Bicycle Hub Spacing Explained: OLD, Axle Standards, and Compatibility

Choosing a bicycle hub for a custom wheel build involves more than selecting the correct number of spoke holes.

The hub must physically fit the bicycle’s frame or fork, and its dimensions must work with the rest of the wheel components.

One of the most important specifications is hub spacing, often referred to as OLD.

Understanding hub spacing can prevent one of the most frustrating wheel-building mistakes: building a wheel around a hub that doesn’t fit the bicycle.

What Is Bicycle Hub Spacing?

Hub spacing is the distance between the outer faces of the hub’s locknuts, end caps, or equivalent contact points where the hub fits into the bicycle frame or fork.

This measurement is commonly called OLD, which stands for Over Locknut Dimension.

The hub’s OLD needs to match the frame or fork spacing.

If it doesn’t, the wheel may not fit correctly.

Why Is Hub Spacing Important?

Hub spacing affects:

  • Whether the wheel fits the frame
  • Whether the axle fits correctly
  • Hub and frame compatibility
  • Spoke geometry
  • Spoke length
  • Wheel dish
  • Brake rotor positioning
  • Cassette positioning

For a custom wheel build, accurate hub specifications are essential.

Front Hub Spacing

Front hubs are generally simpler than rear hubs because they don’t need to accommodate a cassette.

However, several front hub standards exist.

Older and traditional bicycles may use narrower quick-release configurations, while many modern bicycles use wider thru-axle systems.

Always check the fork manufacturer’s specifications before choosing a hub.

Rear Hub Spacing

Rear hubs are more complicated.

The rear hub must accommodate the drivetrain, cassette or freewheel, and the frame’s axle spacing.

The position of the flanges is also important because it affects spoke geometry and wheel dish.

Modern rear hubs are available in several different spacing standards.

What Is a Thru-Axle?

A thru-axle passes through the frame or fork and secures the hub directly.

Thru-axle systems are common on modern road, gravel, mountain, and e-bike applications.

The axle diameter and hub spacing must both be compatible with the frame or fork.

A hub that has the correct spacing but the wrong axle interface may still be incompatible.

What Is a Quick-Release Hub?

Traditional quick-release hubs use an axle that fits inside the frame or fork while a separate quick-release skewer secures the wheel.

These systems are still common on many bicycles.

When replacing or building a wheel for a quick-release bicycle, verify the hub’s intended axle configuration.

Hub Spacing Is Not the Same as Flange Spacing

This distinction is important.

Hub spacing refers to the distance between the hub’s frame or fork contact points.

Flange spacing refers to the location of the spoke flanges relative to the hub centerline.

Flange spacing is critical when calculating spoke length and evaluating wheel geometry.

A hub can have the correct OLD but still have different flange dimensions from another hub with the same spacing.

Why Hub Flange Position Matters

The position of the hub flanges influences the spoke bracing angle.

Generally, a wider flange position can provide a more favorable spoke angle.

However, hub geometry is constrained by the drivetrain, brake rotor, bearings, and axle design.

Rear wheels are particularly asymmetric because of the cassette.

This is one reason rear wheel spoke tension and geometry can differ significantly from the front wheel.

Hub Spoke-Hole Count

The hub’s spoke-hole count must match the rim.

For example, a 32-hole hub is normally paired with a 32-hole rim.

The same applies to 24-hole, 28-hole, 36-hole, and other configurations.

Never assume that spoke count can be changed simply by using a different lacing pattern.

Hub Compatibility With Disc Brakes

Disc brake hubs include a mounting interface for the brake rotor.

Different rotor mounting systems exist, so the hub must be compatible with the intended brake system.

The hub’s rotor position also influences the overall wheel geometry.

Freehub Body Compatibility

Rear hubs can use different freehub body standards.

The freehub body must be compatible with the cassette you intend to use.

This is particularly important when building a replacement rear wheel.

Before ordering a hub, verify:

  • Freehub standard
  • Cassette compatibility
  • Axle type
  • Hub spacing
  • Rotor interface
  • Spoke-hole count

Hub Measurements You Need for Spoke Length

When calculating spoke length, hub spacing alone isn’t enough.

You will generally need:

  • Hub flange diameter
  • Left flange distance from center
  • Right flange distance from center
  • Spoke-hole count
  • Spoke-hole diameter
  • Lacing pattern

These measurements are used together with the rim’s ERD to determine the correct spoke length.

For more information, see our Bicycle Spoke Length Calculator Guide.

How Hub Choice Affects Wheel Dish

Hub geometry can affect wheel dish.

Rear wheels are a common example because the cassette forces the drive-side flange closer to the wheel centerline.

This creates an asymmetric spoke arrangement.

Understanding hub flange position can help explain why one side of a wheel may require different spoke tension or a different spoke length.

How to Choose the Right Bicycle Hub

Before purchasing a hub, identify the bicycle’s requirements.

Step 1: Determine Frame or Fork Spacing

Measure or verify the manufacturer’s specification.

Step 2: Identify the Axle Type

Determine whether the bicycle uses:

  • Quick release
  • Thru-axle
  • Another axle system

Step 3: Check Spoke Count

Match the hub to the intended rim.

Step 4: Check Brake Compatibility

Verify the rotor mounting system if you’re building a disc-brake wheel.

Step 5: Check Drivetrain Compatibility

For rear wheels, verify the freehub body and cassette compatibility.

Step 6: Gather Flange Measurements

You’ll need these for accurate spoke-length calculations.

Common Hub Selection Mistakes

Some of the most common mistakes include:

  • Choosing the wrong OLD
  • Confusing axle diameter with hub spacing
  • Ignoring flange dimensions
  • Selecting the wrong freehub body
  • Using the wrong spoke-hole count
  • Forgetting brake rotor compatibility
  • Assuming two hubs with the same spacing have identical geometry

Checking specifications before purchasing components can save considerable time and expense.

Shop Bicycle Hubs and Wheel Building Components

WheelBuildingParts.com offers a selection of bicycle hubs for custom wheel builds.

Complete your build with compatible bicycle spokes and bicycle wheel nipples.

Final Thoughts

Hub spacing is one of the first specifications you should verify when planning a custom bicycle wheel.

The correct hub needs to fit the frame or fork, match the axle system, accommodate the drivetrain and brakes, and provide the appropriate spoke-hole count and flange geometry.

Once you know the hub’s dimensions, you can combine them with the rim’s ERD and your chosen lacing pattern to calculate the correct spoke length.

Getting the hub selection right at the beginning makes the rest of the wheel-building process much easier.