How to Build a BMX Bike

Building a BMX bike from parts is one of the best ways to end up with a bike that fits the way you ride. It is also easy to get wrong if you pick parts in the wrong order. This guide walks through a sensible order, and you can follow along in the BMX Creator builder as you go.

1. Start with the frame

The frame decides almost everything else. Look at the top tube length first. Taller or bigger riders usually want a longer top tube, and many riders choose between roughly 20 and 21 inches. Then check the frame’s details: the head tube style (integrated, mid, or external headset), the bottom bracket shell, the rear dropout size, and whether it has brake mounts if you want brakes.

2. Choose the fork

The fork has to match your wheel size and your front axle. Most 20 inch forks use a 10mm or 14mm axle, and some older or race forks use 3/8 inch. Check whether the steerer tube is standard or tapered, because that changes which headset you need.

3. Pick the headset, stem and bars

The headset connects the fork to the frame and has to match both. The stem clamps the bars and the fork, and bars come in different rises, with 8 to 9.5 inches being very common. Grips finish the front end. If you want brakes, plan the lever and cable now.

4. Build the drivetrain

The drivetrain is where most compatibility mistakes happen. Pick cranks first and note the spindle size, because the bottom bracket and the sprocket must match it. Then pick the sprocket, the chain, and the rear hub and driver or cog. Pedals thread into the crank arms, so check the thread size too.

5. Wheels and tires

Choose a rim, hubs and tires that all match your wheel size. For a 20 inch BMX build you want 20 inch rims and tires. Check that the tires fit your frame and fork clearance, and that your rear hub matches your frame’s dropouts.

6. Seat and seat post

Pivotal seats clamp onto pivotal posts, while railed seats use a railed post or clamp. They are not interchangeable, so match the pair, then confirm the post diameter fits your frame’s seat tube.

7. Brakes, or no brakes

Many street and park riders run brakeless. If you want brakes you need a brake caliper, a lever, a cable, and brake mounts on the frame. A detangler (often called a gyro) lets you spin the bars without tangling the cable.

Before you order

BMX Creator is a fun tool, and some parts you pick may not be compatible with each other. Check the shop’s own listing, and please consult a bike mechanic before ordering anything. Ready to try it? Head back to the builder on the home page.