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How to Build a BMX Bike - A Comprehensive Guide
This guide covers BMX construction and upkeep. Assembling the various components on a BMX bike involves a certain learning curve. Every part of a BMX must be correctly attached as a flawed assembly not only reduces component longevity but also poses safety risks.
If you're a youngster just starting out in the sport, we suggest constructing your bike under the supervision of an adult or a seasoned rider. Do not hesitate to seek assistance from a local bike mechanic if a task becomes particularly challenging.
Overview
Constructing Your BMX Bike
In our video about BMX bike assembly, Marcus and Lasse demonstrate how to assemble a BMX bike from the ground up. Watch it to get motivated before you begin assembling your own BMX, or to understand the sequence for fitting the different parts.
The video provided offers a basic run-through of BMX bike assembly. Additional down in this handbook are more comprehensive instructions on fitting some of the vital BMX components.
SkatePro’s Recommendations for BMX Assembly
Follow these guidelines when building your BMX:
- Young riders should assemble a BMX only with adult or experienced guidance.
- Use the proper tools for their specific purposes to prevent part damage and to ensure appropriate installation.
- Before riding, tighten all nuts and bolts on your new bike.
- Take your time and proceed with patience - for your safety and the lifespan of your parts.
BMX Components - Understanding BMX Structure
A complete BMX bike consists of the following components:
- Frame
- Bar
- Grips
- Stem
- Headset
- Headset Spacer
- Fork
- Wheels
- Rims (Rim strips)
- Tyres (Tubes)
- Spokes w/ Nipples
- Front Hub
- Pedals
- Cranks
- Sprocket
- Bottom Bracket
- Chain
- Rear Hub
- Driver / Freewheel
- Seat
- Seat Post
In this handbook, you'll encounter tutorial videos on how to fit several of these components.
Which Tools Are Necessary for BMX?
Fitting and maintaining a BMX bike requires only a few crucial tools. A standard BMX tool kit usually contains everything needed to build a partially assembled complete BMX fresh from the box. Carrying a BMX tool kit during rides is always advisable to avoid cutting short a great session due to a loose part.
We suggest having these tools on hand when assembling, maintaining, or repairing your BMX:
- Hex keys/Allen wrenches: 4, 5, 6 & 8 mm
- Wrench sockets: 15, 17, 19 mm (deep socket for pegs)
- Open-ended 15 mm wrench for pedals
- Chain breaker
- Tire levers
- Spoke wrench
- Air pump
- Grease/lubricant for screws
- Tire levers
- Adjustable wrench
- Brake cable wire cutter
- Bottom bracket installation tool or a soft-headed hammer
Over time, additional tools will be needed for proper maintenance and disassembly of parts. You'll likely wish to grow your tool collection as the necessity for more specialised tools becomes evident.
At SkatePro, we maintain a range of BMX Tools for basic upkeep and assembly:
Step-by-Step BMX Bike Assembly
Employing an experienced mechanic to assemble your BMX may not always be feasible. By following the tutorial videos below, you should have a good beginning point, but if it becomes too challenging, we recommend seeking assistance from someone experienced with bikes. To make things even easier for you, we have listed each video sequentially, offering step-by-step guidance for constructing a complete BMX bike from scratch.
Fitting the BMX Crankset
In the video provided, we demonstrate how to fit a three-piece crankset. The three-piece design is the most prevalent type, and the process for a two-piece crankset is quite similar – the main distinction being that one crank is pre-attached to the spindle in two-piece models.
It's crucial to match the spindle's diameter with the internal diameter of your bottom bracket bearings for compatibility. Your bottom bracket bearings' internal diameter is typically 19 mm, 22 mm, or 24 mm, with 19 mm being the most common spindle size.
If a new crankset is needed, you can explore our offerings:
Fitting a BMX Bolt-On Sprocket
The procedure for fitting a BMX sprocket is quite straightforward. The most frequently used type for freestyle BMX sprockets is attached via bolts that secure to the sprocket and interlink with the crank arm. Just align the bolt-hole on the sprocket with the corresponding ones on the crank, and secure it.
If the diameter of the spindle hole is larger than the crank spindle, a spacer is required.
Applying BMX Rim Tape
Installing rim tape is an essential step before fitting tires and tubes. While it is generally straightforward, ensuring the valve hole in the rim tape correctly aligns with the valve hole in the rim is crucial.
Explore BMX rim tape options here:
Installing BMX Tyres and Tubes
Begin by positioning one-half of the tyre onto the rim, keeping the other half free. Slightly inflating the tube before installation prevents it from pinching or twisting against the tyre and rim, always confirming the valve sits correctly before fully securing the tyre.
Note: When installing the tyre on the rear wheel, ensure you observe the directional pattern of the tyre.
Fitting the Front BMX Wheel
Slide the front wheel into the fork, gently tightening it by hand. Make sure it's thoroughly aligned before further securing the wheel from both sides. Observe the tyre pattern direction, and simply rotate the wheel if it's reversed.
Installing the Rear BMX Wheel
Before attaching the rear wheel, disengage the chain from the front sprocket, providing enough slack to secure it onto the rear wheel sprocket. Position the wheel, reattach the chain to the front sprocket, and adjust until the chain is neither excessively loose nor overly tight. Finally, securely fasten the bolts on both sides using a wrench.
- BMX chain tension: Aim for a slight movement where the chain can be lifted slightly by touch, but not exceeding half an inch.
Installing a BMX Chain
Installing a new BMX chain requires precise shortening to fit your setup. To shorten a chain, you will need a bike chain breaker, which can be found here:
The video below shows you how to properly install a half-link chain:
Fitting BMX Pedals
When installing BMX pedals, two things are important:
- Correctly identify the left and right pedals before fitting them accurately on either side.
- Apply grease to the screws for optimal tightness and to ease future removal.
The following video provides step-by-step instructions for fitting BMX pedals:
BMX Headset Installation
It is always recommended to use grease during the fitting of an integrated headset, specifically on the bearing cups. Make sure the bearings are aligned correctly in the cups, and don't forget the C-ring installation.
Fitting a BMX Fork
Fitting the BMX fork is usually a straightforward process. The C-ring is an often overlooked element, but key to ensure a snug fit.
Installing the BMX Stem
It's crucial to apply grease when fitting the compression bolt and stem bolts to ensure a secure fit and make future removal easier.
During the stem fitting, check there's a gap between the steerer tube top and the stem top to allow compression. If the steerer tube extends beyond or aligns precisely with the stem's top, a spacer is needed.
Post-tightening the compression bolt, ensure the stem properly aligns with the fork before fastening the side bolts, thereby securing the stem to the fork.
Attaching the BMX Handlebars
Once you have unscrewed the four stem bolts, you can attach the handlebars. Ensure the knurled centre section of the handlebar sits in the middle of the stem. Gradually tighten the bolts in a crisscross pattern to ensure even tightening across the stem.
If you are looking to upgrade or replace your handlebars, discover our BMX Bar selection:
Fitting BMX Grips
Spraying alcohol-based window cleaner on the handlebars simplifies sliding the grips onto the handlebars. The alcohol helps the cleaner evaporate, ensuring the grips stick solidly to the handlebars without slipping.
Installing BMX Bar Ends
Typically, plastic bar ends are gently hammered into handlebars using a rubber mallet, whereas metal bar ends are fastened securely with an Allen key.
Fitting a BMX Pivotal Seat and Seat Post
Pivotal seats are fitted to the seat post via a hole on top of the seat. It's essential to ensure seat and seat post compatibility for proper fitting and operation.
All your BMX seating needs can be found here:
