Classic K’NEX Wheels

Last checked: August 24, 2026

Classic K’NEX wheels come in many sizes and designs, from very small wheels to large, wide, narrow and Huge wheels.

A K’NEX wheel is not always a single part. Many wheels consist of a plastic hub or wheel center fitted with a separate tire (tyre). Some hubs can also be used without a tire, while other K’NEX wheels are complete or use another K’NEX part as their wheel center.

This means that the diameter of a hub is not necessarily the outside diameter of the completed wheel.

Three familiar Standard Classic wheel sizes illustrate this:

Hub / wheel center	Tire	Approx. complete diameter
37 mm	Small tire	45–47 mm
50 mm	Medium tire	65 mm
50 mm	Large tire	90–92 mm

The exact outside diameter can vary with the tire design and tread.

Terminology: K’NEXCHANGE uses American English (tire, gray, center). Documented K’NEX part names may use British spellings such as tyre, grey and centre. Original documented names are retained where useful for identification.

Very small wheels and 18 mm hubs

K’NEX produced several very small wheel components. Some 18 mm hubs occur in both Classic and Micro K’NEX applications.

Known examples include:

Documented name	Part no.
Hub 18mm Grey	531204
Hub 18mm Yellow	531205
Hub 18mm Light Grey	99106L

Additional colors are known. Some K’NEXCHANGE/AQ records use unique Ecwid item numbers, so these should not automatically be interpreted as original K’NEX part numbers.

Small tires documented in this size range include:

Documented name	Part no.
Tyre 21mm Blue	99105B
Tyre 21mm Green	99105G
Tyre 21mm Red	99105R
Tyre 21mm Yellow	99105Y
Tyre 21mm Ribbed	99105N
Tyre 21mm Smooth	99189
Tyre 21mm Soft	99176
Tyre 30mm Black	531300

Not every tire in this size range should automatically be assumed to fit every small hub. Known combinations should be identified separately where confirmed.

25 mm wheels

Two small black 25 mm wheel designs are documented:

Documented name	Part no.
Wheel 25mm Open centre Black	91140
Wheel 25mm Closed centre Black	918300

The open-center and closed-center designs are visibly different and can therefore be distinguished even when the part number is unknown.

Plane and other small specialty wheels

Some small wheels were designed for particular models or applications rather than as part of the regular Standard wheel range.

One documented example is:

99888 — Wheel small for Plane

This small black wheel is associated with Plane Building Set 17034.

Other special-purpose small wheels can be added to this section when reliably identified.

Standard Small wheels — 37 mm hub / about 45–47 mm wheel

One of the traditional Classic K’NEX wheel systems uses a plastic hub of approximately 37 mm.

Known Hub/Pulley variants include:

Documented name	Part no.
Hub/Pulley Small Silver	90978
Hub/Pulley Small Grey	90978G
Hub/Pulley Small White	909782

The corresponding Standard Small tire is:

91975 — Tyre Small

With the tire fitted, the complete wheel is approximately 45–47 mm in outside diameter.

The name Hub/Pulley is significant. This plastic part is not restricted to use as a wheel center. It can also be used without a tire as a pulley or for other suitable functions.

37 mm spoked wheels

K’NEX also produced dedicated spoked wheel centers in this size range.

Documented name	Color	Part no.
Hub Spoked 37mm	Silver	91978
Hub Spoked 37mm	Black	919780
Wheel 37mm Narrow	Red	20301

20301 is a dedicated red spoked wheel center. Although its documented name uses the word Narrow, its spoked construction is clearly visible.

These parts should not be confused with a Classic 8-way connector used as the center of a wheel.

A suitable tire can increase the outside diameter of a 37 mm wheel center to approximately 45 mm, depending on the combination used.

Connector-based wheels — about 43 mm

Some small K’NEX wheels use a regular Classic 8-way connector as the wheel center, with a tire fitted around it.

Documented combinations include:

Documented name	Center color	Part no.
Wheel 43mm Blue	Blue	908003W
Wheel 43mm Orange	Orange	908004W
Wheel 43mm Silver	Silver	908005W

These are fundamentally different from the dedicated 37 mm spoked wheel centers.

The individual 8-way connector remains a Classic Connector. Its use as a wheel center demonstrates how a K’NEX part can perform more than one function.

Because Classic 8-way connectors exist in additional colors, builders can make other color combinations even where these are not documented as separate complete wheel part numbers.

Other 43 and 44 mm wheels

Not every wheel with a similar outside diameter uses the 8-way connector construction.

Known examples include:

Documented name	Part no.
Wheel 43mm Red/Black	23483
Wheel 44mm	23481

These have their own designs and should not be treated simply as additional color variants of the 8-way connector wheels.

Racing wheels — 37 mm

The 37 mm Racing system uses a dedicated Racing hub and separate tire.

Known hubs include:

Documented name	Part no.
Hub Racing wheel 37mm Black	91170
Hub Racing wheel 37mm Grey	91174

Two different tire types are documented:

Documented name	Part no.
Tyre Racing wheel 37mm	91150
Tyre Racing wheel Slick 37mm	91380

The Slick tire has a visibly smoother running surface than the regular Racing tire.

Standard Medium wheels — 50 mm hub / about 65 mm wheel

The traditional Medium Classic wheel uses a larger Hub/Pulley of approximately 50 mm.

Known variants include:

Documented name	Part no.
Hub/Pulley Medium Silver	90979
Hub/Pulley Medium Grey	90979G

Medium tires include:

Documented name	Part no.
Tyre Medium	90976
Tyre Medium	91976

A 50 mm hub fitted with a Medium tire produces a complete wheel of approximately 65 mm.

A documented complete version is:

91976W — Wheel Medium 65mm

As with the smaller Hub/Pulley, the 50 mm plastic center can also be useful without a tire, including as a pulley.

Narrow wheels — 50 mm hub / about 60 mm wheel

Narrow wheels use a different 50 mm wheel center.

Known examples include:

Documented name	Part no.
Hub Narrow 50mm Grey	91254
Hub Narrow 50mm Black	91254B
Tyre Narrow Black	91240

With the Narrow tire fitted, the complete wheel is approximately 60 mm in outside diameter.

Another documented part is:

24041 — Wheel 50mm Narrow Black

The exact relationship between differently documented Narrow wheel combinations should be retained rather than assuming that every similar name represents the same individual part.

Racing wheels — 50 to 60 mm

The larger Racing system includes:

Documented name	Part no.
Hub Racing wheel 50mm	91184
Tyre Racing wheel 50mm	91160
Racing wheel 60mm	91160W

As with the smaller Racing wheels, the hub and tire are distinct components where separately documented.

Other wheels around 50 to 60 mm

Several other Classic K’NEX wheels occur in this size range.

Known examples include:

Documented name	Part no.
Wheel 50mm Chrome	99126
Wheel 58mm Chrome	99127
Wheel 60mm	23491

These should not automatically be treated as Standard, Racing or Narrow wheels merely because their diameters are similar.

Standard Large wheels — about 90–92 mm

A particularly useful feature of the Standard Classic system is that a compatible 50 mm wheel center can be fitted with a much larger tire.

The regular Large tire is:

91977 — Tyre Large

This creates a complete wheel of approximately 90–92 mm, depending on the combination and measurement method.

A documented complete version is:

91977W — Wheel Large 92mm

This means that similar 50 mm wheel centers can be used to create substantially different complete wheel sizes depending on the tire fitted.

Large hard-plastic tire

K’NEX also produced a hard-plastic version:

3310029 — Tyre Large Plastic

This is physically different from the flexible Large tire and should therefore be treated as a distinct tire type, not simply as another color.

Both the material and the tread/design can be useful identification features.

Chrome wheels

Chrome-finish wheels occur in several sizes and designs.

Known examples include:

Documented name	Part no.
Wheel 50mm Chrome	99126
Wheel 58mm Chrome	99127
Wheel Wide 92mm Chrome	99129
Wheel Narrow 100mm Chrome	99128

Chrome is a finish, not a single wheel size or construction type.

Some Chrome wheels are associated with themed K’NEX products, including vehicle-related sets. A particular Series or Theme should only be linked to a wheel when that relationship is documented; the theme does not replace the wheel’s physical classification.

Huge wheels

K’NEX also produced wheels substantially larger than the regular Small, Medium and Large Classic wheels.

Two documented Huge Orange versions are:

Documented name	Part no.
Wheel Huge Orange — hard tire	99031
Wheel Huge Orange — soft tire	99083

The distinction between hard and soft is important. These are materially different wheel/tire versions rather than simple color variants.

Monster Truck and 3-part wheels

Some K’NEX wheels use a more complex multi-part construction.

The Monster Truck / 3-part wheel system includes:

Documented name	Part no.
3-part wheel — Inner hub	99243
3-part wheel — Outer hub	99244
Monster Truck wheel	99242

These components form a wheel system rather than a conventional single hub with one simple tire.

The individual components are useful identification points when a complete Monster Truck wheel has been taken apart.

Motorcycle tires

K’NEX also produced distinctive colored Motorcycle tires.

Known colors include:

Documented name	Part no.
Tyre Motorcycle Blue	92140B
Tyre Motorcycle Green	92140C
Tyre Motorcycle Yellow	92140D
Tyre Motorcycle Red	92140E

These are visually and functionally distinct from the regular Standard, Racing and Narrow tire families.

Tires (Tyres) — quick reference

K’NEX used many different tire designs. Tire diameter alone is not sufficient to identify a part: width, tread, flexibility and compatible wheel center can also differ.

Known Classic tire types covered on this page include:

Type	Known part numbers
21 mm colored / special	99105B, 99105G, 99105R, 99105Y, 99105N, 99189, 99176
30 mm	531300
Standard Small	91975
Standard Medium	90976, 91976
Standard Large	91977
Large Plastic	3310029
Racing 37 mm	91150
Racing Slick 37 mm	91380
Racing 50 mm	91160
Narrow	91240
Motorcycle	92140B, 92140C, 92140D, 92140E

A tire should only be listed as compatible with a particular hub or wheel center where that combination is known or documented.

Hubs and pulleys

Some Classic K’NEX wheel centers are explicitly documented as Hub/Pulley parts.

Important examples are:

90978 family — Hub/Pulley Small — approximately 37 mm
90979 family — Hub/Pulley Medium — approximately 50 mm

A tire can turn these parts into wheel centers, but without a tire they can also function as pulleys.

Other K’NEX hubs may also be useful without a tire as hard wheels, rollers or rotating components.

This is why wheel, hub and pulley describe related but not always identical functions.

Wheel-related parts and accessories

Some K’NEX parts are closely associated with wheels without being wheels themselves.

One example is:

3310092 — K’NEX Sign

This part is known from a spare-wheel-related application in the Trail Rider. It remains classified as a Sign rather than as a Wheel.

Another wheel-related part is:

21841 — Skid plate / Eye center — Black

Its wheel-related application can be documented where the exact assembly is confirmed, but the part should not automatically be reclassified as a Wheel.

Other K’NEX parts used as wheels

K’NEX construction encourages parts to be used in more than one way.

A particularly clear example is the Classic 8-way connector. With a suitable tire fitted around it, it can form the center of a small wheel. The documented 43 mm Blue, Orange and Silver wheel combinations are examples of this principle.

Small 14-tooth Classic gears can also be used as simple wheels in suitable models.

These gears remain classified as Classic Gears. Their possible use as wheels is a building technique, not a reason to duplicate them in the Wheels family.

The same classification principle applies throughout K’NEXCHANGE:

what a part can do does not always determine what the part is.

Identifying an unknown K’NEX wheel

When identifying a loose K’NEX wheel, first check whether it consists of one part or several parts.

Useful identification features include:

outside diameter;
diameter and design of the plastic wheel center;
tire width;
tread pattern;
hard or flexible material;
open or closed center;
spokes;
narrow, wide or Racing construction;
color;
whether the wheel center is actually another K’NEX part, such as an 8-way connector.

Where possible, remove a detachable tire and identify the wheel center and tire separately. This can be much more reliable than identifying only the complete wheel.

About sizes

Wheel measurements require more care than rod measurements.

For rods, the nominal size describes the rod itself. For wheels, a published dimension may describe a hub, wheel center, tire or complete assembled wheel.

For example:

37 mm wheel center + Small tire → approximately 45–47 mm complete wheel

and:

50 mm wheel center + Medium tire → approximately 65 mm complete wheel

while a compatible 50 mm center with a Large tire can produce a wheel of approximately 90–92 mm.

For this reason, K’NEXCHANGE distinguishes between the size of the wheel center and the approximate outside diameter of the assembled wheel whenever the information is known.

About this overview

This page brings together known Classic K’NEX wheels, hubs, pulleys and tires and explains how the different wheel systems relate to each other.

Part numbers and documented names are compared with physical characteristics, known K’NEX parts lists and K’NEXCHANGE/AQ records. Because individual Ecwid items require unique identifiers, an AQ/Ecwid item number is not automatically treated as an original K’NEX part number.

Documented historical names are retained where useful, even when terminology or spelling differs from current K’NEXCHANGE usage.

Additional colors, historical part numbers and uncommon wheel combinations may exist. They can be added when they are reliably identified.

Last checked: August 24, 2026