Concave is a major factor in board performance. Skateboard manufacturers are always experimenting with new concave shapes to accommodate new types of skateboarding. Most concave shapes allow riders more foothold than a flat skateboard, which can take sliding, drifting, and turning to the next level. Here are a few of the main types of deck concave.
This concave shape may look familiar to you. The subtle U-shaped curve is the most common deck shape, though some boards have a deeper curve than others. This type of concave allows your feet better grip, which can be useful in nearly all styles of skateboarding.
This shape is a similar but more dramatic version of the radial concave. The steep wall on the rail combined with the wider base allows more secure footing and a more locked-in feel.
The W-shape does not extend the entire length of the deck, just the area towards the tail. The extra curve in the centerline allows you to shift more energy from your heel to your toe. The result is a highly precise, responsive board that can turn quickly.
Tub concave (also called flat-cave) is similar to a radial board, but instead of a gentle curve, the rails extend at a sharp angle from the deck. Tub boards keep your feet flatter, which makes for a mellower ride, but the sharp rails can still provide sudden shifts in energy.
Asymmetrical concave is when the skateboard's rails rise at different angles. This allows riders more power in their heels for turns.
Convex boards feature an upwards-arching deck. They are uncommon, though some slalom and downhill skateboarders love the more natural foot placement convex boards provide.
Skateboard decks with no concave are rare, with the exception of reissue old school decks. Some cutout and dropdown longboards also feature flat decks. They allow lots of space for your feet, and allow room for boardwalking and other showy tricks.