Big BMX/Freestyle Glossary

A rim profile that lacks a flat braking surface – instead, the rim is smoothly rounded into a teardrop shape. Because of this, caliper brakes will not work on it. It is primarily used on the front wheel for better aerodynamics, weight savings, and a clean look, or by riders who prefer a brakeless style.

A traditional type of headset with cups that must be pressed directly into the frame's head tube. It uses loose ball bearings. Today, you'll find it mostly on kids' bikes or entry-level models. For more advanced riders, the modern integrated headset is the standard.

A basic obstacle in a skatepark. It is a flat inclined surface (without a curve) used for jumping off to perform tricks or as a softer landing area.

A crucial safety feature. Plastic or aluminum plugs that are inserted into the ends of the handlebars. They prevent serious injury (puncture wounds) during a fall onto the bar ends. Riding without them is universally banned at skateparks.

A protective shield integrated directly into the sprocket body. It protects the teeth and chain from getting destroyed during botched tricks or intentional grinding over the bottom bracket (sprocket stall).

The bearing system in which the crank spindle rotates. The most widely used standard in BMX is the Mid BB (bearings pressed directly into the frame). There is also the smaller Spanish BB and the threaded Euro BB (common in Race BMX).

An artificially created pool in a skatepark made up of connected radiuses. It is completely enclosed and ridden to gain speed and maintain a smooth flow.

The riding style without mounted brakes. The bike looks cleaner and the cables don't get in the way during barspins. Stopping is done by pressing the shoe sole against the rear tire, which requires anticipation and quality shoes.

The foundation of all Freestyle BMX. It involves jumping into the air on flat ground without the use of any ramp. The rider first pulls the front wheel up, then jumps with their legs to pull the rear wheel up. Most tricks evolve from this basic movement.

An advanced technology for manufacturing frames and handlebars where the tube wall thickness varies. Near joints and welds, the tube is thicker for maximum strength, while the middle is thinner to save overall weight.

A classic rear hub where internal pawls ensure instant engagement when pedaling forward. The trade-off for this quick engagement is that when riding backwards (fakie), the cranks spin and the rider must pedal backward along with the bike's motion.

A method of precision manufacturing for components (typically sprockets and stems) using computer-controlled routers from a solid block of aluminum. These parts are extremely precise, strong, and allow for intricate designs.

A seat that is permanently attached to a short seatpost as a single piece from the factory. It is an extremely lightweight and affordable solution, but the tilt angle cannot be adjusted.

The circular steel tube lining the top edge of a ramp (radius). It forms the transition between the radius and the deck, making it easier to perform grinds and technical lip tricks on the edge.

The most important parameter when selecting components. CrMo is a high-strength alloy steel used for pro BMX parts (they are lighter and extremely durable). Conversely, Hi-Ten (High Tensile) is a cheaper, softer steel suitable mostly for recreational riding or kids' bikes. Katmar.cz always recommends CrMo for hard impacts.

The distance from the center of the bottom bracket to the rear axle. A shorter rear end (e.g., under 13.2") makes the bike extremely responsive, easier to manual, and faster to spin – ideal for street. A longer CS (over 13.5") ensures stability in the air and at high speeds on dirt jumps.

A rim constructed from two walls separated by a hollow chamber. Compared to a basic Single Wall rim, it is much stiffer, stronger, and better resists impacts from under-rotated tricks.

The small cog (usually 9 teeth) with its own bearings and pawls, integrated directly into the hub body. With the massive shift towards micro-gearing, it replaced the old, bulky screw-on freewheels.

View Drivers

The ends of the frame or fork where the wheel axles are mounted. They can be laser-cut from CrMo steel plates or cast into shape (Invest Cast) to achieve maximum strength for grinding tricks.

An older and smaller bottom bracket standard, characterized by bearings pressed into aluminum cups which are then threaded into the frame. It has been replaced by the press-fit Mid BB in modern Freestyle BMX, but remains popular on Race BMX bikes.

The basic movement of riding backwards on the bike (e.g., after coming down a ramp or completing a 180° turn). While going fakie, the rider must maintain balance and then hop or pedal-pressure out to face forward again.

A Male axle is a traditional solid axle with external threads that protrudes from the frame/fork and tightens with a nut. A Female axle is a thick hollow axle flush with the hub. The hub is secured using bolts that thread through the dropouts directly into the axle (a cleaner design, sturdier, and you won't scrape your ankles).

Refers to BMX grips lacking the inner protective rubber disc (flange). They are by far the most popular choice for street riding, as the flange won't get in the way when catching the bars after a barspin.

A specific BMX discipline resembling figure cycling. It takes place on a smooth, flat surface with no obstacles. The rider performs complex balancing tricks using a specially designed bike (very short frame, zero-offset fork, long knurled pegs, and a freecoaster).

A deep training pit filled with foam blocks. A launch ramp leads into it, serving as a completely safe environment to practice double backflips or heavy rotations before taking them to a hard surface.

A manufacturing method for aluminum parts where material is pressed into shape under immense heat and pressure. This process compresses the metal's structure, giving parts (like stems) high toughness and resistance to snapping.

A type of rear hub with an integrated internal clutch that physically disengages the drivetrain when moving backward. This allows the rider to go fakie without the cranks turning – offering massive creative freedom for balancing. It does require specific maintenance and getting used to the "Slack".

The two basic stem designs for holding the handlebars. With the older Front Load style, bars are clamped from the front, keeping the overall grip lower. The currently dominant Top Load clamps from above – naturally raising the cockpit height, improving the rider's stance, and saving their back.

Defines a rider's natural stance. A "Goofy" rider grinds on the same side they normally spin towards (e.g., grinding on the right and spinning 180° to the right). Normally, riders naturally cross these motions.

A grind is a trick that involves sliding along ledges or rails. It is mostly done using mounted steel or plastic tubes on the axles (pegs). If a rider takes the pegs off and slides directly on their aluminum pedals or dropouts, this clean style is referred to as "pegless".

A special steel plate welded to high-stress areas of the frame (typically on the top or bottom tube right behind the head tube). This reinforcement prevents the head tube from ripping off during extremely hard front-end landings (nosedives).

A special chain composed entirely of links that function as both inner and outer plates simultaneously. The main advantage over a standard chain is the ability to shorten it in smaller increments (literally by half-links). This allows you to perfectly dial in your rear wheel position in modern, ultra-short dropouts without the chain sagging.

The parameter determining the angle of the frame's head tube, which fundamentally affects steering. A steeper angle (e.g., 75.5° and higher) brings the front wheel closer to the frame, making the bike twitchy and better for front-wheel tricks. A mellower angle (e.g., 74.5°) provides great stability at high speeds and confidence over big jumps in the park or on dirt.

A manufacturing process for high-end CrMo forks, frames, and handlebars. After welding, the component is placed in an oven for a controlled heating and cooling (hardening) process. This relieves internal metal stress and increases the material's strength by tens of percent.

An essential accessory for riders running pegs. It is a plastic (slides easily) or metal shield installed on the hub axle between the peg and the fork/frame. It effectively prevents grinding away the hub body or cutting through expensive spokes on concrete ledges.

Today's absolute standard across all Freestyle BMX bikes (from advanced beginners to pros). The frame is machined from the factory with 45° bearing races inside the head tube. Sealed bearings (SB) just drop right in by hand. No pressing cups, easy and fast maintenance.

A weld-free component manufacturing technology, also known as lost-wax casting. Primarily used to make dropouts on high-end frames and forks. The dropout is cast as one solid piece of material, eliminating weak welds and naturally, cleanly blending into the steel tubing.

Abbreviations defining which side the sprocket and chain are on. RHD (Right Hand Drive) is the traditional right side. LHD (Left Hand Drive) moves the chain to the left side. It is chosen primarily for grinding: if you like sliding on right-side pegs, an LHD drivetrain keeps your chain safe from getting caught or snapping on ledge edges.

A special stiff brake cable housing. The inner steel wires are not coiled like in mountain bikes; instead, they run straight and parallel. This ensures that when the housing twists around the steerer tube (e.g., during a barspin), it doesn't change length and the brake won't accidentally lock up.

A pillar of technical riding. A Manual is riding smoothly on just the rear wheel, maintaining balance through body weight without pedaling. The opposite is the much harder Nose Manual, where the rider shifts their center of gravity to the front wheel while riding and balances the rear in the air. These tricks act as links between other elements in long combos (lines).

By far the dominant bottom bracket standard for Freestyle BMX frames today. These are quality sealed bearings (SB) of a specific outer diameter that are pressed straight into the frame tube from both sides using a mallet and wood, or a press. To ensure compatibility with your cranks, you only need to match the inner hole of the bearing to your spindle size (19mm, 22mm, 24mm).

A very sensitive geometric parameter – the distance from the front wheel axle to the imaginary center line of the fork tubes (how far "forward" the wheel sits). A short offset (e.g., just 22 or 25 mm) brings the wheel closer to the rider, maxing out steering responsiveness and making front-wheel tricks easier. A longer offset (up to 32 mm) tracks straighter and is used for dirt jumping to provide more calm on landings.

Refers to performing a trick on the rider's unnatural or "weaker" side. If you normally spin 360s to the left and grind on the left, doing those tricks on the right side is called Opposite (or Opp for short). It is used to clearly denote increased difficulty for higher-level technical riders.

An active riding discipline and environment made of artificial obstacles (mostly wood and concrete). Park riders prefer very light and short bikes equipped with a gyro and narrower tires to give them the necessary speed on plywood or concrete transition for high airs.

A hollow cylinder installed on the front or rear axle, primarily used for grinding. Traditional tubes for raw street are forged from CrMo steel. However, they are increasingly being replaced by plastic pegs featuring a light alloy core and a thick nylon sleeve that won't damage skatepark coping and slides much better on concrete.

Innovative seat mounting systems that unified the BMX world. Forget about old steel rails. A Pivotal seat secures firmly to the seatpost via a toothed joint with one heavy-duty hex bolt accessed through a slit in the top of the seat. The Tripod system mounts without a visible bolt from underneath and looks extremely clean, though it offers less freedom for fine-tuning the tilt angle.

A fundamental quarter-circle obstacle in a skatepark that, depending on its height and steepness, shoots you into the air or sends you back down fakie (if you don't air it completely). The very top is finished with a deck and a steel tube coping for technical tricks.

An ingenious, sophisticated mechanism mounted under the stem on the fork steerer. It consists of a moving bearing with cups where the upper cables from the brake lever lock in and the lower cables to the rear brake exit. This gives the rider the ability to spin the handlebars 360 degrees endlessly (for barspins or tailwhips) with a fully functional brake, without fear of tangling and snapping cables.

A proven standard of high quality in BMX parts. The abbreviation stands for a high-quality sealed industrial bearing equipped with protective dust shields. The bearing holds grease stably inside, resists sand and water, and rolls super smooth. It requires zero maintenance until it wears out – at which point the whole thing is knocked out and replaced. We highly recommend these bearings.

A crucial characteristic of freecoaster hubs. Think of it as a "gap" or dead zone when engaging forward. When coming out of fakie and pedaling forward, you must rotate the cranks, sometimes up to a quarter turn, before the clutch inside the rear hub engages and the bike drives forward. A larger slack protects you from accidental engagement at the wrong moment, which could throw you off the bike. It can be tuned by adding washers inside the hub.

Two radiuses placed back-to-back. They are not separated by a deck like a Funbox, but share one narrow rough platform or two copings. A heavy and visually striking obstacle for technical tricks, requiring you to land over the edge onto the other side.

A sprocket mounting system for demanding riders. It relies on the absence of an attachment bolt. The sprocket has a solid steel inner insert that perfectly matches (tooth for tooth) the splines on your bottom bracket spindle (typically 48 splines). This eliminates the risk of snapping a small locking bolt on an aluminum crank, and driving force is distributed across the entire spindle.

The toothed drive "plate" on the front of the bike, firmly anchored to the bottom bracket spindle. Standard aluminum BMX sprockets mount via a bolt to the crank arm. The ideal for park and street is a beefy construction with a low tooth count, typically 25 teeth, to maintain clearance when riding over obstacles.

A term for a static, balancing trick. The rider doesn't slide as in a grind, but rather jumps up, places their pegs (or pedals/tires) on the edge of the ramp, holds the balance for a few seconds to "stall" the position, and then elegantly drops back in.

The height of the frame measured from the center of the bottom bracket to the center line of the top tube junction. A low standover (around 7.5" to 8") creates a "sloping" look where the top tube drops down sharply, leaving riders plenty of room over the bike (ideal for throwing legs over during tailwhips). A tall standover (9.0" and up) provides the rider stability between the knees, a smoother ride, and a return to the traditional diamond (closed frame) shape.

A solid block of CNC or forged aluminum placed on the fork steerer. The handlebars are clamped firmly into it. The length (called reach, usually around 50 mm) and whether the bars are clamped from above (Top Load) or the front (Front Load), determines the final hand position for your ride.

View Stems

A specially shaped dirt riding arena in the woods consisting of a cascade of large jumps. The dirt style emphasizes rhythm, high trajectories, and huge stretched-out tricks without unnecessary spinning. Trail bikes tend to have longer, stability-enhancing frames and tires with more aggressive tread so they don't slip on the dirt.

The length of the top tube (in inches) is the most important guide to finding the right size for your BMX. The distance is measured from the center of the head tube to the center of the seat tube. For a junior around 150 cm tall, a shorter frame up to 20.0" is ideal. A standard adult height over 170 cm corresponds to mid-length frames (20.5" or 20.75"). For taller riders 180 cm and up, look for roomy models starting at 21.0" so knees don't hit the stem while moving.

The absolute number one braking system developed for Freestyle BMX. The two arms holding the brake pads are pulled together by cables (like a pair of pliers) and are mounted to the frame from the top. This protects the entire brake system, which doesn't stick out to the sides as much, so you won't easily kick it with your heel during tricks (unlike V-Brakes on mountain bikes).

A movement defying classic gravity. It is a riding element (and often the obstacle itself is named this way) where the BMX biker flies from a flat surface or launch ramp at high speed into a completely vertical or angled wall, "riding" the bike on the wall like a floor for a brief moment. After a few meters, they safely pop off back onto the ground or a connecting obstacle.

Indicates the number of teeth (T = Tooth) on the rear hub driver. In modern Freestyle BMX, 9 teeth is the absolute standard. Combined with a 25T sprocket, it offers the ideal gear ratio for both acceleration and top speed.

Indicates the number of teeth on a smaller screw-on freewheel. This type of freewheel with a smaller internal thread is designed for specific older hubs (so-called flip-flop hubs). It is rarely used on pro bikes today.

The number of teeth on a classic, large screw-on freewheel with a coarse thread. This system is now outdated, very heavy, and prone to breaking. At Katmar.cz, we do not recommend buying new bikes equipped with this type of freewheel for demanding Freestyle riding.

The most common size for the front sprocket. A 25-tooth sprocket is small enough that it doesn't get in the way during tricks or when dropping into ramps, and it's perfectly tuned for a 9T rear driver.

The numerical designation of the wheel and tire diameter in inches. The full-size adult standard for freestyle bikes is twenty inches (20"). The market also offers smaller and more maneuverable 16" and 18" versions, which respect the physiology of children and junior riders.

Indicates the crank construction. Three-piece (3-pc) and the newer, sleek two-piece (2-pc) cranks are essential designs consisting of a solid spindle fitted into crank arms on both sides. The opposite is the prehistoric one-piece (1-pc) crank, where a single bent piece of steel forms both pedal arms and the bottom bracket spindle. These have no place in Freestyle BMX and bend or break easily.

An old-school street design that has made a huge comeback. The handlebars aren't just bent and welded from two tubes (standard 2-pc), but are visually more angular, welded from four separate steel pieces. They offer a specific look, while their strength is fully comparable to classic 2-pc bars.

An important detail when buying new pedals. The larger 9/16-inch thread is used exclusively for threading into durable pro cranks (2-pc and 3-pc). The smaller 1/2-inch thread is used only for basic screw-on pedals on entry-level one-piece (1-pc) cranks.

The "H" stands for Holes, indicating the number of holes/spokes in one wheel (in the rim and hub). Almost all 20" Freestyle BMX wheels use a heavy-duty, reliable pressure distribution for hard impacts, consisting of exactly 36 steel spokes.