how skateboard wheels get their durometer values using testing devices.
Testing for “shore” or durometer is a way of measuring the hardness of a material. However, the word “durometer” refers to both the hardness of a material and also to the testing device used to measure it. By hardness, we mean how well a material withstands indentation or changes in shape when a force is applied.
used for determining the hardness of a plastic or rubber is called the Shore Hardness Test
Each durometer scale has a value of 0-100, with a higher number relating to harder material.
Durometer Scales Used
In The Skate Industry
Durometer type Shore A
is widely used for measuring wheels and bushings. Some manufacturers/brands use the type D scale, used for harder plastics, when measuring a wheel’s inner core/hub or outer surface. Recently
, the brands Bones
, Ricta, and others have been using the type B scale for measuring their wheels.
The face of the indicator consists of a graduated dial ranging from 0-100. Durometer scales do not go over 100
, despite products displaying “101A” or greater. Remember
indicates no indenter penetration at all. This means there is no such thing as 101A or 103A. How can there be less than zero penetration?
However, skateboard wheel manufacturers often print durometer values of over 100A on their wheels. Why? Good
Is it marketing hype designed to give consumers the impression their wheels have more durability or better performance?
Or, are they implying the type A durameter tester doesn’t apply enough force to their wheels to accurately measure the surface hardness, and give it a reading above the type A scale? If so, it would be more appropriate to use a type B durameter. They most likely do this to give skaters the impression of what the duro would be if the scale went over 100A.
Durometer Reading Variations
Typically, the durometer value printed on a skateboard wheel is not actually the true durometer. Street skating
wheels labeled 100A could actually be something quite different, such as 97A, or even 95A.
factors can affect how the durometer reading of a urethane wheel is different than what is printed:
1. Time- While pouring material into molds, and material curing time.
2. Temperature- Of material, atmosphere, and mold.
6. Marketing hype
The durometer value printed on your wheels should match as closely as possible to the wheels’ true durometer. Here’s why:
wheels are faster on smooth surfaces.
2. Harder street skateboarding wheels typically resist flat spotting.
3. Harder wheels slide/drift easier.
4. Softer wheels have more grip on the road.
5. Softer wheels are faster on rough surfaces
6. Softer longboard/downhill skateboarding wheels typically wear less.
Converting Durometers A and B Scales:
has recently been using the type B scale. Bones states, “It is very similar to the A Scale
, but reads 20 points lower, allowing the useful scale to be extended by 20 points, which covers the entire hardness range of skate wheels in one scale.”
This is not entirely true. Although, the B scale does read lower than the A scale, it is important to note that a measurement on the A scale does not directly convert to 20 points lower on the B scale. A durometer reading of 98 Shore A should not presumably be 78 Shore B.
At the Bones Wheels website, (http
://bones.com/why/b-scale/), they have a comparison chart indicating that 103A is compared to 83B. This is not accurate. The Bones comparison chart appears to be arbitrarily constructed and not based on acceptable industry comparison charts already in use. Comparison
charts are used for reference, and all testing should be done using a separate type durometer tester.
tested Bones STF
83B wheels with both type A and type B durometers. Our results were 97A and 98A , and 74B to 83B. Not only did this show that the Bones STF 83B wheels being tested are not 103A (as if the A scale actually reached 103A), they are not even 83B, regardless of the rare wheels (not sets) that actually tested at 83B. In fact, some tested as low as 74B, which is 9 points less.
We commend Bones Wheels for its leadership in the skate industry in switching to the Shore B scale. (BUT they failed to provide accurate durometer readings, and a bogus comparison chart.)
We would like to know your thoughts about the B scale, especially after what you have read. Please
post your comments below.
- published: 30 Jun 2015
- views: 51656