The bicycle frame is the central component of any bicycle, to which the handlebar, saddle and wheels are all fitted. Over the course of the development of the bicycle, the frame has seen a number of different designs and has been built from a number of different materials. The design familiar to most modern cyclists, the diamond frame, owes its origin to the safety bicycle.
The first kind of bike to have two equally sized wheels emerged in the late nineteenth century, and were marketed as a safer alternative to the more prevalent penny farthing bicycles of the time. There key characteristics that a cyclist should consider before purchasing a new bicycle frame are the design, material and size of the frame. A wide range of different bicycle frames can be found on eBay.
Bicycle Frame Structure
- Modern bicycle frames are made up of a number of interconnecting tubes. The shape and positioning of these tubes constitutes different variations of frame design. When considering a new frame, it is important to make sure that the particular design of a frame is suitable for the kind of riding it is intended for. A bike frame is made up of:
- The cross bar, sometimes referred to as the top tube, runs parallel to the ground and connects the seat tube with the head tube. Control cables, such as those for breaks and gears, are often mounted along or inside this tube.
- The head tube is where the handlebar is connected. This connects the handlebar with the front wheel fork, allowing the rider to steer the bike.
- The down tube is the downward sloping tube that connects the head tube to the bottom bracket shell, the lowest point on the bike frame near the pedals. Accessories such as bottle cages are often mounted here.
- The seat tube, which runs from the bottom bracket shell up to the seat. The height of the seat is adjusted by changing how far into the seat tube the seat post is inserted. There will generally be a clearly marked minimum insertion level, showing the minimum the seat post can be inserted and remain safe for use.
- The seat stays connect the top of the seat tube to the rear wheel fork.
- The chain stays connect the bottom bracket shell to the rear wheel fork. These run parallel with the bicycle chains and can vary in shape to allow extra space for wheels, changes of the heels of the rider.
- The bottom bracket shell is the lowest point of the frame, and the down tube, chain stays and seat tube all connect here.
Bicycle Frame Designs
The most commonly available design of bicycle frame is the ubiquitous diamond frame. This kind of frame is made up of two ‘triangles’, a larger triangle at the front consisting of the tube, head tube, down tube and top tube, while a smaller rear triangle is made up of the seat tube, seat stays and chain stays. The geometric construction of this design results in a sturdy frame while reducing the amount of materials necessary, reducing both the weight and cost of the frame.
A popular alternative to the traditional diamond frame is the step through frame. Originally designed to allow female riders who wore skirts to more easily mount and dismount the bicycle, this design has a considerably lower, or completely removed, cross bar. This design became a popular choice for a wide range of cyclists who, for whatever reason, prefer a more accessible bicycle.
A further advantage of this design is that it is potentially safer in the event of a cyclist losing balance, as the cyclist can step through the frame with reduced risk of becoming entangled. However, such frames can often be heavier than standard diamond frames, making this design a more popular choice for less performance oriented bicycles, such as the town bike.
Particularly in the case of more performance oriented bicycles, frames may have small variations in the geometry of their construction depending on the kind of cycling they are intended for. There are a number of key measurements which are altered to achieve this.
- The height of the saddle.
- The reach, the distance from the saddle to the handlebar.
- The drop, the vertical distance between the saddle and the handlebar.
- The setback, the distance between the front of the saddle and the bottom bracket.
- The stand over height, the distance of the top tube from the ground.
- Toe overlap, the amount the feet can come into contact with the front wheel.
Different design variations of frame make them more suitable to certain kinds of bicycle. Such frames will often be referred to by the kind of bicycle they are intended for, for example, a ‘road bicycle frame’.
The road bike frame, designed for road racing bicycles, offers two variations. Traditional geometry diamond frames are generally seen as more comfortable and stable. The longer ‘wheelbase’, the horizontal difference between the centre of the front and back wheel, contributes to shock absorption and enhances comfort. The compact geometry diamond frame offers a lower centre of gravity. This, combined with a shorter wheelbase and smaller rear triangle, gives the bike more responsive handling.
The track bicycle is designed for indoor racing on specifically designed tracks. Like the road bike, the emphasis is on speed and aerodynamics. A frame designed for track racing will often have a steeper seat tube which puts the rider in a more aerodynamic position.
The utility bicycle is designed to carry cargo, and as such the emphasis is on sturdy construction and comfort. Frames designed for use in this kind of bike are often built to position the rider in a comfortable, more upright riding position.
Mountain bike frames are designed to tackle rough terrain at high speeds. Steeper angles, with the seat tube closer to 90 degrees, are often preferred for uphill riding, as they allow for more efficient pedalling and superior handling. Less steep angles are often preferred for downhill riding, due to the greater stability they offer at higher speeds. Some mountain bike frames may come with inbuilt suspension.
Town bicycles are primarily built for short duration and leisure riding, and as such are not built for speed. Step through frames are a popular choice for town bicycles, and the rider is often position in a comfortable, upright position.
Hybrid bicycles vary widely, combining the characteristics of different kinds of bikes. They are popular for use in more heavily urbanised areas, and are generally based around mountain bike frames.
The material out of which a bicycle frame is constructed is one of the key characteristics to consider when purchasing a frame. The material used can greatly affect the feel of the ride, as well as the cost of the frame. Important characteristics of materials to consider include their weight, strength, durability and cost. The importance of each of these will vary depending on the cyclist and their intended use of the frame. A town bike, for example, has greatly different requirements to a high performance racing bike.
Steel is one of the oldest materials used in the construction of bicycle frames, meaning that steel frames are widely available. While specific price can vary on the kind of steel used and the way the frame was built, steel frames are generally the cheapest available.
They also offer a good deal of strength, and can bend in the event of a collision without losing much of this strength. Some cyclists find steel frames to offer a more comfortable ride, as the less rigid frame offers a degree of shock absorption. The key drawback of steel is its greater density compared to other commonly used materials, meaning that steel frames are often heavier.
This makes steel frames less appropriate for bicycles which benefit from a lighter weight, such as racing track and road bicycles. However, the cheap cost and greater ride comfort make them a popular choice for bicycles which place emphasis on comfort. If properly protected from rust and corrosion, steel frames can last for a long time.
Aluminium has come to replace steel as the most popular material choice for modern bicycle frames. While sometimes slightly more expensive than steel, aluminium remains an affordable and widely available choice, offering a great degree of strength for its lighter weight.
Aluminium frames are sometimes considered less comfortable than steel, as the rigid frames offer less shock absorption than steel. However, some cyclists prefer the more rigid feel of the aluminium bike.
Aluminium frames also suffer fatigue at a great rate than steel, though can still last between five and ten years of use, and though are resistant to corrosion. The affordability and light weight are the key benefits of aluminium frames, and the material is used in a wide range of bicycles, including performance focused racing bicycles, mountain bikes and hybrid bikes.
Carbon fibre frames are an unusual but increasingly popular choice of frame material. Carbon fibre frames are both very strong and very light. This material can also be specifically tailored to the needs of the frame, making certain points of the bicycle stronger to withstand pedalling and others more flexible to enhance comfort.
However, carbon fibre frames are considerably more expensive than alternatives such as aluminium and steel. Additionally, carbon fibre is a brittle material and prone to cracking, and carbon frames are often designed to bend to alleviate this. The expense means that carbon frames are often only suitable for cyclists who place a priority on performance, making them suitable for high level racing bicycles.
It is becoming increasingly common to find carbon components, such as wheel forks, on aluminium frames, giving some of the strengths of carbon components at a more affordable price.
Titanium is an expensive and exotic choice of frame material. Titanium is both exceptionally light and strong, and combines a number of desirable characteristics such as durability and resistance to corrosion.
Due to the difficulty of working the metal, titanium frames are among the most expensive available, putting them out of the price range of many cyclists. Titanium frames are therefore most suitable for very high end racing and mountain bikes.
Sizing a Frame
While variables such as seat height can be changed by the rider, it is still important to correctly size a frame to the cyclist. A correctly sized bicycle frame can mean a safer, more enjoyable riding experience.
- The ‘bicycle inseam’ measurement is used to fit a rider to a frame. This is a shorter measurement than the trouser inseam, and is measured from the bottom of the rider’s crotch to the floor.
- This measurement should be compared to the seat tube length of the frame, which is generally available on the item’s entry. A 54cm size frame, for example, means that the tube measures 54cm from where the pedals will be installed to the top, where the seat will be fitted. Generally, there should be a few inches space between the top of the frame and the rider’s crotch; more if the frame is intended for use over rough ground.
Some manufacturers measure their frames in different ways, and offer their own sizing guides. This means it is a good idea to refer to the manufacturer or seller of a particular frame in order to best size up a frame.
Finding a Frame on eBay
eBay offers a wide selection of bicycle components, including a range of bicycle frames of different materials and designs. The listing of available items can be accessed in the Cycling Section of the Sporting Goods portal. It is possible to browse the entire listing of bike frames in the Bike Parts section. Here the full listing of available can be browsed, and arranged with filters such as condition, frame material, frame manufacturer, the type of bike the frame is intended for, price and others.
Key information about the frame, such as the material it is made of, will generally be clearly displayed in the item’s listing, making it easy to see whether a particular frame matches the desired requirements quickly and easily. Further information can be found on the seller’s page, along with information about the seller such as feedback ratings and user reviews. It is also possible to ask the seller a question about the item here.
To find a specific frame, it may be easier and more effective to use the search function available at the top of every page. The Search Tips page offers further information on effectively using eBay’s search function.
The frame is the core component of any bike, and it is important to match the design, material and construction of a frame to the cyclists needs. A well made frame of the right material and design can greatly improve the cycling experience, as well as greatly impact the durability of the bike. It is important to find the right frame, and eBay offers a wide, accessible range.