Climbing Rubber Friction test link


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Social climber
Whitefish Montana
Topic Author's Original Post - Nov 20, 2008 - 08:10pm PT
Interesting link on climbing rubber friction.

Nov 20, 2008 - 08:18pm PT
That's a poor test setup.

Totally static in a controlled temperature environment on a polished smooth slab with nobody in the shoe.

They've always done it this way and it proves nothing except some numbers on a sheet of paper.

Croft could climb in a pair of roller skates that all those rubbers couldn't.

There's your start ......

Trad climber
Norman Clyde's napsack
Nov 20, 2008 - 08:24pm PT
I was about to post the same link. Had the same reaction as you, Werner. Seems contrived to a certain very specific set of circumstances.

I'm such a plonker I can't tell the difference anyway.... 5.10 dot rubber seems best for me!


Trad climber
Lost Wages
Nov 20, 2008 - 08:34pm PT
What about the Acopa rubber?

San Fran Cisco
Nov 20, 2008 - 09:36pm PT
i am opposed to these tests, as, for me, the principal use of climbing rubber is to serve as an excuse.

Trad climber
Nov 20, 2008 - 09:41pm PT
i better go gets some mad rocks... when i flail around i can use this paper as backup to my story.


Social climber
Nov 20, 2008 - 09:44pm PT
Obvious first problem with the test is that it doesn't address deformation of the rubber from having a climber's bodyweight on it.

Maybe a softer rubber with lower coefficient of friction deforms and spreads out more, thereby gaining more contact area than a harder rubber with higher coefficient and thus ends up with higher friction overall.

Second obvious problem is that it only did test runs at a single temperature.

This test is way too simplistic, and looks more like something a sophomore engineering student would set up rather than a CERN guy.


Social climber
The internet
Nov 20, 2008 - 10:06pm PT
A wad of bubble gum would have come out as #1.
Karl Baba

Trad climber
Yosemite, Ca
Nov 20, 2008 - 10:41pm PT
I smell BS as well. Somebody did a rubber coefficient test once and scientifically proved that rubber sticks just as well on wet rock as on dry rock.

I was stunned. Anybody who ever climbed wet rock has got to know the practical difference.



San Fran Cisco
Nov 21, 2008 - 12:22am PT
nah, the (bad) joke was that i need to have the excuse of bad rubber, so that tests would show my excuse to be crap. in fact i climb badly because of a hard gym session the day before.
Mighty Hiker

Social climber
Vancouver, B.C.
Nov 21, 2008 - 12:26am PT
Peter was awful happy when the Fires came out, and took the place of EBs. I'm pretty sure he never tried roller skates - it would be more Canadian to use ice skates. Though they don't get a lot of ice in Nanaimo.

Last >>
Nov 21, 2008 - 12:38am PT
" What about the Acopa rubber ? " I remember seeing a video of John with his own little portable micro-slab for testing shoes . That's been a few years tho .

Gym climber
Mammoth Lakes, CA
Nov 21, 2008 - 03:44pm PT
Wener's right...

This test is absolutely worthless.
Ed Hartouni

Trad climber
Livermore, CA
Nov 21, 2008 - 11:26pm PT
Not sure I'd call it worthless, but certainly limited and only a part of the whole picture.

Wikipedia [url=""]Coefficient of Friction[/url] is not bad on this:

While it is often stated that the coefficient of friction (COF) is a "material property," it is better categorized as a "system property." Unlike true material properties (such as conductivity, dielectric constant, yield strength), the COF for any two materials depends on system variables like temperature, velocity, atmosphere and also what are now popularly described as aging and deaging times; as well as on geometric properties of the interface between the materials. For example, a copper pin sliding against a thick copper plate can have a COF that varies from 0.6 at low speeds (metal sliding against metal) to below 0.2 at high speeds when the copper surface begins to melt due to frictional heating. The latter speed, of course, does not determine the COF uniquely; if the pin diameter is increased so that the frictional heating is removed rapidly, the temperature drops, the pin remains solid and the COF rises to that of a 'low speed' test.

Social climber
Whitefish Montana
Topic Author's Reply - Nov 22, 2008 - 10:56am PT
I posted the original link. The responses got me thinking. I am a physics professor at the local community college.

If the climbers do not like this test. Help me design a test that would satisfy the climbing community. I am willing to take my time and budget to run, document the results, and publish the results on this site.

What I would like is to use this thread to develop some sort of consensus on what you would like for the test. I will then develop a procedure and testing protocol based on the ideas and what is considered standard testing protocols (ASTM maybe?). Then, I will post the procedure on this site for critique, and after review, run the test.

Ed Hartouni

Trad climber
Livermore, CA
Nov 22, 2008 - 11:46am PT
if you read the responses, you can see what most climbers feel are the unmeasured variables in the simple "tilt test" done in that article. Climbers have an empirical notion of what controls friction, and they learn to use that control to achieve the required support for their moves.

 Suppleness of the sole of the shoe.
 Large, flat, smooth contact area.
 Geometry of contact.
 Clean surface.
 Temperature and humidity.
 Type of rock, and surface condition.
 Kinetic coefficient - to - stopping.

These all seem to play some role in "sticking" your feet to the wall. There may be more. As the Wikipedia article said, these variables are "systemic" rather than "material" properties, so it might take a while to investigate.

Also, it might be necessary to actually use a human foot (living) in the shoe to perform the tests. This is because the biomechanical aspects of sticking a foot hold are very important to the use of the shoe, where the shoe's stickieness is only one aspect of shoe performance.

Shoe tests are done with expert climbers who use their experience, and a series of demonstration climbs, to validate the shoe design.

Good luck!

Trad climber
Nov 22, 2008 - 11:59am PT
Ed: "Type of rock, and surface condition"

Yeah, this is really important. A test run primarily on low-friction surfaces (i.e., the two chose for the test you linked)probably tells us less than we need to know about climbing-shoe rubbers.

A series of different surface textures would be more useful.

Gym climber
Mammoth Lakes, CA
Nov 24, 2008 - 12:00pm PT
Ed said,
"Also, it might be necessary to actually use a human foot (living) in the shoe to perform the tests. This is because the biomechanical aspects of sticking a foot hold are very important to the use of the shoe, where the shoe's stickieness is only one aspect of shoe performance. "


Try Formula 1 tire rubber on that test and it will kill all other climbing rubbers - but climbs quite poorly on real rock.

Social climber
Whitefish Montana
Topic Author's Reply - Nov 24, 2008 - 12:21pm PT
After reading several of the reply's. Do people want a way to test shoes or the rubber friction? From John's statements and others as well as my own climbing experience. I know that the system of climber + shoe + rubber = foot sticking on the hold.

Completing a test like was linked in the first post is easy. Trying to replicate a system and get results that mean anything is the tough part.

Thanks for all the comments so far. I am currently looking at the testing literature and lining up students to work on this project. Any more ideas would be helpful.


Trad climber
temecula, ca
Feb 27, 2009 - 11:19pm PT
First of all, All the test claimed to validate was coefficent of friction (COF).Which admittedly is only one aspect of climbing shoe performance. Second, read the test!! The granite was the BOTTOM SIDE of a counter top piece which is much coarser. Third, several of the rubber manufacturers tout a COF test as claim to their products superiority. Fourth, not only will heat, temperature, humidity, weight, contact patch size, angle, and deformation affect performance technique is a major contributor. Rubber design is a compromise of all these variables and may vary according to the style of climbing and type of surface being scaled. you will find that no one shoe or rubber will be suitable for every circumstance. So cool your jets and take the test for what it is and not as a claim of the BEST rubber for all purposes.
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