Selecting the correct drive-wheel size involves more than measuring the outside diameter. Diameter, tread width, total width, hub length, bore, keyway, bearing seat and wheel offset all affect whether the wheel fits and performs correctly.
The correct dimensions must also match the equipment load, motor torque, travel speed, steering method and floor conditions. A wheel that fits the available space may still cause poor traction, excessive motor load or inaccurate vehicle movement.
This guide explains how to determine the correct size for industrial drive wheels used on forklifts, AGVs, pallet trucks and powered material-handling equipment.
Main dimensions to confirm:
Outside diameter
Tread width
Total wheel width
Hub length and offset
Bore diameter and tolerance
Keyway, spline or mounting-hole dimensions
Bearing or bushing dimensions
Required radial and axial runout
Why Drive-Wheel Size Matters
Drive-wheel size affects the complete drive system. Changing the diameter or width may alter vehicle speed, available torque, floor contact pressure, steering resistance and energy consumption.
For replacement projects, the original dimensions usually need to be maintained. For new OEM equipment, the wheel should be selected together with the motor, gearbox, chassis and intended route.
1. Outside Diameter
Outside diameter is the distance across the finished tread. It is usually the first dimension buyers provide, but it should not be treated as an isolated specification.
A larger drive wheel generally:
Passes over floor joints and small obstacles more easily
Produces more travel distance per wheel revolution
Requires more torque to produce the same force at the floor
May reduce the effect of small floor irregularities
Requires more installation space
A smaller drive wheel generally:
Fits more easily into compact drive units
Can produce greater force at the floor for the same axle torque
Rotates more times over the same travel distance
May be more affected by floor joints and debris
Changing wheel diameter on an existing vehicle can affect speed, ground clearance, encoder calibration and steering geometry. Replacement wheels should therefore match the original effective diameter unless the equipment design is being reviewed.
2. Tread Width
Tread width is the width of the polyurethane or rubber area in contact with the floor. It influences load distribution, contact pressure, heat dissipation and steering resistance.
A wider tread can spread the load across a larger contact area. However, excessive width may increase scrub and edge wear when an AGV or industrial vehicle turns by differential or skid steering.
The selected width should consider:
Maximum dynamic load per wheel
Available space inside the drive unit
Turning radius and steering method
Floor roughness
Polyurethane hardness and tread thickness
Operating speed and continuous runtime
3. Total Wheel Width and Hub Length
Total wheel width includes the tread and any projecting part of the metal hub. Hub length determines how the wheel sits on the shaft or inside the drive assembly.
Incorrect hub length can move the tread away from its intended centerline, causing misalignment, unequal loading or interference with nearby components.
Measure both the overall width and the position of the tread relative to the hub. A simple front-view photograph is not enough to confirm this geometry.
4. Bore Diameter and Tolerance
The bore connects the wheel core to the axle, motor shaft or drive hub. Its diameter and tolerance need to match the equipment design.
A bore that is too tight may prevent installation. A bore that is too loose can create movement, vibration, keyway wear and inaccurate rotation.
Provide:
Nominal bore diameter
Required tolerance
Shaft tolerance
Required fit type
Surface finish where specified
5. Keyway, Spline or Clamping Connection
Drive wheels require a reliable connection to transfer motor torque. Common connections include keyed bores, splines, clamping bushings, bolt patterns and flanges.
For a keyed bore, confirm:
Keyway width
Keyway depth
Keyway length
Position relative to the wheel centerline
Required corner radius or chamfer
The connection should be selected according to maximum torque, reversing frequency, available installation space and maintenance requirements.
6. Wheel Diameter and Motor Torque
Wheel radius affects the relationship between axle torque and the force produced at the floor. Increasing the radius without changing the motor or gearbox can reduce the available tractive force.
For new equipment, provide the motor torque, gearbox ratio, target speed, vehicle weight and ramp requirement. These values help determine whether the proposed wheel diameter is suitable.
For replacement equipment, avoid changing diameter simply to increase ground clearance. The effect on torque, speed and encoder calculations should be reviewed first.
7. Select Size According to Load
Drive-wheel load capacity cannot be determined by diameter alone. Tread width, material formulation, tread thickness, metal core, speed and duty cycle also affect the allowable load.
Start by calculating the maximum dynamic load carried by each wheel. Consider acceleration, braking, cornering, ramps and unequal weight distribution.
For high-load applications, read our guide to selecting polyurethane drive wheels for heavy loads .
8. Match the Size to Floor Conditions
Small-diameter wheels work best on smooth, clean floors. Rough concrete, expansion joints, thresholds and debris may require a larger diameter or a tread designed to resist impact.
Evaluate:
Floor material
Joint width and height
Thresholds or embedded tracks
Debris and surface damage
Ramps and transitions
Indoor or outdoor operation
A larger diameter may improve obstacle crossing, but the route should still be maintained where possible. Repeated impacts can shorten the life of the tread, bearings and drive unit.
9. Consider Steering Method
AGVs and mobile robots may steer through differential wheel speeds, rotating steering units or skid steering. The wheel diameter and tread width can influence turning resistance and side wear.
For precision vehicles, matching the effective diameter of the left and right drive wheels is also important. Diameter differences can cause tracking errors and unequal motor loading.
For automated warehouse vehicles, see our AGV and warehouse automation wheel solutions .
10. Check Manufacturing Tolerances
A drawing should define not only nominal dimensions but also the tolerances that affect installation and operation.
Important tolerances can include:
Outside diameter
Tread width
Bore diameter
Keyway dimensions
Radial runout
Axial runout
Concentricity between the tread and bore
Hub offset
Tighter tolerances may be required for AGVs, robots and high-precision motion systems than for low-speed manual equipment.
How to Measure an Existing Drive Wheel
| Dimension | Measurement Guidance |
|---|---|
| Outside diameter | Measure across the tread at several positions to check wear |
| Tread width | Measure only the polyurethane or rubber running surface |
| Total width | Measure the complete assembly including projecting hubs |
| Bore | Measure the finished internal diameter and identify the required fit |
| Keyway | Record width, depth, length and orientation |
| Hub offset | Measure the position of the tread relative to the mounting faces |
| Bearing | Record bearing code or inside, outside and width dimensions |
Measurement note: A heavily worn wheel may no longer show its original outside diameter. Where possible, provide the original drawing, equipment manual or an unworn sample.
Standard Size or Custom Drive Wheel?
A standard wheel is usually suitable when its dimensions, load capacity, material and mounting interface match the original equipment.
A custom drive wheel may be required when the equipment uses a special diameter, width, keyway, hub, tread profile or polyurethane formulation. Custom production may also be necessary when an original wheel is obsolete or when the existing design has repeated wear problems.
WSCS can review drawings, 3D models or physical samples for replacement and OEM projects. Send the wheel dimensions together with the equipment load, speed, floor and operating environment.
Frequently Asked Questions
Does a larger drive wheel carry more load?
Not automatically. Load capacity also depends on tread width, polyurethane formulation, tread thickness, metal core, speed and duty cycle.
Can I replace a drive wheel with a different diameter?
A different diameter may change vehicle speed, torque, ground clearance and encoder calibration. The drive system should be reviewed before making the change.
Which dimensions are needed for a replacement quotation?
Provide outside diameter, tread width, total width, hub length, bore, keyway, bearing dimensions and wheel offset.
Why must AGV drive wheels have matching diameters?
Different effective diameters can cause unequal travel per revolution, resulting in tracking errors and unequal motor loading.
Can WSCS manufacture a wheel from a sample?
Yes. A used sample can be reviewed, although an original drawing or unworn wheel is preferable when the existing tread has significant wear.
