Seat and Seatpost

A BMX seat and seatpost together make up the saddle assembly. The post slides into the frame's seat tube and clamps there, and the seat sits on top. On freestyle bikes the seat is small, and street riders often run it very low.

What it does

The seat gives a place to sit during climbs, sprints or rest. It also affects pedalling height and body position. On a trick bike it often does little work, so the aim is to keep it out of the way.

Types and standards

Type	Description	Typical use
Pivotal	The seat tab locks into a post head with a bolt that sets the tilt	The most common freestyle setup. Compact and strong.
Tripod	The seat mounts to the post on three points	Similar use to pivotal. Strong and neat.
Combo	The seat and post form one moulded unit	Light, simple and cheap. Height fixed or limited.
Railed	A conventional seat on metal rails, clamped to the post	Adjustable fore and aft. Common on race and older bikes.

Seat heights

• Slammed (or low). The seat sits right down on the seat tube or the post is cut short. Common in street and park.
• Mid. A little height for a mix of pedalling and tricks.
• Full height. Common on race bikes and for longer rides.

Seatpost

The standard BMX post diameter is 25.4 mm (1 inch). It must match the inside of the seat tube. Posts are often cut to the desired length. Most are steel or aluminium. A seat clamp on the outside of the frame tube locks the post in place.

Sizing and compatibility

• Post diameter. Check the frame's seat tube inside diameter: 25.4 mm is standard.
• Seat clamp. Match the clamp to the frame's seat tube outside diameter. Many bikes include a clamp with the frame.
• Seat mount type. The post and seat must match. A pivotal seat needs a pivotal post. A railed seat needs a post with a rail clamp.
• Height. Set the seat so you can pedal comfortably if you need to. Most trick riders accept a low height.
• Seat tube angle and length. These are part of frame geometry. They affect how the seat sits relative to the cranks.

How to choose

1. Decide how much you pedal. Race and dirt riders pedal more, and need more height. Street riders pedal less.
2. Pick the seat type: pivotal or tripod for simplicity, railed if you want fore and aft adjustment.
3. Check the post diameter against your frame.
4. Think about weight. Combo seats are light, but they cannot be adjusted much.
5. Look at the finish. A good seat resists tears and damage.

Basic seats cost little, and stronger or lighter versions cost somewhat more. Check the build rather than the label.

Why street riders slam the seat

On street spots the seat can catch on ledges, rails and the rider's own legs. Slamming it avoids snags and lets the rider move freely. Some riders choose to remove the seat entirely. Others keep it for rest or for a casual ride between spots. Race bikes need the opposite: a higher seat to allow full pedal power.

Maintenance

• Bolt check. Tighten the seat clamp and pivot bolts regularly. A loose seat can shift mid-trick.
• Grease. Put a little grease on the post before inserting it. This stops it seizing in the frame, especially on steel frames.
• Inspect the post. Look for cracks at the clamp area and at the base of the seat mount.
• Seat cover. If the cover tears, water gets in the foam. Replace the seat when it starts to fall apart.
• Cut posts carefully. Mark the length twice, cut square and deburr the end.

Related parts

• Frame geometry: seat tube length and angle.
• Pedals: seat height changes pedalling reach.
• Street: where slammed seats are most common.
• Racing: where full height seats are standard.
• How to set up a new BMX: includes seat position.