Selecting the right wheels or castors for a trolley, mobile equipment, or industrial framework involves balancing load capacities, surface types, and mounting configurations. Most castors consist of a wheel (or pair of wheels) housed inside a fork or frame. These can be purchased as complete units or individual components depending on your setup.

Browse our complete range of castors and wheels, or use the guide below to determine the exact specification for your environment. Need tailored assistance? Contact the SWC team for expert technical advice.

1. Weight Rating & Load Capacity

Every wheel and castor frame carries a specified maximum load rating. As a general rule, calculate total weight by combining the tare weight of the trolley with the maximum intended payload.

For example, a castor rated to 50 kg could theoretically support a 200 kg total payload across four wheels on a perfectly smooth surface. However, real-world conditions require safety margins:

• Rough surfaces & obstacles: Bumps, thresholds, and expansion joints temporarily transfer the entire load onto only three—or even two—wheels.
• Shock loading: Dropping heavy items onto a trolley dramatically increases instant forces on the castor rig.
• Recommendation: Always select a load capacity higher than your minimum mathematical requirement to account for uneven surfaces and handling impact.

For heavy industrial environments, explore our dedicated range of heavy-duty castors.

2. Castor Height & Overall Clearance

Castor height (or overall height) measures the total distance from the floor surface to the top of the mounting plate or stem. This dictates the working clearance of your equipment.

When replacing a single damaged castor, matching the exact load height of the existing units is critical. Uneven castor heights lead to unstable, wobbly equipment and premature wear on the longer castor.

3. Swept Radius & Swivel Clearance

The swept radius (or brake radius) measures the distance from the vertical axis of the swivel mechanism to the extreme outer edge of the wheel or brake pedal.

This measurement determines the clearance envelope required for the castor to complete a full 360° swivel without colliding with the trolley chassis, surrounding skirt, or adjacent equipment.

4. Wheel Material Selection

Wheel tread material dictates rolling resistance, noise levels, and floor protection:

• Rubber: Delivers maximum shock absorption and quiet operation over rough ground. Non-marking blue and grey rubber tyres are ideal for indoor commercial floors.
• Polyurethane: Harder and more durable than rubber, offering low rolling resistance on smooth concrete floors while remaining non-marking and chemical-resistant.
• Nylon: High load capacity and extremely easy to push on smooth surfaces. However, hard nylon can track debris and potentially score soft floor coatings.
• Cast Iron: Engineered for extreme loads, high heat, and harsh industrial environments. Available plain or fitted with a polyurethane tyre for noise reduction.

5. Bearing Types & Rolling Effort

The internal bearing mechanism governs how easily the equipment starts rolling and stays in motion:

• Plain Bore: Simple, economical, and maintenance-free. Best suited for short-distance equipment or stationary units moved only occasionally.
• Roller Bearings: Heavy-duty cylindrical rollers that distribute impact effectively across the axle. Ideal for manually pushed trolleys carrying heavier payloads.
• Precision Ball Bearings: Sealed bearings providing the lowest rolling resistance and smoothest operation. The top choice for high-frequency or ergonomic applications.

6. Wheel Diameter

Larger diameter wheels roll over bumps, floor joins, and debris much easier than small wheels. If push effort and operator ergonomics are primary concerns, opt for the largest wheel diameter your frame clearance permits.

7. Castor Frames & Swivel Dynamics

Castor frames are available in pressed steel, heavy welded steel, stainless steel, and zinc-plated finishes for corrosion resistance.

• Fixed Castors: Constrained to travel in a straight line. Combine two fixed castors at the rear with two swivel castors at the front for precise steering control.
• Swivel Castors: Rotate 360° to allow omnidirectional movement in tight spaces. Placing swivel castors at the pushing end reduces physical strain during directional changes.

8. Brakes and Swivel Locks

Locking mechanisms secure equipment safely on slopes or during loading:

• Total Brake: Simultaneously locks both the wheel rotation and the swivel head, locking the castor completely rigid.
• Wheel Brake: Locks wheel rotation only while allowing the top frame to swivel freely.
• Directional Lock: Converts a swivel castor into a fixed castor on demand, aiding straight-line tracking over long distances.

View our selection of braked castors for static stability.

9. Mounting Options: Plate vs. Stem

Selecting the correct attachment fitting ensures rigid mounting without structural damage:

Plate-Mounted Castors

Features a flat mounting plate with four bolt holes. When replacing plate mounted castors, measure the bolt hole centers (pitch) to ensure direct alignment without re-drilling the frame base.

Single-Bolt & Stem-Mounted Castors

Secured via a single central bolt hole or expanding stem adaptor. Expanding adaptors fit tightly inside round or square tubular legs, making them ideal for light-to-medium duty furniture and catering trolleys.

Summary: Choosing the Right Castor

To select the ideal castor, evaluate four primary factors: total load weight, floor surface condition, operating environment, and mounting geometry. Choosing the correct combination of wheel material, bearing type, and frame style will maximize equipment lifespan and ease of use.

Explore the complete range of industrial castors and wheels at SWC, or get in touch with our Auckland specialists for custom recommendations.