Bones® Wheel Formulas Explained

bones wheels logo

Back in the late 70’s and early 80’s Powell Peralta started developing the best skateboard wheels ever offered to skateboarders around the world. This legacy continues today with the company offering several different formulas and options. This will allow you to fine tune your set up for whatever terrain you are riding.

Bones is the trademark name Powell Peralta uses for their most of their wheels, bearings & accessories. It is named after one of their first high profile team riders Ray “Bones” Rodriguez. Ray was one of the first pro riders for Powell in the late 70’s. His famous ‘Sword & Skull’ graphics is credited for crating a whole new look and direction for graphics from that point onwards. The name Bones first appeared on skateboard wheels around 1977 and they have been on the market ever since. Over 40 years later Ray “Bones” Rodriguez still rips and his personal signature wheel is available.

You may have heard of Bones STF and SPF wheels and are unsure what that means. The different urethane wheels can all look the same but what is the difference? The diameter of the wheel is pretty straight forward, but what do the numbers that indicate the hardness like 99A and 83B really mean?

Below is a detailed explanation of Wheel Formulas to help answer those questions and select the perfect wheel for your skateboard.

BONES WHEELS® STF Street Tech 103A Formula®

Street Tech 103A

BONES Street Tech Formula (also known as STF) are wheels that roll fast, grip when you need to and slide when you want to, without flat spotting. STF gives you more control to skate with confidence.

BONES STF wheels outperform all other wheels, and because they wear so well, they can last several times longer than normal wheels, making STF wheels great value for money. BONES STF wheels are available in the original 103A / 83B. If you are looking for a wheel that is a little more forgiving check out the new 99A Easy Streets™ for greater roll, control and softer landings on rougher terrain.

BONES WHEELS® STF Easy Streets™ 99A Formula

 Easy Streets™ 99A

BONES WHEELS Easy Streets are softer 99A Street Tech Formula wheels that ride smoother and faster on a greater range of terrain, without loosing the unique grip, slide-ability and characteristic bark of our original BONES 103A / 83B STF.

Easy Streets will improve your skating if you are not always riding super smooth concrete. They make it more fun to skate a wider range of terrains by cushioning your landings, gripping, sliding, and rolling easier on rough pavement…without flat spotting.

BONES WHEELS® SPF Skatepark Formula™

Skatepark Formula

BONES Skatepark Formula (also known as SPF) is very high quality urethane that clocks in around 104A / 84B. It is specifically formulated to resist flat-spotting on slick or smooth surfaces while maintaining a higher rebound for a quicker response and a faster roll.

Skatepark Formula has a high resistance to abrasion while not compromising hardness and slide ability. Simply put… BONES Skatepark Formula grips better on slick surfaces, are almost impossible to flat-spot, and are the fastest, longest lasting wheel on the market today.

You won’t find BONES Skatepark Formula from any other wheel supplier so get a set and find out for yourself what the word on SPF is all about.

BONES WHEELS® ATF All-Terrain Formula™

 ATF All-Terrain Formula

BONES All-Terrain Formula wheels are poured in a special soft urethane we call All-Terrain Formula or (ATF). ATF wheels are excellent for rougher terrain so regardless of road quality, this revolutionary formula will roll you there quickly and smoothly.

All the information above explains the difference between all the Bones formulas. The durometer or hardness of wheels is a very technical area. We are constantly asked about what it means and which wheels are best for you. I’ve scoured the interwebs and come up with a bit of information below to help you get a snap shot into this fascinating area of engineering.

How hard are your wheels? The DUROMETER SCALE explained.


The Shore Durometer Scale is a system is used for measuring the hardness of different materials. There are several different scales, the most common to use for skateboard wheels are the A and B scales. Urethane hardness is measured with an instrument called a Durometer. The durometer instrument features a gauge with a needle that is pushed into the urethane wheel. The depth the needle depresses the urethane gives a reading on the gauge indicating the material hardness.

measure skateboard wheel hardness

Most commonly used is the A scale is and it is best for softer compounds. The B scale gives a more accurate hardness reading for harder wheels. The A scale goes from soft to hard indicated with a number between 1 to 100. Materials over 95A are difficult to get an accurate reading on. They are best measured with the B scale.

The Shore Durometer B Scale is perfect for harder skate wheels because it is very similar to the A Scale. It reads 20 points lower. Therefore the useful scale is extended by 20 points. It covers the entire hardness range of skate wheels in one scale.

The B scale uses the same soft spring as the A Gauge. The B scale uses a different shaped conical gauge needle also used for the D Scale. Because the spring is soft, the sharper D Scale gauge needle does not puncture the skin of the harder wheels surface. This gives a more reliable reading with harder compound skateboard wheels. The D scale is used for measuring the next level of materials that are much harder.


So there you have it. Need some new Bones or Powell Peralta tyres? Click here.