@3:46 this is a very common misconception, that rubber follows Coulomb's law of Friction Force, meaning that the friction force is not a function of the area of contact. In reality, with rubber and other soft materials you cannot apply this law, it simply does not hold true (well, it holds true if you consider that the friction coefficient is not a fixed value, but a function of the contact area). Rubber has a much more complex physics behind how it generates friction. The rubber is conforming to the surface and mechanically locking itself to the small imperfections/indentations of the wall/rock, and the bigger the surface of contact, generally the higher the friction - this without discussing the more complex 'adhesive' phenomena of the attractive forces between the rubber surface and the rock, that happens on a micro-scale. Just look at racing cars - they wouldn't use those fat and wide tires, which are part of the unsprung mass and VERY heavy, if they could get away with using skinny small tires and generating the same amount of grip (friction force). The friction goes down with the smaller contact patch of rubber! Great video! I really liked how you moved your feet, making the contact patch smaller and smaller, until it slipped, great practical example Josh!
Thank you for the comment! Good to see it written out in a bit more detail. I'll have to copy and paste next time we get comments saying surface area doesn't matter :D
it's an important concept. We might add that another important piece for tires actually relates to what is said in the video about the rubber failing. Wider tires are also associated with grip because of the basics of coefficient of friction, in that you get more friction from a softer compound. . .which is not as strong and so must be wider to not fail under the same weight. This is important when choosing tires --- people who just think wide tires are cool might choose a wider size of the exact same tire and get no benefit as they really do just spread the friction and not change it (see USA motorcyclists), when what they want is a softer racing tire that is also necessarily wider so it doesn't fail.
@@mikemoore-hehim1149 hah indeed! If you go to Nürburgring you'll see this all over the place. Little underpowered cars with big wide summer tires with hard rubber, thinking they are improving performance with wider tires - I bet they can never get those tires up to temperature to get the best out of them. In that case, getting more surface area will actually hinder performance! The temperature plays a big role. I always wondered if we should be doing the equivalent of a burnout (I mean, warming up the rubber of our shoes) before we get in a hard boulder project 😅. But I found out that the composition of the rubber of most shoes is already optimized for it to get the most friction at the lower temperatures that the climbing shoes are subjected to; if we did a warm up the rubber of the shoes too much, the rubber would just crumble. Nevertheless it sure helps to warm them up a bit in winter before getting up a slab! Specially in the dead of winter in Fontainebleau! If you take your shoes out of the bag at 0°C you can feel that the rubber if somewhat glassy and has poor friction. If you just slap them into your feet and quickly jump into a slab you will have a bad time!!! In winter, before I start climbing I normally I put my shoes inside my shirt close to my chest, just for them to get as warm as my body, before I put them on my feet (I have cold feet). I guess this is my climbing-equivalent of a burnout 🤣
@@satanaz I did this a lot in the winter (warming my shoes up inside a vest or jacket), because putting on cold shoes an then climbing hurt my feet, and started noticing that it doesn't just hurt less, it feels so much better to climb in slightly warmer shoes. Now I know the physics behind that, so thanks for the lesson I guess!
ngl its so funny how people STILL use downturned shoes while slab climbing and wonder why they cant get maximum contact with the wall or holds lmffaaooo
Absolutely fantastic video can't wait to get back in the gym and try out some of these tips. Always enjoy slab climbing but I am way worse at slab boulders compared to any other type.
I just started climbing a little while ago, and this video made me realize how unflexible my hips and hamstrings are, Definitely something i have to work on more to do this kind of stuff 👍
The section on edges helped me really understand the importance put on balance. I will use this as a lesson to incorporate more balance of strength, which I tend to resort to out of frustration. Thank you for the eye opening demonstration!
am i missing something? in all the videos of climbing on outdoor slab the heel never goes "down" rather the toes are bent much more increasing the contact on the front of the bottom of the foot. it looks like for a brief moment the heel is down but not being engaged until the hips are much higher and rather when the foot is above the hip the edge of the shoe is being utilized.
I think its not uncommon, slab is more technique dependent than other types of climbing, so if ones strength is lacking, then they might be able to climb harder slab than other styles. Obviously there is some strength component to slab (pistol squats, crimp strength), but its typically less than what's required for say a roof climb of the same grade.
Great vid! I had a some bad slips on the wall and this video really helped me understand why it was happening. I was blaming the shoes 😂but now know better! Thanks☺
The way I see it with the rubber contact thing is that while there may be some small contribution of contact area (I don't know much about materials), we're missing a big factor here which is the biomechanics of your leg and how you can apply force to the wall. At a basic level, max static friction is the coefficient of friction times the normal force. The normal force being the force you apply perpendicular to the surface. With a low heel, you push more directly into the wall. As soon as you lift up your heel, your legs move and your resultant force starts to angle downwards. Pausing the video at the start and end of the demo shows this very clearly, the angle of your shin is a good standin for the angle of your force on the wall and that changes a fair amount. So your overall friction, assuming a coefficient of, say, 0.4, would be 0.4*cosine(angle from the horizontal)*F, BUT you also have to contend with sine(angle)*F additional downwards force which is going to contribute to you wanting to slide. So you have less friction and more pulling (pushing?) you down that that friction has to fight against. If you wore shoes that had a bendable toe and you repeated the experiment my belief is that you would still have the same point of failure even with a whole toe's worth of rubber on the wall. As a climber, I try to think about pushing perpendicular to any surface where I'm worried about slipping. I find that helps more with my footwork than just "heels down" because it encourages more force on the wall, and it integrates well with the stuff Anna was talking about with keeping your feet high so it's kind of an all-encompassing philosophy. edit: just an addendum - notice how at 1:11, Anna has a small contact area yet she is still staying on the wall. But when she stands up later she slides off, even though she has the same (or possibly slightly more) contact area. The difference being her force direction :)
The direction of the force you apply to the foothold is based on where your center of mass is in relation to the support (the foothold). If your hips are right above the foothold, then your force is vertical no matter if you drop your heel or not. The angle of the contact area is constant as the foothold is unyielding. As you say at 1:11 she stays on even if the surface area is low. This is because she moves her center of mass so far away that almost all her force is normal to the foothold. If the handholds were worse, and she had to move her center of mass closer to the wall, then the shear force would increase, and more surface area would be necessary to not shear of the rubber.
I'm having a LOT of trouble with the hip flexor exercise at 8:20, anyone know an easier variation? I can lower the platform but the movement is still very hard to control, I often lose balance, and sometimes it hurts :(
Hi thank you for the video. At 3:13 you said that the wall doesn't have texture, just normal paint. I am on the way to make my own climbing gym at home. What would you do it. Textured wall. Or regular paint? I am doing it for my kids and I. Thanks
More force on smaller area of rubber doesn't equal same friction force.. as load increases on rubber the coefficient of friction drops, essentially its less efficient.. well this is true for race car tyres anyway, it will be the same for climbing shoes otherwise all the top racing teams would be knocking on the door of all the climbing shoe company's 😅 your better of spreading the load over a greater area and maximizing the coefficient of friction of the rubber!
Thank you both SO much for your tips!!! You guys are really great at explaining things in a straightforward way. Cant wait to put these drills into my practice!
😄 this is Luna, Border Collie, and she is the is best! Her favourite games include fetch and hide the toy (she is very clever and knows them by name). She likes belly rubs in the morning and running through open fields.
Yes I sometimes do barre training with my clients on flexibility training plans. We make a similar set up using a barbell in a cage. I've not tested dancers but I would assume they score better than the average climber.
Yeah they are the new Evolv Shaman 3’s. Coincidentally, I’ll be getting myself a pair in the next couple of weeks so I guess I’ll have no excuses for ignoring those slab routes 😅
also on several outdoor climbs the Evolv Oracle is shown though no longer in production since the release of the newer Shaman line. She is using the standard volume of the Shaman in the gym.
People who make the argument about smaller contact, greater pressure forget that coefficient of friction ignores static friction and van der waals forces. It's wrongly applying an idealised physics limit. This is why F1 cars have broad tyres.
I'm not a physicist so happy to be proved wrong. But I'll paste the comment from another viewer that makes sense to me (and why surface area does matter)........... "this is a very common misconception, that rubber follows Coulomb's law of Friction Force, meaning that the friction force is not a function of the area of contact. In reality, with rubber and other soft materials you cannot apply this law, it simply does not hold true (well, it holds true if you consider that the friction coefficient is not a fixed value, but a function of the contact area). Rubber has a much more complex physics behind how it generates friction. The rubber is conforming to the surface and mechanically locking itself to the small imperfections/indentations of the wall/rock, and the bigger the surface of contact, generally the higher the friction - this without discussing the more complex 'adhesive' phenomena of the attractive forces between the rubber surface and the rock, that happens on a micro-scale. Just look at racing cars - they wouldn't use those fat and wide tires, which are part of the unsprung mass and VERY heavy, if they could get away with using skinny small tires and generating the same amount of grip (friction force). The friction goes down with the smaller contact patch of rubber! Great video! I really liked how you moved your feet, making the contact patch smaller and smaller, until it slipped, great practical example Josh!"
You just have to look at all the rubber marks in a climbing gym to know that shoes slip not just because of a lack of friction, but because of shearing the rubber surface. Increasing surface area decreases shear stress
