With some wheels it's very difficult to enter the slide, resulting in the urethane getting caught up and skipping and chattering along the asphalt and, with other wheels all grip will be suddenly lost and slip out entirely. What makes a wheel good is its consistency during and while entering and leaving a slide, as well as its grip. A good wheel makes you feel you always have constant and consistent feedback and control, whether you are apexing a corner or in the middle of a slide.
For years I skated on the legendary Hypers, mostly on the Hyperformance +G, which are still being used by many downhill (DH) riders. I tried so many wheels when Hyper stopped making them, and now what they manufacture has nothing to do with the real HYPERS back then. Even their newly manufactured Hyper Concrete +Grip, that now come in multiple colours, bear the same name, but the urethane compound is NOT the same; it's no longer the same company.
This brings us to durometer (aka, hardness), durability (how fast a wheel wears down), and urethane compound. Generally, a durmeter range of 83-86a is preferred, but not all wheels of the same durometer are equal, even between batches of the supposed same wheel from the same manufacturer, due to the differences in the urethane compound. Also, in general, it is understood that the higher the durometer, the less grip that a wheel has. Again, this is not always true, as some higher durometer wheels have a higher level of grip than lower durometer wheels, due to the specific urethane compound. Regardless of grip, within the approximate range of 83-86a, the most important aspect of a wheel is the consistency of its grip and the consistency of the slide. A quality urethane will provide a smooth transition into and out of a slide and will not result chattering along the asphalt or a sudden slip out from grip to no grip. For the most part, going too high in durometer - 88a and higher - will result in a wheel that suddenly transitions from grip to no grip and slips out and going to low - 82a and lower - will result in a will that will wear quickly and may dig in due to the heat and friction of a slide, combined with the low density of the wheel. Of course, there are some exceptions to every "rule."
In a quality wheel, the urethane will not become soft under the heat and friction of a slide and dig in; its grip, slide, and wear level will remain relatively constant and predictable.
My favourite Wheel is Hydrogen 84mm. The 80mm and the 90mm act differently, especially the 90mm which has much more traction and is harder to enter the slide. The same model from the same manufacture can behave differently in each size, due to the different hub/urethane ratio.
Regarding wheel size, especially if you are still learning, do not go more than 80mm-84mm. About the big wheel craze, I will write about this in the next article. Remember, most of the wheels when they are brand new, are harder to enter the slide, due to the smooth outer coating of the finished wheel. So, if you have no patience, do some t-stops to wear them down a bit. Speed is your best friend. Most of the people who send us videos are entering the slide to slow! I know that it's easier said then done, but go faster. Don't forget to rotate the wheels so that they last way way longer. *Thank you to Mike Rensmaag for helping with the article .