but I can't believe it's
40-45mm for every skiier of any height or weight.

Lets be honest Joseph.
No 1 Your technique is probably wrong.
being as heavy as you are a 210 ski will be flat on the snow all the
way.
It is almost impossible to find a classic ski today that will give a
person of your weight a good grip to glide ratio.
So you should have wonderful grip at any rate.
at any snow conditions.
In climbing a hill on xc skis people tend to lean forward too much.
This will reduce your grip zone
and your grip in general.
Try and put your weight of your upper body on the toe of your boots ins
climbing. This will apply all your 220lbs on your real grip zone.
Also chose your wax well.
rw

rw wrote:
Lets be honest Joseph.
No 1 Your technique is probably wrong.

No doubt about it. But my new skis have made me much more aware of my
problems, and I'm on the right track!

being as heavy as you are a 210 ski will be flat on the snow all the
way.

That's how it was with my old skis. My new skis were special ordered
from the Madshus factory. With all my weight on one, it is almost flat,
rolling my weight to my toes flattens it. This is a big difference from
my old skis that gripped more or less all the time, allowing me to be
very sloppy. Now I have to really concentrate on my rythmn and weight
transfer.

It is almost impossible to find a classic ski today that will give a
person of your weight a good grip to glide ratio.

Glide is very hard for me to judge. On descents I usually have good
speed due to my weight to frontal area ratio, so I glide from everyone
else around, but it is not clear how much drag I have at low speeds
like while DP-ing.

So you should have wonderful grip at any rate.
at any snow conditions.

On snow it is like I am nailed down. Great! On ice, I guess it is my
poor technique that gets magnified.

In climbing a hill on xc skis people tend to lean forward too much.
This will reduce your grip zone
and your grip in general.
Try and put your weight of your upper body on the toe of your boots ins
climbing. This will apply all your 220lbs on your real grip zone.
Also chose your wax well.

;-)

It's snowing right now, and I am preparing for a night ski in a few
hours. Violet Special.

Joseph

rw

Joseph wrote,
Glide is very hard for me to judge. On descents I usually have good
speed due to my weight to frontal area ratio, so I glide from everyone
else around, but it is not clear how much drag I have at low speeds
like while DP-ing.

To test the length and place of glide zone and grip zone there are two
ways of doing it.
1. go to a hill so you can glide. On the way down, lean forward ( if
your grip zone is too long in the front, you will feel it hooking or
slowing)If this is the case start reducing the front grip zone 1/4inch
at a time.

lean backward if it is slowing or hooking do the same at the back.
Normally the back grip zone start under the heel.

2. Go to a shop with a test board and have them mark your grip zone on
your ski.
RW
Went for a skate today it was wonderful nice corn snow. Very fast.

rw wrote:
Joseph wrote,
Glide is very hard for me to judge. On descents I usually have good
speed due to my weight to frontal area ratio, so I glide from everyone
else around, but it is not clear how much drag I have at low speeds
like while DP-ing.

To test the length and place of glide zone and grip zone there are two
ways of doing it.
1. go to a hill so you can glide. On the way down, lean forward ( if
your grip zone is too long in the front, you will feel it hooking or
slowing)If this is the case start reducing the front grip zone 1/4inch
at a time.

lean backward if it is slowing or hooking do the same at the back.
Normally the back grip zone start under the heel.

2. Go to a shop with a test board and have them mark your grip zone on
your ski.
RW

The place I bought the skis did a thorough job of fitting and marking
them. They used a digital deflection micrometer to measure the
deflection for my weight. They also marked the skis individually at the
various deflection depths (0.0, 0.15, 0.1, 0.2, 0.3) fore and aft. And
recommended which one is right and left based on leg measurements. Also
very specific written instructions for which markings to use with what
type of wax, etc. There was a reason I drove 2 hours each way to go to
that store! ;-)

Went for a skate today it was wonderful nice corn snow. Very fast.

Sounds like fun. I just got back from a skate. A dusting of new snow.
Very nice.

Joseph