All the parts of a bike wheel play a vital role in overall performance and safety.

In this comprehensive guide, we’ll unravel the mysteries surrounding each part of a bike wheel, from the hub to the rim and everything in between.

Whether you’re a novice cyclist seeking to understand the basics or a seasoned rider delving deeper into wheel mechanics, join us as we explore each element’s function, materials, and importance.

From spokes to nipples, bearings to rims, this complete guide will equip you with the knowledge to optimize your cycling experience to the fullest!

Wheel Rim

The bike wheel’s rim is the outer circular component of a bicycle wheel, serving as the foundation for mounting the tire and providing structural support for the entire wheel assembly.

It consists of a hoop-shaped structure most commonly made from either aluminum (cheaper wheels) or carbon fiber (high-end wheels).

The rim’s inner surface features a bed where the tire’s beads sit, while the outer surface may include a braking surface if the wheel is designed to be used with rim brakes.

Rims come in various sizes, widths, and depths tailored to different riding disciplines and preferences, influencing factors like tire compatibility, aerodynamics, and overall wheel strength and performance.

The inside of a bike wheel rim, tubeless.

A mountain bike will have a wheel between 26” and 29” in diameter and will be fairly wide to accommodate wider tires. A road bike will usually have a 700c (29”) wheel rim, but it will be narrow for a thinner tire.

A smaller 16” wheel will be for a children’s or even a folding bike.

Wheels rims also come in different types to suit different tires. Here’s what you need to be mindful of:

  • Clincher – Inflatable inner tubes within an outer tire.
  • Tubeless – No inner tube needed, but can also be used with a clincher tire.
  • TubularSelf-contained sealed tires that are glued onto the rim with no inner tube.
  • Hookless Unique tubeless tires with flat rim bead.

You also have different aerodynamic profiles. Some wheel rims are very light and shallow for climbing hills, and others are very deep to gain an aerodynamic advantage. The size typically ranges from 25 mm to 100 mm; some are full disc wheels with no spokes.

Bikes Rim Key Variables

FactorWhat It Affects
Wheel Diameter Size Of The Rim
Bead Seat Diameter (BCD) Size Of The Rim Where The Tire Grips
Internal And External Rim Width For Tire Shaping And Compatibility
Rim Depth Aerodynamic Properties
Material Weight And Strength
Braking Disc Or Rim

Wheel Hubs and Freehubs

A hub on a bike wheel.
The hub of a bike’s front wheel.

Next, we have the wheel hub and freehub. This sits in the center of the wheel and allows the wheel to move while still safely mounted to the forks or the frame. They are typically made of aluminum, but performance versions are carbon fiber. 

They have bearings inside, allowing free movement. Hubs come in many shapes and sizes. They are different sizes not just for the spokes they hold but also for the axles they use.

All Parts Of A Bike Wheel Explained 1
The freehub of a bike’s rear wheel.

The rear and the front are completely different, with the rear having what we call a freehub.

It not only allows the wheel to freewheel while you’re coasting, but also has a ratchet system attached, so when you pedal, it can engage the rear wheel to propel you forward.

The parts of a rear bike wheel hub are completely different to the front and they are not interchangeable. 

Freehubs come in different speeds for different cassettes. For example, some freehubs might only have options for 7 to 10 speeds, and others might have options for up to 12 speeds.

The part of the freehub that the cassette slides onto is called the freehub body. These come in different designs according to brand and the number of speeds in the cassette, and are not always interchangeable.

Wheel Hub Key Variables

FactorWhat It Affects
Spoke Count Number of Spokes
Axle Size The Axle Compatibility
Freehub Type Brand Compatibility
Freehub Width Amount Of Speeds
Material Weight And Strength
Braking Disc Or Rim

Wheel Spokes And Nipples

A single red spoke on a bike wheel.
Bladed spoke on my road bike wheel.

Then we have the spokes and the nipples. These are what hold everything in the wheel together. The spokes connect to the nipples, holding the hub to the rim. You can adjust the spokes’s tension, which will straighten the rim to be “true”

There’s a lot more to spokes than you might think. First, they come in all different lengths, and some are made uniquely for a certain type of wheel depending on the rim depth and hub size. 

They also come in different widths. Typically, wider ones are stronger, and thinner ones are lighter. It’s important to understand that the parts of a rear bike wheel are different to the front and often cannot be swapped between.

They also attach in different ways. You have straight pull and J bend. The straight pull is used on performance wheels, and J bends are on more budget-friendly wheels.

You will also find that spokes come in different shapes, with some being bladed for aerodynamics and others butted for strength.

Wheel Spokes And Nipples Key Variables

FactorWhat It Affects
Spoke Length To Connect The Spokes And Hub
Spoke Gauge  Strength, Weight, And Compatibility 
Spoke Design Aero, Bladed, or Round
Attachment  J Bend Or Straight Pull
Material Aluminum Or Carbon Fiber

Skewers And Axles

A front hub on a bike wheel with a skewer inside.

The skewer and axles are the components that hold the wheel in the bike frame. They go through the hub center, where the bearings are. When it comes to axles, there are a few different types, and it’s good to know about them.

On classic bikes, you had a bolt-through axle with 15 mm nuts on the end, which you undid to release the wheel. Then, it progressed to quick release, which you can take apart by just using your hands. The most modern solution is the thru-axle, which uses an Allen key.

The best option is really the thru-axle, especially if using disc brakes. They are bigger and stronger and always ensure the wheels return to the correct position. 

Tires

A large slick city tire on a bike.

Finally, we have the tubes and tires which is a very interesting part of a bike wheel. This is what goes on the outside of the rim and connects to the floor. The tires are your point of traction and make a huge difference to the bike’s speed and performance.

Tires come in all different shapes and sizes. You typically use two measurements: the BCD, which is the bead seat diameter, and the width. The tires must match the rim’s BCD and be within the required width range.

Tires also vary depending on the terrain they are designed for. There are knobbly tires for mountain biking, small slick tires for road cycling, and fast-rolling off-road tires for gravel cycling.

Tires need to be inflated with air, and most bikes use inner tubes or a tubeless system with a sealant. The only exception is tubular, where the tire and the tube are just one single piece or a solid tire.

Bike Tires Key Variables

FactorWhat It Affects
Size Overall Diameter And Width
Tread Pattern Road, Gravel, Or Off-Road
Rim Type Clincher, Tubeless, Hookless, Tubular
Compound  What They Are Made Of

Disc Or Rim Brake Wheels

A rim brake bike brake.

Another very interesting factor is either disc or rim brakes. Wheels have to have the correct braking system for the bike. You can only use disc brake wheels if you have a disc brake bike. A rim-brake bike can only work with rim-brake wheels.

Disc Brake Wheels 

Disc brake wheels have a large rotor in the center of the wheel attached to the hub, and the bike’s calipers grab these. They are excellent in poor weather conditions and are very powerful, a must have on an off-road bike.

They come in two versions, hydraulic or mechanical, and most modern bikes use them. It’s the way the industry is going, and with replaceable rotors, it means they last much longer than rim brake wheels.

Rim Brake Wheels

Rim brakes were very popular about a decade ago and were used on many types of bikes, but in recent years, we have seen fewer and fewer of them. The wheel has a braking surface on the rim, and the caliper on the bike grips it to slow it down. 

Rim brakes are not great in poor weather conditions, and after lots of use, the rim needs replacing, which often turns out cheaper to replace the wheelset itself. Rim brakes are incredibly light and easier to work on and repair.  

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