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Crafting a BMX Bicycle: A Complete Guide
We present our manual for assembling and maintaining BMX bicycles. Assembling various components on a BMX bike involves a learning process. Ensuring each part is precisely mounted is essential, as incorrect assembly not only reduces the lifespan of the components but also poses potential safety risks.
If you're a young enthusiast new to BMX biking, we suggest constructing your bike under adult supervision or with the guidance of an experienced cyclist. Should any task prove too challenging, reaching out to a local bike mechanic is advisable.
Overview
Constructing Your BMX Bicycle
In our video showcasing a BMX bike assembly, Marcus and Lasse have fun while demonstrating how to build a BMX from the ground up. Watch it to get inspired before working on your own BMX, or to learn the sequence in which the different parts should be assembled.
The video above offers a quick introduction to BMX bike assembly. Further within this guide, we provide comprehensive instructions on installing some crucial BMX components.
SkatePro’s Recommendations for Assembling BMX Bicycles
Ensure you adhere to the following suggestions when constructing your BMX:
- Children should not put together a BMX without adult supervision or the help of an experienced rider.
- Employ the correct tools for each task to avoid damaging parts and to ensure proper assembly.
- Tighten all nuts and bolts before taking your new bike for a ride.
- Be patient and thorough - for both your safety and the durability of your components.
Understanding BMX Bicycle Components
A comprehensive BMX bike consists of the following components:
- 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
Below in the guide, you will find instructional videos on assembling many of these parts.
Essential Tools for BMX Assembly
Only a handful of vital tools are necessary to both assemble and maintain a BMX bike. A typical BMX tool kit is equipped to help you put together a partially assembled complete BMX bike straight out of its packaging. Bringing a BMX tool kit while riding is always a good idea, ensuring a loose part won't prematurely end an awesome session.
We recommend having these tools readily available when building, servicing, 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
- Tyre levers
- Spoke wrench
- Air pump
- Grease / lubricant for threads
- Tyre levers
- Adjustable wrench
- Brake cable wire cutter
- Bottom bracket installation tool or a hammer with a soft head
Over time, you'll require more tools for the optimal maintenance and disassembly of parts. Your collection of bike tools is likely to expand as the need for more specific tools grows.
At SkatePro, we consistently stock a range of BMX Tools for basic upkeep and assembly:
Step-by-Step BMX Assembly Instructions
Sometimes, enlisting a professional bike mechanic to build your BMX isn't feasible. The instructional videos below will help get you started, but if any step seems too complex, seeking help from someone experienced with bikes is recommended. We've curated these videos sequentially, offering step-by-step guidance to assembling a full BMX bike from scratch.
Installing the BMX Crankset
The following video demonstrates how to install a three-piece crankset, the most common type. Two-piece cranksets follow a similar installation process, but one crank is already attached to the spindle.
Compatibility is crucial; ensure the spindle diameter matches the bottom bracket bearings' inner diameter. The inner diameter is typically either 19 mm, 22 mm, or 24 mm, with 19 mm being the most common size.
If a new crankset is needed, browse through our offerings:
Attachment of BMX Bolt-On Sprocket
Fitting a BMX sprocket is relatively simple. The most prevalent style of freestyle BMX sprockets secures via bolts that affix to the sprocket and connect with the crank arm's threading. Properly align the sprocket bolt-hole with the crank's threads and screw it in place.
If the hole in the spindle is larger than the crank spindle, a spacer will be necessary.
Installing BMX Rim Tape
Before assembling tyres and tubes, remember to apply rim tape. Though it's straightforward, ensure the rim tape hole aligns with the rim hole where the valve will go through.
Find BMX rim tape here:
Fitting BMX Tyres and Tubes
Initially, mount half of the tyre onto the rim while leaving the other half free. Slightly inflate the tube prior to installation to prevent twisting or pinching between the tyre and the rim, and ensure the valve sits straight before fully mounting the tyre.
Note: When fitting the tyre on the rear wheel, be mindful of the tyre pattern's direction.
Installing the BMX Front Wheel
While attaching the front wheel, slide it into the fork and gently tighten it with your fingers. Make sure it is perfectly aligned before tightening the wheel from both sides. Pay attention to the tyre pattern's direction; flip the wheel if it's backward.
Fitting the BMX Rear Wheel
Before attaching the rear wheel, release the chain from the front sprocket to create enough slack to fit it on the rear wheel sprocket. Slide the wheel into position and reattach the chain to the front sprocket. Adjust the wheel position to ensure the chain is neither too taut nor too slack. Finally, use your wrench to secure the bolts tightly on both sides.
- BMX chain tightness: Aim for a slight amount of movement where the chain can shift up when touched, but not exceeding half an inch.
BMX Chain Fitting
Fitting a new BMX chain requires shortening it to perfectly fit your setup. To do this, you need a bike chain breaker, which is available here:
The following video demonstrates how to correctly install a half-link chain:
Fitting BMX Pedals
When attaching BMX pedals, two key points should be observed:
- Correctly identify the left and right pedals and fit them on the appropriate side.
- Add grease to the threads to ensure secure fastening and easy removal in the future.
Watch the video below to learn the correct way to install BMX pedals:
Fitting the BMX Headset
For an integrated headset, apply grease to the bearing cups. It's crucial to properly orient the bearings within the cups, and don't overlook installing the C-ring.
BMX Fork Fitting
Attaching the BMX fork is straightforward. The main thing to remember is not to forget the C-ring, ensuring a secure fit.
BMX Stem Fitting
Greasing the compression and stem bolts aids a snug fit and facilitates easier removal later on.
During the stem fitting, ensure there is a slight gap between the top of the steerer tube and the stem top to allow for compression. If the steerer tube protrudes above or is flush with the stem top, a spacer is necessary.
After the compression bolt is tightened, ensure the stem aligns with the fork before securing the side bolts, clamping the stem to the fork effectively.
Fitting BMX Handlebars
Once the four stem bolts are loosened, you're ready to mount the handlebars. It's crucial to ensure the knurled centre of the handlebar aligns centrally within the stem. Gradually tighten the bolts in a cross pattern to ensure even tightening across the stem.
Explore our BMX Bar selection for upgrades or replacements:
Attaching BMX Grips
Using an alcohol-based window cleaner on the handlebars aids in easily sliding the grips into place. The alcohol evaporates, helping the grips stick firmly to the handlebars without slipping.
Installing BMX Bar Ends
Plastic bar ends are typically inserted into the handlebars with a rubber mallet, while metal bar ends require an Allen key for secure screwing.
Setting Up BMX Pivotal Seat and Seat Post
Pivotal seats are attached to the seat post through a top hole in the seat. It's essential to ensure seat and seat post compatibility for proper fitting and function.
Find everything needed for optimal BMX seating here:
