Wheels Sizes, Compatibility And Fitting

Wheel size compatibility

Understanding wheel sizes

Bicycle wheels come in a variety of sizes, each suited for different types of riding. The most common wheel sizes include:

1. 700c: Commonly found on road bikes, cyclocross bikes and hybrids.
2. 26 inches: Traditionally used on mountain bikes, though it's less common now.
3. 27.5 inches (650b): A newer size that's become popular for mountain biking.
4. 29 inches: Another mountain bike standard, particularly for cross-country riding.
5. 20 inches: Typically used on BMX bikes and some folding bikes.
6. 24 inches: Found on some BMX bikes, youth bikes, and small adult bikes.
7. 650c: Used on some triathlon and road bikes, particularly for smaller riders.

These sizes refer to the diameter of the wheel, but understanding what that diameter means in practice requires more context.

How Wheel Size Affects Your Ride

The size of your bike's wheels affects several aspects of your ride, including:

1. Rolling resistance: Larger wheels generally have lower rolling resistance, meaning they require less effort to keep moving. This is why road bikes typically have larger wheels, such as 700c.
2. Acceleration: Smaller wheels can accelerate faster because they have less rotational inertia. This is particularly beneficial in BMX racing or city commuting where frequent stops and starts are common.
3. Manoeuverability: Smaller wheels offer greater manoeuverability, making them ideal for technical mountain biking or navigating tight urban spaces.
4. Ride smoothness: Larger wheels can roll over obstacles more easily, providing a smoother ride over rough terrain. This is one reason why 29-inch wheels are popular for cross-country mountain biking.
5. Fit and comfort: The size of your wheels also impacts how your bike fits your body. Smaller riders may find it more comfortable to ride bikes with smaller wheels.

700C

It used to be oh-so-simple only a few years ago, shallow-section alloy rims taking a standard 23mm road tyre were the 90% norm. But then...aerodynamics and comfort came into play.

1. Aerodynamics: deeper section wheels tend to increase speed in non-crosswind, flatter conditions.

1. Comfort: bike manufacturers have been steadily increasing tyre-clearance even on race bikes. Wheels have been getting wider, to take wider tyres. So, if you have an older bike and are looking for a wheel upgrade, take care that the new wheels (and wider tyres) will fit your older bike. And that they not only fit under no load (in a workstand) but also tolerate load, as even the best wheels will flex a little on steep hills / high load. If in doubt, please contact us for advice, we have a comprehensive knowledge of bikes going back a long way.
2. 650B: some gravel bikes will take either a 700C or a 650c (27.5 wheel). Check your bike specs.
3. Axle system: rim brakes are invariably quick release. No problem here. Disc braked bikes started off being the same quick release but most are now thru axle,
4. Disc compatibility: Centerlock or 6 bolt disc/rotor attachment. Some wheels come with adaptors to allow for fitting either. Worst case, you might need to allow for some new rotors eg if the new wheels are Centerlock fitment and but your discs are 6 bolt. The Centerlock system is much better and is becoming the industry-standard.
5. Tubeless: rims can be (a) not compatible with tubeless (b) hookless = tubeless only (c) 2 way fit - will accept a tubeless or non-tubeless tyre.

1. Cassette type: yours is most-likely a Shimano HG fitment but it could also be Shimano Micro Spline, Campagnolo or SRAM XD/XDR. Oh, and you might also need to ensure freehub body cassette ratio compatibility, an 8/9/10 speed freehub won't accept an 11- or -12-speed cassette. But it generally will the other way round.

Thru Axles

Thru-axles have become a standard in the cycling world, particularly in high-performance road, gravel, and mountain bikes. They offer several advantages over the traditional quick-release (QR) skewers, providing improved rigidity, safety, and handling. This guide will delve into what thru-axles are, their benefits, how they differ from quick releases, and how to choose the right thru-axle for your bike.

What is a Thru-Axle?

A thru-axle is a type of axle that passes through the frame or fork of the bicycle and the wheel hub, effectively locking the wheel into place. Unlike traditional quick-release skewers, which clamp the wheel to the dropouts, thru-axles screw directly into the frame or fork, providing a more secure connection.

Key Features of Thru-Axles:

1. Diameter: Thru-axles are thicker than quick-release skewers, typically ranging from 12mm to 15mm in diameter for road and mountain bikes, respectively.
2. Threading: Thru-axles are threaded at one end and screw into a corresponding thread in the dropout.
3. Length: The length of a thru-axle is specific to the bike's frame and fork, ensuring a precise fit.

Common Sizes:

1. 12mm x 100mm: Standard for road bikes and gravel bikes (front axle).
2. 12mm x 142mm: Standard for road and gravel bikes (rear axle).
3. 15mm x 100mm: Used on mountain bikes, especially older models (front axle).
4. 15mm x 110mm (Boost): Common in modern mountain bikes for added stiffness (front axle).
5. 12mm x 148mm (Boost): Standard on modern mountain bikes for the rear axle, offering more rigidity.

Advantages of Thru-Axles

Thru-axles offer several advantages over traditional quick-release systems, particularly in terms of rigidity, alignment, and safety.

a. Rigidity and Stability

Thru-axles provide a stiffer connection between the wheel and the frame or fork, which enhances overall bike stability. This is particularly important in high-performance cycling disciplines like mountain biking, where the terrain is rough and demands greater control.

1. Improved Handling: The increased stiffness reduces flex in the wheel, which improves handling, especially when cornering or descending at high speeds.
2. Enhanced Power Transfer: With less flex, more of your pedalling power is transferred directly to the road or trail, improving efficiency.

b. Improved Wheel Alignment

Thru-axles help ensure that the wheel is perfectly aligned in the frame or fork every time you install it. This is crucial for consistent braking performance, particularly with disc brakes, where even a slight misalignment can cause rubbing or uneven wear.

1. Consistent Brake Alignment: Because the axle passes directly through the hub and the dropout, the rotor is always perfectly aligned with the caliper, minimizing brake rub.
2. Easier Wheel Changes: With thru-axles, there’s less chance of misaligning the wheel during installation, making wheel changes quicker and more foolproof.

c. Increased Safety

Thru-axles are inherently more secure than quick-release skewers. Because they thread directly into the frame or fork, there's no risk of the axle coming loose while riding, which can happen with improperly secured quick releases.

1. Reduced Risk of Wheel Detachment: The thru-axle’s secure connection significantly reduces the risk of the wheel coming out of the dropouts, especially under heavy braking or during riding.

Thru-Axle vs. Quick Release: Key Differences

While both thru-axles and quick releases serve the same basic function of securing the wheel to the bike, there are several key differences between the two systems.

a. Mechanism

1. Quick Release: A quick-release skewer uses a cam lever to clamp the wheel into the dropouts. It’s a relatively simple system that’s easy to use but relies on the rider properly securing the lever.
2. Thru-Axle: A thru-axle screws directly into the frame or fork, providing a more positive and secure engagement. It typically requires a tool (often a 5mm or 6mm hex wrench) to install and remove, though some models feature a built-in lever.

b. Axle Diameter

1. Quick Release: Typically 9mm in diameter for the front and 10mm for the rear, which is relatively thin compared to thru-axles.
2. Thru-Axle: Much thicker, typically 12mm or 15mm, which increases stiffness and durability.

c. Weight

1. Quick Release: Generally lighter due to the simpler mechanism and thinner skewer.
2. Thru-Axle: Heavier, but the added weight is offset by increased performance benefits in terms of stiffness and handling.

d. Compatibility

1. Quick Release: Found on older road bikes, some entry-level mountain bikes, and many commuter bikes.
2. Thru-Axle: Standard on modern mountain bikes, gravel bikes, and road bikes, especially those with disc brakes.

How to Choose the Right Thru-Axle for Your Bike

Choosing the correct thru-axle for your bike is crucial for ensuring compatibility and performance. Here are the main factors to consider:

a. Axle Diameter

1. 12mm: Standard for road and gravel bikes. Offers a good balance of weight and stiffness.
2. 15mm: Common on mountain bikes, especially for front wheels, providing extra rigidity.
3. 15mm (Boost): Used on modern mountain bikes for front wheels to accommodate wider hubs.

b. Axle Length

The length of the thru-axle needs to match the specific requirements of your bike's frame or fork. It's important to measure the distance between the inside surfaces of the dropouts to ensure you get the correct length.

c. Thread Pitch

The thread pitch of the thru-axle (the distance between threads) must match the thread in the dropout. This can vary between different brands and models, so it’s essential to check your bike’s specifications or consult with the manufacturer.

d. Lever or Tool-Required

Some thru-axles come with a built-in lever for tool-free operation, while others require a hex wrench or another tool. Lever-equipped thru-axles are more convenient for quick wheel changes, but some riders prefer the cleaner look and potentially more secure fit of a tool-required axle.

e. Compatibility with Hub

The thru-axle diameter must match the diameter of your hub. Most modern hubs are designed to work with thru-axles, but it’s always a good idea to double-check compatibility.

Installation and Maintenance of Thru-Axles

Proper installation and maintenance of thru-axles are crucial for ensuring their longevity and performance.

a. Installation

1. Align the Wheel: Start by ensuring that the wheel is properly seated in the dropouts. This is easier with thru-axles because the design naturally guides the wheel into the correct position.
2. Insert the Axle: Slide the axle through the dropout and hub, ensuring it’s threaded correctly on the other side.
3. Tighten: Use the appropriate tool or the built-in lever to tighten the axle until it’s secure. Don’t overtighten, as this can damage the threads or the axle itself.

b. Regular Checks

1. Torque: Periodically check the torque on the thru-axle to ensure it’s properly tightened according to the manufacturer’s specifications.
2. Cleanliness: Keep the axle and the threads clean to prevent dirt or grit from interfering with the threading or causing wear.
3. Lubrication: Lightly lubricate the axle threads periodically to ensure smooth operation and prevent corrosion.

Transitioning from Quick Release to Thru-Axles

If you’re upgrading an older bike that uses quick releases to a thru-axle system, there are a few considerations:

a. Frame and Fork Compatibility

The first step is to determine whether your current frame and fork are compatible with thru-axles. Most modern frames and forks designed for disc brakes are thru-axle compatible. However, if your bike was originally designed for quick releases, it may not be possible to convert it to thru-axles without replacing the frame and fork.

b. Adapters

There are adapter kits available that allow some quick-release hubs to be converted to work with thru-axles, but these are typically a compromise and may not provide the same performance benefits as a true thru-axle system.

c. Wheel Compatibility

Ensure your wheels are compatible with thru-axles. If not, you might need new wheels that can accommodate the larger axle diameter. Some hubs can be converted to work with thru-axles by swapping out the end caps, but this depends on the specific hub model.

Mountain bike wheels

In addition to the above (wheel/tyre width, tubeless, axle type) there is also the issue of wheel size and wheel size compatibility. For example, a 29eR wheel will almost certainly not fit an older 26 inch wheel frame. You might get away with fitting a 29eR wheelset to a 27.5 inch framed bike, albeit to the detriment of the geometry and handling of the bike. To really complicate matters, full suspension MTB manufacturers have been playing around with 'mullet' configurations in the last few years, with a 29eR up front and a 27.5 Plus at the back, to optimize turn in speed and grip respectively.

Wheel fitting service

So, all said (well done for getting this far), you might want to contact us first!

And you might want to use our wheel fitting service to make sure the job is done properly and that everything is compatible. We quote on a per job basis, generally at £48 per hour including VAT. Bear in mind we can get a lot done in an hour!

Some considerations:

1. rim braked bikes - carbon rims require special brake pads (which come with your new wheels), these must be fitted as they are very different to the brake pads that are used on alloy rims.
2. tubeless setup - can try even the most patient! Maybe leave it to us, we use the best sealants and can advise on rim / tyre compatibilities.
3. cassette and rotor fitment - you'd be surprised how many have-a-go-at-home fitments go wrong.