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Constructing a BMX Bike - An Extensive Manual
This serves as our manual for BMX construction and upkeep. Assembling the various components of a BMX bike presents a learning challenge. Properly mounting every part is vital, as any incorrect assembly can reduce component longevity and pose safety risks.
If you’re a young enthusiast just entering the sport, we advise assembling your bike with the guidance of an adult or seasoned rider. Bear in mind that a local bike mechanic could assist if you find anything particularly challenging.
Overview
Constructing Your Personal BMX Bike
Check out our BMX bike build video, where Marcus and Lasse have a great time guiding you through assembling a BMX bike from the ground up. Watch the video to get motivated before building your own BMX, or to understand the correct sequence for mounting the different BMX components.
The video above provides a brief and basic BMX bike assembly. Later in this guide, we offer comprehensive instructions on how to install some of the key BMX components.
SkatePro’s Guidelines for Assembling BMX Bikes
Always adhere to these suggestions when assembling your new BMX:
- Youngsters should assemble a BMX only under the supervision of an adult or a seasoned rider.
- Use the correct tools for each task to prevent damage and to ensure correct placement.
- Ensure all nuts and bolts are fully tightened before taking your new bike for a spin.
- Exercise patience and dedicate sufficient time to do everything correctly—for your safety and for the parts’ lifespan.
BMX Bike Components - Understanding BMX Structure
A complete BMX bike consists of the following elements:
- Frame
- Bar
- Grips
- Stem
- Headset
- Headset Spacer
- Fork
- Wheels
- Rims (Rim strips)
- Tyres (Tubes)
- Spokes with Nipples
- Front Hub
- Pedals
- Cranks
- Sprocket
- Bottom Bracket
- Chain
- Rear Hub
- Driver / Freewheel
- Seat
- Seat Post
Further down in this guide, you will find instructional videos on fitting many of these components.
Essential Tools for BMX Assembly
Only a minimal range of essential tools is necessary to assemble and maintain a BMX. A typical BMX tool kit usually contains everything required for assembling a partly-assembled complete BMX bike straight from the box. Bringing a BMX tool kit with you when riding is advisable, so you won’t need to cut an amazing session short due to a loose component.
For bike assembly, maintenance, or repairs, we suggest keeping these tools on hand:
- Hex keys/Allen wrenches: 4, 5, 6 & 8 mm
- Wrench sockets: 15, 17, 19 mm (deep socket for pegs)
- 15 mm open-ended wrench for pedals
- Chain breaker
- Tyre levers
- Spoke wrench
- Air pump
- Grease / lubricant for threads
- Tyre levers
- Adjustable wrench
- Brake cable wire cutter
- Bottom bracket installation tool or hammer with a soft head
Eventually, you’ll require more tools for proper maintenance and disassembly. You may want to expand your bike tools collection as more specialised tools become necessary.
At SkatePro, we always have a range of BMX Tools available for basic maintenance and setup:
Step-by-Step Guide to BMX Bike Assembly
Getting an experienced bike mechanic to assemble your BMX isn't always an option. If you follow the instructional videos below, you'll have a sound starting point, but if it proves too difficult, we suggest seeking help from someone with bike expertise. To simplify the process, we’ve listed all the videos in sequence, providing detailed steps to build a complete BMX bike from scratch.
Installing the BMX Crankset
The video below details how to fit a three-piece crankset. While three-piece cranksets are most commonplace, installing two-piece cranksets is similar—the crucial difference being that, in two-piece cranksets, one crank is already attached to the spindle.
Regarding compatibility, ensure the spindle diameter matches the inner diameter of your bottom bracket bearings, which could be 19 mm, 22 mm, or 24 mm. Typically, the spindle size is 19 mm.
If you need a new crankset, you can explore our range:
BMX Bolt-On Sprocket Installation
Fitting a BMX sprocket is relatively easy. The most common freestyle BMX sprockets are installed via bolts that connect the sprocket to the crank arm. Align the bolt-hole on the sprocket with the crank threads, then secure it.
If the spindle hole in your sprocket is larger than the crank spindle, using a spacer is needed.
Installing BMX Rim Tape
Before adding tyres and tubes, ensure to fit rim tape. Though there’s not much that can go wrong, make sure to align the tape’s hole with the rim’s valve hole.
Shop for BMX rim tape:
Installing BMX Tyres and Tubes
Start by mounting half the tyre on the rim, leaving the rest free. Slightly inflate the tube before installation to avert pinching or twisting between the tyre and rim, and ensure the valve is straight before fully attaching the tyre.
Note: Take note of the tyre pattern direction when mounting the tyre on the rear wheel.
Installing the BMX Front Wheel
To mount the front wheel, slip it into the fork and gently tighten with your fingers. Ensure perfect alignment before securely fastening the wheel from each side, paying attention to the tyre pattern’s direction. Flip the wheel if fitted backwards.
Installing the BMX Rear Wheel
Before attaching the rear wheel, free the chain from the front sprocket for adequate slack and fit it onto the rear wheel sprocket. Slide the wheel into position and reattach the chain onto the front sprocket. Adjust the wheel to ensure neither too loose nor overly taut chain tension. Use your wrench to tighten the bolts thoroughly on both sides.
- Chain tension in a BMX: Aim for a slight upward play when the chain is moved, but not exceeding half an inch.
Installing the BMX Chain
Installing a new BMX chain involves cutting your chain to the exact length for your setup. You’ll require a bike chain breaker, available here:
In the video below, learn to correctly install a half-link chain:
Installing the BMX Pedals
Two key aspects while fitting BMX pedals:
- Ensure you have identified the left and right pedals correctly and mount them accordingly.
- Add grease to the threads for proper tightness and facilitate future removal.
The video illustrates how to mount your BMX pedals:
Installing the BMX Headset
When fitting an integrated headset, apply grease to the bearing cups. Ensure bearings sit correctly within cups and remember to fit the C-ring.
Installing the BMX Fork
Fork installation is simple. Just remember to include the C-ring for a secure fit.
Installing the BMX Stem
When it comes to installing compression and stem bolts, ensure to grease them for a tight fit and easy future removal.
During stem installation, keep a gap between the steerer tube top and the stem’s top for compression room. If the tube is beyond or exactly at the top of the stem, a spacer is necessary.
After the compression bolt is tightened, verify the stem aligns with the fork before securing the side bolts for proper stem to fork attachment.
Installing the BMX Handlebar
Once the four stem bolts are unscrewed, you can install the handlebars. Ensure the knurled centre of the handlebar is centred with the stem mount. Tighten bolts gradually in a cross pattern for equal tension across the stem.
Browse our selection of BMX Bars if you’re considering an upgrade or replacement:
Installing the BMX Grips
Use alcohol-based window cleaner spray to make sliding grips onto the handlebars easier. The alcohol substance helps the cleaner evaporate, enabling firm grip adherence without sliding off.
Installing the BMX Bar Ends
Plastic bar ends get tapped into handlebars using a rubber mallet while metal ones are securely fastened using an Allen key.
Installing the BMX Pivotal Seat and Seat Post
Pivotal seats attach to the seat post through an opening at the top. Ensuring seat and post compatibility is essential for correct fit and functionality.
Find everything required for an ideal BMX seating experience here:
