There are several factors to consider when choosing wheels or castors for a trolley, piece of equipment or other application. Most castors consist of a wheel (or pair of wheels) fitted into a fork or frame. These components can be purchased together as a complete castor or separately, depending on your requirements.

You can browse our range of castors and wheels, or continue reading for some useful information to help you select the most suitable castor for your application. If you need more detailed or specific advice, contact us and we'll be happy to help.

Weight Rating

Each wheel and castor frame has a load rating indicating the maximum recommended weight it can carry.

For example, a wheel or castor rated to 50kg could be suitable for a trolley with four wheels where the combined weight of the trolley and its contents is less than 200kg, assuming the weight is distributed reasonably evenly and the trolley is used on a smooth surface.

If the trolley needs to travel over rough surfaces or is likely to be subjected to impacts, uneven loads or vigorous handling, we recommend choosing a wheel with a higher load rating to provide additional strength and durability.

For heavier applications, see our range of heavy-duty castors and industrial wheels.

Castor Height

Castor height is the measurement from the floor to the highest point of the castor. This determines how high the trolley or equipment will sit above the ground.

Castor height is particularly important when replacing an existing castor. If the new castor has a different load height from the original, the trolley or equipment may not sit level, which can result in an uneven or unbalanced load.

Swept Radius

The swept radius, sometimes referred to as the brake radius, is the distance from the centre of the swivel mechanism to the furthest outside point of the wheel or brake pedal, whichever extends further.

This measurement is important because it determines how far the castor will extend beyond the edge of the trolley or equipment as it swivels.

Clearance is especially important on equipment or furniture where the sides extend close to the floor. The castor needs enough room to swivel freely without hitting the frame or surrounding surfaces.

Wheel Material

The material used to manufacture a wheel has a significant effect on how it performs. Different materials are suited to different floors, loads and environments.

• Rubber: Generally provides the softest and smoothest ride, particularly over rough or uneven surfaces. Blue and grey rubber tyres are non-marking and are well suited to indoor applications.
• Polyurethane: Harder than rubber and well suited to smoother floors. Polyurethane wheels are non-marking, durable and generally require less effort to push than rubber wheels.
• Nylon: Easy to push on smooth surfaces and commonly used where low rolling resistance is required. However, dirt, stones and other debris can damage the wheel and potentially mark or scratch some flooring.
• Cast Iron: Designed for heavy-duty applications and environments where high temperatures or extreme loads are involved. Cast iron wheels can also be fitted with a polyurethane tyre where required.

See our range of castors to compare different wheel materials, sizes and load capacities.

Bearings

The type of bearing used in a wheel affects how easily the castor moves and the amount of effort required to push the trolley or equipment.

• Plain Bore: Requires the highest push effort but is generally the most economical option. Plain bore wheels are suitable for applications such as tables or equipment that only needs to be moved occasionally.
• Roller Bearings: Commonly used for heavier applications. Roller bearings can help distribute impact across the bearing surface and are particularly useful where wheels are subjected to heavier loads or rougher surfaces.
• Precision Ball Bearings: Provide smooth, low-effort rolling and are commonly used where easy movement and higher performance are important.

Wheel Size

The diameter of the wheel has a direct effect on how easily a trolley or piece of equipment can be pushed. Larger diameter wheels generally require less effort to push and perform better when travelling over uneven surfaces, thresholds and small obstacles.

Wheel diameter also affects the overall height of the trolley and the swept radius of a swivel castor. It is therefore important to consider available clearance as well as load requirements when choosing a wheel size.

Castor Frames

Castor frames are available in a wide range of designs and materials, including pressed steel, welded steel, zinc-coated, powder-coated and stainless steel options. Different frames are available for different load capacities and working environments.

Fixed castors are designed to travel in a straight line and are often combined with swivel castors when directional control is required.

For heavier loads, using swivel castors at the rear of a trolley can make manoeuvring easier and reduce the amount of twisting and strain required when changing direction.

Castor Brakes and Locks

Brakes and swivel locks are available on swivel castors and provide additional control when the trolley or equipment needs to remain stationary.

There are three common types:

• Total Brake: Locks both the wheel and the swivel mechanism, preventing the castor from rolling or swivelling.
• Wheel Brake: Locks the wheel while allowing the castor to continue swivelling.
• Directional Lock: Locks the swivel mechanism so the castor travels in a fixed direction while the wheel remains free to roll.

Browse our range of braked castors for applications where additional control is required.

Castor Fitting Options

Castors are generally attached to equipment using either a top plate or a single-bolt fitting. Choosing the correct fitting is essential, particularly when replacing existing castors.

Plate Mounted Castors

Plate-mounted castors have a flat plate on top with bolt holes for attaching the castor to a trolley, cabinet or other piece of equipment.

Plate sizes, shapes and bolt-hole patterns can vary between castors. When replacing an existing castor, it is advisable to check the existing mounting-hole dimensions so the new castor can be installed without drilling additional holes.

See our range of plate-mounted castors.

Single Bolt Mounted Castors

Single-bolt castors have a central hole at the top and are normally secured using a bolt or an expanding adaptor.

Expanding adaptors allow castors to be fitted into tubing and are available for round or square tubing in a range of sizes.

These fittings are commonly used on furniture, trolleys and equipment where a plate-mounted castor is not suitable.

Choosing the Right Castor

When selecting a castor, consider the total load, wheel size, floor surface, operating environment, required height, mounting method and how frequently the equipment will be moved.

There is no single castor that is suitable for every application. Choosing the right combination of wheel material, bearing, frame and fitting can make a significant difference to how easily and reliably your equipment moves.

Browse the full range of castors and wheels at SWC, or contact us if you need help selecting the most suitable castor for your application.