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A Complete Guide to Assembling a BMX Bike
This serves as our manual for constructing and maintaining BMX bikes. Learning to attach various components to a BMX can be somewhat challenging. Proper assembly is imperative, as incorrect mounting can shorten the lifespan of your parts and pose safety risks.
If you are a young beginner in this sport, we advise assembling your bike with the oversight of an adult or an experienced rider. Additionally, a local bike mechanic can assist if any task is too challenging.
Overview
Steps to Construct Your BMX Bike
In our video on building a BMX bike, Marcus and Lasse demonstrate how to construct a BMX from start to finish. Watch this to get inspired before you start assembling your own BMX, or to learn the sequence for installing the various BMX components.
The video above offers a brisk and basic walkthrough of BMX assembly. Later in this guide, you will find more detailed instructions on fitting some crucial BMX parts.
SkatePro’s Tips for Assembling BMX Bikes
When putting together your BMX, adhere to these guidelines:
- Children should always have an adult or seasoned rider on hand for guidance when assembling a BMX.
- Select the right tools for each specific task to avoid damage and ensure components are properly installed.
- Ensure every nut and bolt is tightly secured before riding your new bike.
- Exercise patience and thoroughness for safety and to extend the lifespan of your components.
The Composition of BMX Bikes
A complete BMX bike comprises the following parts:
- 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
Further along in this guide, there are instructional videos on installing many of these parts.
What Tools are Necessary for BMX Assembly?
To both assemble and maintain a BMX bike, a few essential tools are required. Usually, a standard BMX toolkit includes the necessary tools for assembling a partly pre-assembled complete BMX just out of the box. Carrying a BMX tool kit during rides is always advisable, enabling you to address any loose parts without cutting a great session short.
When assembling, maintaining, or repairing your BMX, we suggest having these tools available:
- 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 threads
- Tire levers
- Adjustable wrench
- Brake cable wire cutter
- Bottom bracket installation tool or a hammer with soft head
Long-term, more tools will be needed for effective upkeep and part disassembly. As the need for more specific tools arises, you'll likely wish to augment your collection of bicycle tools.
We always have a range of BMX Tools available for basic assembly and maintenance at SkatePro:
A Step-by-Step Guide to Assembling a BMX Bike
Getting a bike mechanic experienced with BMX assembly isn't always a feasible choice. If you follow the instructional videos below, you should have a good base, but should it be too complicated, seek help from someone with bike experience. All these videos are listed sequentially, supplying you with detailed instructions for constructing a complete BMX bike from scratch.
Installing a BMX Crankset
In the following video, we demonstrate how to install a three-piece crankset. This type of crankset is the most prevalent, and the installation of a two-piece one follows a similar process – the key difference being that one crank of the two-piece set comes pre-attached to the spindle.
It is essential to match the spindle diameter with the inner diameter of your bottom bracket bearings for compatibility. The inner diameter typically measures either 19 mm, 22 mm, or 24 mm, with 19 mm being the prevalent spindle size.
If in need of a new crankset, check our collection:
Attaching the BMX Bolt-On Sprocket
Mouting a BMX sprocket is generally straightforward. The common freestyle BMX sprockets utilise bolts that lock into the crank arm. Align the bolt-hole in the sprocket with the crank threads and proceed with installation.
If the spindle hole's diameter is larger than the crank spindle, a spacer must be used.
Installing BMX Rim Tape
Always fit the rim tape before adding tyres and tubes. While the process is relatively straightforward, one thing to remember is to align the hole in the rim tape with the hole in the rim where the valve will pass through.
Find BMX rim tapes here:
Installing BMX Tyres and Tubes
Start by fitting one side of the tyre onto the rim, leaving the other free. Slightly inflate the tube before inserting to avoid twists or pinching between the tyre and rim. Also, make sure the valve is straight before completing the tyre fitting.
Note: When mounting the rear tyre, note the tread direction.
Fitting the BMX Front Wheel
To properly install the front wheel, slide it into the fork and hand-tighten it. Ensure it is aligned correctly before tightening from both sides. Check the tyre tread direction and flip the wheel if it is incorrect.
Securing the BMX Rear Wheel
Before installing the rear wheel, detach the chain from the front sprocket to provide sufficient slack for installation on the rear sprocket. Secure the wheel, ensuring the chain has the right tension, neither too tight nor too loose. Lastly, utilise a wrench to secure the bolts firmly on both sides.
- BMX chain tension: Allow for a slight slack, enough for half an inch of movement upwards when nudged.
Fitting the BMX Chain
Installing a new BMX chain involves shortening it to suit your setup precisely. To adjust the chain length, a bike chain breaker tool, provided here, is required:
The following video will guide you through proper installation of a half-link chain:
Installing BMX Pedals
When attaching BMX pedals, bear in mind two important factors:
- Ensure you have identified the left and right pedals and mount them on the appropriate sides.
- Grease the threads to guarantee proper tightening and facilitate future disassembly.
Here's a video demonstrating the precise installation of BMX pedals:
Installing the BMX Headset
For an integrated headset installation, it is advisable to apply grease on the bearing cups. Make sure the orientation of the bearings in the cups is correct and remember to fit the C-ring.
Fitting the BMX Fork
The BMX fork installation process is straightforward. A common error is forgetting the C-ring, so ensure its inclusion for a seamless fit.
Installing the BMX Stem
While fitting the compression bolt and stem bolts, apply grease to ensure a secure fit and to simplify future removal.
During stem installation, there should be a gap between the top of the steerer tube and the top of the stem to allow for compression. If the steerer tube extends beyond or is level with the stem top, a spacer is needed.
After tightening the compression bolt, confirm alignment of the stem with the fork before securing the side bolts to fix the stem in place.
Fitting BMX Handlebars
Once the four bolts on the stem are unscrewed, you can mount the handlebars. The knurled middle part of the handlebar must be perfectly centred. Tighten the bolts in a criss-cross pattern to ensure even tightening.
If you're considering an upgrade or replacement, explore our selection of BMX Bars:
Fitting BMX Grips
Spraying the handlebars with alcohol-based window cleaner eases the installation of grips. The alcohol allows the cleaner to evaporate, ensuring the grips adhere to the handlebars without slipping.
Installing BMX Bar Ends
Typically, plastic bar ends are inserted into the handlebars with a rubber mallet, whereas metal bar ends are fastened using an Allen key.
Fitting BMX Pivotal Seat and Seat Post
Pivotal seats are mounted on the seat post via a hole on top of the seat. Verifying compatibility between seats and seat posts is vital for accurate fitting and functionality.
Find everything necessary for an optimal BMX seating setup here:
