How to Buy Replacement Parts for a BMX Bike

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How to Buy Replacement Parts for a BMX Bike

BMX stands for Bicycle Motocross. It began as a grassroots craze around improvised tracks with bumps and berms (raised corners) in the 1970’s, faded in popularity with the advent of mountain bikes, and has stormed back to Olympic sports status.

A Bike to Suit the Discipline

The development of BMX has resulted in two disciplines, Track Racing and Freestyle.  Within Freestyle there are four disciplines – Street, Flatland, Dirt Jumping and Ramp and Park. A quality, standard BMX bike with a single gear and 20 inch wheels is versatile enough for a beginner to have fun and maybe attempt the different styles. Those who want to go on to specialise in a particular branch of BMX should note that each discipline has its own variations in the specification of the bike and components.

Track Racing Race bikes are much longer than other BMX's to keep them more stable at high speeds and are lighter to help the rider get faster acceleration. They are usually fitted with one brake (rear) and knobbly tyres.

Street This means finding everyday urban obstacles like kerbs and rails and doing tricks on or over them. This requires a bike that is light enough to perform but strong enough to withstand impact without breaking. 

Flatland This involves doing tricks on a flat piece of ground such as a car park. This requires short, light bikes that can be spun. They have four fat pegs to stand on and gyros to prevent brake cables from tangling.

Dirt Jumping or trail riding often taking place in the woods or over big improvised jumps, this style requires a bike that is heavier than a race bike, but lighter than a street bike.  

Ramp and Park This involves doing tricks and riding around specially designed circuits made of concrete or wood, often as part of skate parks. A street bike would be perfectly suitable.

BMX Bike Basics

Those who already have a BMX bike will probably simply replace parts like-for-like from the original manufacturer.  This guide is for people who want to choose parts which will enable them to modify or upgrade their bike to perform better in the above BMX disciplines.  Other people are perhaps thinking about custom building a complete BMX bike from selected parts to suit their preferences and ambitions.  

To make choosing parts easier, it is convenient to divide a BMX bike into seven separate, logical systems.















Most of these systems have essential sub-components and important accessories

BMX Bike Systems Explained 


Good frames tend to be made from chromoly - as opposed to the heavier and weaker high-tensile steel used in cheaper versions - and there is a general trend towards lighter and stronger frames with each season. Look for 4130 Cromoly or Cro-mo for more strength and less weight. Aluminium frames are largely in the racing bike category. The top tube length should be chosen for comfort. The most common size for complete bikes is 20.5.  This should suit people from 5ft to 6ft in height. Taller people or children should select correspondingly longer or shorter tubes.  When choosing for young people allow for growth.


The same principles for choosing frames also apply to forks.  For lightness and resistance to bending, Chromoly is the preference. There is a choice of 10 inch or 12 inch versions, sometimes tapered to save weight.  Forks should be drilled ready to accept pegs.

Pegs protect both bike and rider from scraping on the ground. Stunt pegs are made from steel for ultimate toughness, and titanium, aluminium, and even plastic for extra lightness. They come in 10mm and 14mm sizes and for front and rear wheels.


This is the set of components that allow the rider to drive the bike forwards. It is made up of; the crankset, bottom bracket, sprocket, pedals, chain and rear hub.  Although BMX bikes have no gears to change, the relationship between the sprocket (also known as chain wheel) and the rear hub freewheel determines how fast the rider needs to pedal in order to achieve a given speed.


The crank arm connects the pedal to the bottom bracket and has to be strong enough to withstand a lot of pressure. Look for tubular 3-piece options with splined spindles. These offer protection for the cranks wearing out or coming loose. Remember that cranksets may require a separate purchase of the bottom bracket.


  Selecting a bigger sprocket - up to 36 teeth - means it will be harder to pedal, while rings as small as 23 teeth can enable the setting up of a micro drive, saving weight and improving ground clearance. To get the right ratio, think about the size of the smaller cog which fits to the rear hub.


Alloy pedals last longer whilst plastic pedals are lighter. Varying levels of grip and profile thickness allow the feet to get just the right feel when pressing down.  Both kinds come in many colours. More expensive models typically have replaceable pins for longevity.


transfer pedal input to power at the back wheel. Street or flatland riders who want to tailor their drivetrain can choose coloured half link versions. Lightweight chains will suit trail or dirt jump riders.

Bottom Bracket (BB)

comes in several designs.  USA or American found on entry level bikes are the most common, being the largest and having unsealed bearings.  Mid BBs and Spanish BBs are smaller and in most cases use sealed bearings which last a lot longer.


A new set of wheels will change the ride characteristics of a bike. Fully built wheels are available individually for either the front or rear, or wheel sets can be bought comprising both. Wheels can also be individually built with rims, spokes and front and back hubs. Racing BMX bike wheels vary from 16 inch to 26 inch diameter with 20 inch being the most popular. The various freestyle BMX bike wheel sizes include 16 inch and 18 inch diameters for smaller riders with 20inch for most other riders. Tyres can be chosen separately.

Rims are the outside part of the wheel and come in standard single or double wall options, double being stronger and lasting longer.

Front hub  Look for sealed bearings for durability.  Unsealed bearings will be fine for newcomers while they are learning.

Rear hub There are two types. The regular or freewheel hub with anything from 13 to 16 teeth or the more reliable cassette type which use anything from 8 teeth upwards and are built into the hub itself. These are lighter in weight and give more clearance for grinding tricks. Traditionally more expensive, cassettes are becoming more affordable.

Spokes Most street and park bikes have 36 spokes but more competitive riders use 48 spokes for extra strength. Race bikes usually have 36 spokes. Wheels for children can be built with 18 or 28 spokes. 

Tyres Although usually wider on the front than the rear, some street bikes now feature equal sized tyres to give more grip and cushioning at the back. As BMX bikes become lighter, while retaining their toughness, there is a trend to bring folding tyre options to the sport.



Almost always referred to as bars, these should be chosen with the same material as the frame and forks.  Also look out for heads treated and/or multi-butted tubing for better weight to strength ratio.  If possible try different widths and heights as this can make a big difference to the ride.


Having the right pair of bar grips - with the right level of comfort and girth - can vastly improve the feel of the bike, while bar ends protect from any potential sharp edges at the side of the handlebars.


clamp the bar in place on the forks and are available in a variety of textures and colours to provide individuality. All stems are comparable in strength.


contain the bearings that allow handlebars to be turned for smooth steering. There are two kinds. Threadless (sometimes called A-head) found on entry level bikes have external cups.  The newer integrated style allows the bearings to sit directly against the frame for greater strength whilst saving weight.


The choice is between the traditional railed version or a newer pivotal style which uses a single bolt to give adjustability at the same time as saving weight.  Plastic pivotal seats will again save some weight. A minimalist option is an integrated seat and post combination. 

Seat posts  These vary in design according to whether the seat is the railed version. Pivotal types allow a wide range of adjustability while keeping the design clean and simple. Aluminium clamps to keep the seat post in place have anodized finishes and also chromoly for the most toughness.


There is considerable debate in BMX circles whether bikes for street and flatland riding should have any brakes at all. But people new to BMX should have at least a rear brake. 

Brake Levers

They provide the right response whether to modulate speed for a stunt or pull up hard.

Brake Pads

There is a vast choice of different lengths, different colours and different compositions for different weather and ground conditions.


Doing stunts involving twists can get also the brake cables in a twist and inhibit the movement. The gyro is a device that keeps cables straight and braking effective whatever the manoeuvre. 

How to Buy BMX Parts on eBay

Now that you've worked out which BMX parts you want, find them quickly on eBay. While you shop, don't forget Tyres & Wheels, Handlebars & Stems, Headsets, Drive, Pedals and Saddles & Seatposts. To start shopping, go to the Sports and Leisure category. Click the Sporting Goods portal and click Cycling.


The Categories list on the left side of each page will help you narrow down your listings by item type. You'll find links for Bikes, Bike Parts, Clothing, Footwear & Helmets, Cycling Accessories, Trophies and Other Cycling. As you refine your search you'll be able to narrow down your choice by subcategory.

Product Finder

Use the BMX Parts Finder to quickly narrow down item listings by type brand, model and condition. (New or used)

Keyword search

Search eBay listing titles for specific words. For example, if you want to find new BMX parts, type the keywords "BMX parts new" (without quotation marks) into the Search box. Click "Search title and description" to expand your results. Visit eBay's Search Tips page for more tips on searching with keywords.

If you can't find exactly what you want, try browsing eBay Stores or tell the eBay Community what you’re looking for by creating a post on Want It Now, or save a search on My eBay and eBay will email you when a matching item becomes available.

Buy BMX Parts with Confidence

Make sure that you know exactly what you’re buying and understand how eBay and PayPal protect you.

Know your item

Read the details in the item listing carefully.

Remember to add delivery costs to your final price. If you’re buying a high value item, check that the seller will insure it until it is delivered to you.

If you want more information, click the “Ask seller a question” button on the seller’s profile or the “Ask a question” link at the bottom of the item listing page.

Always complete your transaction on eBay (with a bid, Buy it Now or Best Offer) otherwise you will not be covered by eBay Buyer Protection.

Know your seller

Research your seller so that you feel safe and positive about every transaction.

  • What is the seller’s Feedback rating? 
  • How many transactions have they completed?
  • How many positive responses do they have?
  • What do buyers say in their Feedback? 
  • Are they positive about the seller?

Most top eBay sellers operate like retail shops and have a returns policy.

  • Do they offer a money-back guarantee?  
  • What are their terms and conditions?

Buyer protection

In the very unlikely event that you do not receive your item or it is not as described, eBay Buyer Protection your purchase price plus original delivery cost.


The essence of BMX is individuality. Everyone likes to have their bike set up in a different way. No one should worry if their selection of parts results in a set up that is different. They should rejoice.  With enough skill and judicious choice of parts, riders can use their bikes for a variety of disciplines - racing, street, jumping or just taking things as they come.

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