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Rock Climbing : Comments

Comments by Chema23 (1)


Article: Climbing Rubber Friction Test
Markmello,

Rubber has many properties that contribute to friction: adhesion, abrasion resistance, and shearing resistance to name a few. Of course there are factors such as temperature, shape, and magnitude and duration of pressure that will affect climbing shoe performance as well, but for now I'll stick to the properties mentioned which are specific to a particular type of rubber.

Adhesion is how sticky or tacky the rubber feels, this is good for showing off your shoes by hanging one off the edge of another (if you've never done this it's really cool, take two brand new shoes with super clean edges, warm up the toe a bit by rubbing them together or against your hand, then press the toes together really hard and let go of one shoe, it should hang off the other for a moment). Apart from that, and collecting chalk and dust, that's about all adhesion is good for, oh and probably holding 15oz. on an incline. See, adhesion is useful when not much force is involved, and it's usually what people think of when they think of friction. I mean, chewing gum is really sticky, but wouldn't make good climbing rubber.

Abrasion resistance, now we're talking. This is the rubbers ability to not smear off its outer layers. Gum might be able to hold a piece of paper upside down, but put gum on the toe of your climbing shoe and you better believe it will decrease your shoes performance. This is like stickiness for grown ups, you notice it when there's a lot more pressure being applied. I am over-simplifying it though, because steel is highly abrasion resistent, but it won't make you stick to the wall better, and than's because it's too hard. The rubber needs to be soft enough to conform to the texture of the wall under normal climbing loads (anywhere from a couple to a couple hundred pounds, depending on how hard you're pushing of course), but hard enough to not abrade away when the loads get toward the higher end.

Shearing is when big chunks are taken out, and this is why edges taper in. If climbing shoe edges flared out (so that it would be easier to get your edge on that tiny crystal), the flared edge would just tear off. You've probably noticed that you get little ribbons of rubber running along the edge of new shoes after just starting to climb (I always tear them off compulsively), that is shearing at work. You can think of shearing as the big brother to abrasion. Just as adhesiveness deals with really small amounts of weight and rubber, and abrasion deals with larger amounts, shearing deals with even larger amounts.

ok i'm tired of writing, I hope that made sense, and seemed relevant.

Cheers,
Chema