For street skating you want hard, small wheels, roughly 99a to 101a in hardness and 50-54 mm in diameter; for getting around town or cruising you want soft, larger wheels, around 78a to 87a and 55 mm or more. Those two numbers, the durometer (hardness) and the diameter in millimetres, are the only ones you truly need to understand to buy the right set. Everything else is fine-tuning.
Hardness: the A scale (and the B scale)
Hardness is measured with a durometer and written as a number followed by a letter. The vast majority of wheels use the A scale, which in practice runs from 78a (very soft) to 101a (very hard). The higher the number, the harder the wheel.
Some brands, notably Bones with their skatepark line, use the B scale to measure urethane harder than 100a accurately. The B scale reads 20 points below the A scale, so an 84b wheel equals 104a, and an 80b equals a classic 100a. It isn’t a marketing gimmick: above 100a the A-scale needle loses reliability, and the B-scale gauge reads that rock-hard urethane without puncturing the surface.
| Durometer | Feel | Best for |
|---|---|---|
| 78a – 87a | Soft, lots of grip | Cruising, city, rough ground |
| 88a – 95a | Middle ground | Mixed street + cruising, beginners |
| 96a – 99a | Hard with some grip | All-round street and park |
| 99a – 101a | Very hard, fast and slidey | Street, skatepark, ledges and rails |
| 83b – 84b (≈103a-104a) | Extra hard | Concrete skatepark, fast bowls |
Diameter: top speed versus acceleration
Diameter is measured in millimetres and sets the trade-off between top speed and acceleration. A smaller wheel spins up faster, so it accelerates quicker and weighs less, which suits technical tricks. A larger wheel holds speed better and rolls over cracks and grit without catching, but it takes more effort to get moving.
- 50-53 mm: pure street, technical flip, ledges. Where most skaters live.
- 54-56 mm: the all-round middle, street and park at once. If in doubt, start here.
- 56-60 mm: park, bowls, transition and fast mini-ramps.
- 60 mm and up: soft cruiser and longboard wheels, built for covering distance.
Contact patch and shape
The contact patch is the area of the wheel touching the ground. A wide patch gives more grip and stability; a narrower one breaks into a slide sooner, which many skaters want for slides and powerslides. The edge shape (conical, classic, radial) fine-tunes this: conical profiles offer less side friction, rounded ones more grip. It’s not a make-or-break decision when starting out, but it explains why two wheels of the same durometer can feel different.
Flatspots and why hard urethane resists them
A flatspot is a flat patch that forms when a wheel locks up and drags across the asphalt, typically in a powerslide or when you catch a foot. Once a wheel has a flatspot it vibrates and hums on every rotation, and there’s no fixing it. High-quality, harder urethane resists this wear far better, which is why premium street wheels like the Spitfire Formula Four are so respected: they hold their shape and speed season after season. Soft or cheap urethane wears down and flattens much sooner.
Street, park or cruising
- Street: 99a-101a, 52-54 mm. Prioritise slide, low weight and flatspot resistance.
- Skatepark / transition: 97a-101a or 84b, 54-58 mm. A touch more wheel to hold speed in the bowls.
- Cruising / commuting: 78a-87a, 56-60 mm. They soak up rough ground and roll smoothly over cobbles and old asphalt. Brands like OJ specialise in these soft ranges.
If you switch to big, soft cruiser wheels on a street deck, watch out for wheelbite (the wheel rubbing the deck when you turn): you may need to add riser pads.
Frequently asked questions
What wheel hardness is best to start with?
If you skate street and skatepark, 99a wheels in a 53-54 mm size are the safe, standard choice. If your main use is getting around town, go for 78a-87a.
Can I put soft wheels on a normal street deck?
Yes, within a size limit. Up to about 56 mm is usually fine; above that, add riser pads to avoid wheelbite. You’ll gain comfort on rough ground at the cost of a little flip response.
How many wheels come in a set and how often do you replace them?
Sets come in fours. There’s no fixed lifespan: replace them when they wear unevenly, develop a flatspot or lose too much diameter. You can compare prices for wheels and complete setups in the catalogue.