What Measurements Do You Need When Looking for a New Castor?
When replacing or selecting a new castor, taking the correct measurements is essential to ensure a proper fit, safe operation, and direct compatibility with your existing equipment.
1. Wheel Size
Measure the overall diameter of the wheel (edge to edge through the centre) and the wheel width (tread width). This affects movement, load capacity, and equipment height.
2. Mounting Type
Identify how the castor is fixed to the equipment:
- Top plate (most common)
- Bolt hole / stem fitting
- Any special fittings or adapters
This ensures the castor will physically attach to your equipment correctly.
3. Top Plate Size (if applicable)
Measure the overall length and width of the plate. This confirms physical fit against the mounting surface.
4. Fixing Hole Centres (if applicable)
Measure the centre-to-centre distance between bolt holes in both directions, plus the hole diameter. This ensures the castor will line up with existing fixing points without modification.
5. Overall, Height
Measure from the ground to the top of the fixing plate or stem. This is important to maintain correct equipment height and clearance.
6. Bearing / Bore Type (if replacing like-for-like)
Identify the existing wheel bearing type:
- Plain bore (no bearing)
- Ball bearing
- Roller bearing
- Stainless steel bearing (for hygiene or corrosion resistance)
This affects ease of movement, load capacity, and durability.
7. Weight Capacity (Safe Working Load)
Confirm the maximum load requirement for your application and divide this across the number of castors being used.
Key considerations:
- Each castor has a maximum safe working load (SWL)
- Load should never exceed the rated capacity during normal use
- Allow for uneven surfaces where one or more castors may carry more weight than others
- Include a safety margin for dynamic movement (not just static load)
What Weight Capacity Is Needed When Selecting Castors and Wheels?
Weight capacity refers to the castor’s safe working load. Every castor and wheel has a maximum load rating that must not be exceeded during normal operation. You will need to calculate what weight capacity your application will need.
All Parnell castors and wheels specify a safe working load based on a travel speed of 3 km/h, providing a more realistic measure of performance in typical applications. Static load capacity is also listed in the product specifications. It is important to understand the difference between safe working load and static load capacity when comparing castors and wheels, as these ratings represent different operating conditions.
What Size Wheel Do I Need?
The diameter and width of a wheel can have a significant impact on how easily your castors and wheels move. Generally, the larger the wheel diameter, the easier it is to start, push, and roll—especially over uneven surfaces or obstacles.
However, wheel size is only one factor to consider. The load being carried, floor surface, operating environment, required manoeuvrability, and available mounting height will all influence the most suitable wheel size for your application.
As a general guide, larger diameter wheels provide lower rolling resistance and a smoother ride, while wider wheels help distribute weight evenly and reduce floor loading. Selecting the correct wheel size will improve performance, reduce operator effort, and extend the life of both the wheel and the castor.
How to Measure Wheel Diameter
To measure the correct wheel size, you need the overall diameter of the wheel, not the hub or fitting size.
- Place the wheel on a flat surface.
- Measure from the floor up to the highest point of the wheel (straight across the centre).
- Alternatively, measure straight across the wheel from edge to edge through the centre point.
- Ensure you are measuring the outside diameter of the tread, not the metal hub or axle.
Example:
- A wheel measuring 125 mm across is referred to as a 125 mm diameter wheel
Why It Matters
Accurate wheel sizing ensures:
- Correct fit within your equipment height restrictions
- Smooth and efficient movement
- Reduced operator effort
- Better performance over uneven floors and obstacles
- Longer service life of both wheel and castor assembly
What Size Top Plate / Fixing Hole Size Do I Need, and What’s the Difference?
1. Top Plate Size
This is the overall size of the metal plate that attaches the castor to your equipment.
Measure:
- Length of the plate (longest side)
- Width of the plate (shortest side)
Example: 140 mm × 110 mm top plate
This measurement helps identify the correct castor series, as larger castors typically have larger top plates.
2. Fixing Hole Centres (Bolt Hole Pattern)
This is the distance between the mounting holes.
Measure:
- Centre-to-centre distance between the holes along the length
- Centre-to-centre distance between the holes along the width
Example: Fixing centres: 105 mm × 80 mm
Also measure: hole diameter (e.g. 11 mm, 13 mm, etc.) to determine the required bolt size.
3. How to Measure
For a typical 4-hole rectangular top plate:
Measure:
- Overall plate length and width
- Distance from the centre of one hole to the centre of the opposite hole horizontally
- Distance from the centre of one hole to the centre of the opposite hole vertically
- Diameter of a fixing hole
Example Specification
- Top plate: 140 × 110 mm
- Fixing centres: 105 × 80 mm
- Hole diameter: 11 mm
Why the Difference Matters
- Top plate size determines whether the plate physically fits the mounting surface.
- Fixing hole centres determine whether the new castor will bolt directly onto your existing mounting holes without drilling new ones.
What Environment Will the Castors Be Used In?
The operating environment plays a major role in determining the right castor or wheel. Consider these three key factors:
Hygiene & Washdown Requirements
Food production, pharmaceutical, and clean-room environments often require stainless steel castors, sealed bearings, and non-marking wheels that can withstand frequent cleaning, chemicals, and moisture while preventing contamination.
Working Conditions & Exposure
Consider whether the castors will be exposed to water, chemicals, extreme temperatures, dust, debris, or outdoor conditions. Choosing materials suited to the environment helps prevent corrosion, wheel damage, and premature failure.
Industrial Demands & Floor Conditions
Heavy manufacturing and industrial settings may involve high loads, rough floors, impacts, and continuous use. Selecting castors designed for these conditions improves safety, reduces maintenance, and extends service life.
Why it matters: The right castor for your environment will last longer, perform more reliably, and help avoid costly downtime, replacements, and safety issues.
The style and material used to manufacture the castors and wheels makes them suitable for use in different conditions. However, some materials are more effective than others on given surfaces.
What Type of Surface Will the Castors Be Used On?
The floor surface has a significant impact on castor performance, manoeuvrability, and wheel life. Consider whether the castors will be used indoors or outdoors, and whether the surface is smooth, rough, hard, soft, dry, or wet.
Smooth vs Rough Surfaces
Hard wheels such as nylon and cast iron are best suited to smooth, even floors and offer low rolling resistance. For rough, uneven, or outdoor surfaces, softer wheels such as rubber or polyurethane provide better shock absorption and a smoother ride.
Floor Protection
If the floor surface is prone to marking or damage, softer wheel materials are recommended. Rubber and polyurethane wheels help protect delicate flooring while still providing good load-carrying performance. Polyurethane offers a higher load capacity than rubber while maintaining excellent floor protection.
Load & Durability Requirements
Heavier loads and more demanding environments require stronger castor constructions. Softer wheels can help absorb impacts and reduce vibration, protecting both the load and the equipment. For particularly heavy-duty applications, fabricated castors provide greater durability and load capacity than standard pressed steel castors.
Why it matters: Choosing the correct wheel material for your floor surface improves manoeuvrability, protects floors and equipment, reduces wear, and helps maximise the lifespan of your castors.
Is Noise a Concern in the Operating Environment?
The wheel material you choose can have a significant impact on noise levels during operation. This is particularly important in environments such as hospitals, schools, offices, retail spaces, hotels, laboratories, and residential buildings where excessive noise can be disruptive.
Wheel Material Affects Noise Levels
Soft wheel materials such as rubber and elastic rubber absorb vibrations and roll more quietly, making them ideal for noise-sensitive environments. Harder wheels such as nylon and cast iron tend to generate more noise, especially on hard floors.
Floor Surface Matters
Noise is often amplified when hard wheels are used on concrete, tiles, or other hard surfaces. Softer wheels help reduce vibration, minimise rattling, and provide smoother movement over uneven flooring.
Operator Comfort & User Experience
Quieter castors improve working conditions, reduce disturbance to staff, customers, patients, or residents, and create a more comfortable environment overall.
Why it matters: Selecting the right wheel material can significantly reduce noise, improve comfort, and ensure the equipment is suitable for environments where quiet operation is important.
Which Castor Mounting Type Do You Need?
Choosing the correct castor type is just as important as selecting the right wheel. The way the castor is mounted and whether it needs to swivel, remain fixed, or include a brake will affect manoeuvrability, stability, and safety.
Swivel or Fixed Castors
Swivel castors rotate 360° and provide maximum manoeuvrability, making them ideal for equipment that needs to change direction frequently. Fixed castors only move forwards and backwards, offering greater directional stability for straight-line travel.
Braked or Unbraked
If equipment needs to remain securely in place when stationary, a braked castor is recommended. The brake locks the wheel to help prevent unwanted movement, improving safety during loading, unloading, or operation.
Top Plate or Bolt Hole Fitting
Top plate castors are mounted using four fixing bolts and are the most common option for industrial and commercial equipment. Bolt hole castors use a single central fixing point and are often found on lighter-duty equipment, trolleys, and mobile furniture. Matching the fixing type to your existing equipment ensures a straightforward installation.
Why it matters: The right combination of swivel, fixed, braked, and mounting type will improve manoeuvrability, safety, and overall performance while ensuring the castors are suitable for your application.
Will the Castors Be Used in High or Low Temperatures?
Temperature can have a significant impact on castor performance, wheel life, and safety. Not all wheel materials are designed to operate in extreme heat or cold, so it is important to consider the environment before selecting a castor.
High-Temperature Applications
Environments such as bakeries, autoclaves, industrial ovens, and manufacturing plants can expose castors to elevated temperatures. Special heat-resistant wheels and bearings are often required to prevent wheel deformation, bearing failure, or reduced performance.
Low-Temperature & Freezer Environments
Cold stores, freezers, and refrigerated facilities can cause some wheel materials to harden, become brittle, or crack over time. Castors designed for low-temperature use maintain their performance and durability in these conditions.
Material Selection Matters
Different wheel materials have different operating temperature ranges. Choosing a wheel that is rated for your environment helps ensure reliable operation, longer service life, and reduced maintenance costs.
Why it matters: Using castors outside their recommended temperature range can lead to premature wear, wheel damage, and equipment downtime. Selecting the correct castor for the operating temperature will improve reliability, safety, and longevity.
Will the Castors Be Washed Down with Water and Chemicals?
If your castors are used in environments that require regular cleaning with water, detergents, or chemical disinfectants, material choice is critical to prevent corrosion, failure, and contamination.
Stainless Steel Castors for Washdown Environments
Stainless steel castors are the preferred option for wet and hygienic applications such as food production, pharmaceuticals, and medical settings. They are highly resistant to rust and corrosion, even with frequent exposure to water and cleaning chemicals.
Resistance to Cleaning Chemicals
In washdown areas, castors are often exposed to aggressive detergents, sanitising agents, and disinfectants. Stainless steel helps maintain structural integrity and appearance, reducing the risk of degradation compared to standard zinc-plated or mild steel castors.
Improved Hygiene and Longevity
Stainless steel castors are easier to clean and less likely to harbour bacteria or contaminants. This makes them ideal for environments where hygiene compliance is essential, while also significantly extending the service life of the castor.
Why it matters: Choosing stainless steel castors for washdown environments ensures reliability, prevents corrosion-related failure, and supports hygiene standards while reducing maintenance and replacement costs.
Do You Need Zinc, Stainless Steel, or Plastic Castors?
The bracket (frame) material of a castor is just as important as the wheel, especially when it comes to durability, corrosion resistance, and the working environment.
Zinc-Plated (Pressed Steel) Brackets
A cost-effective and commonly used option for general-purpose applications in dry, indoor environments. Suitable for light to medium-duty use where there is minimal exposure to moisture or chemicals. However, they are not ideal for washdown or corrosive environments as they can rust over time.
Stainless Steel Brackets
Best suited for food production, pharmaceutical, medical, and washdown environments. Stainless steel offers excellent corrosion resistance, even when exposed to water, chemicals, and frequent cleaning. It also supports higher hygiene standards and longer service life in demanding conditions.
Plastic Castors or Components
Typically used in light-duty applications where corrosion resistance and low weight are important. Plastic options can be useful in wet or chemical-prone environments but are not suitable for heavy loads or high-impact industrial use.
Why it matters: Choosing the correct bracket material ensures the castor can withstand its environment, maintain hygiene standards where required, and deliver safe, reliable performance over its lifetime.
What Tread Material Is Right for Your Application?
The tread material is one of the most important factors in castor performance, as it directly affects load capacity, floor protection, noise, and durability.
Hard Treads (Nylon, Cast Iron, Cast nylon)
Best for smooth, even floors and heavy loads where low rolling resistance is important. These materials are highly durable but can be noisy and may mark or damage delicate flooring.
Medium Treads (Polyurethane, Grey rubber)
A versatile option that combines strength with floor protection. Polyurethane offers higher load capacity than rubber, rolls smoothly, and is resistant to wear, oils, and many chemicals—making it ideal for industrial and commercial use.
Soft Treads (Black Rubber, Elastic Rubber)
Best suited for rough, uneven, or delicate floors. Soft treads absorb shock and vibration, reduce noise, and provide smoother movement, making them ideal for environments where comfort, protection, and quiet operation are important.
Why it matters: Selecting the correct tread material ensures better performance, protects floors and equipment, improves operator comfort, and extends the lifespan of the castor in your specific application.
Do You Need to Consider Anti-Static Castors (ELS / AS / EL)?
In some environments, static electricity build-up can create safety risks, damage sensitive equipment, or affect product quality. Anti-static castors are designed to safely dissipate static charge through the wheel and into the floor.
When Anti-Static Castors Are Required
Essential in environments where static discharge could be harmful, such as electronics manufacturing, laboratories, pharmaceutical production, and areas handling flammable materials or sensitive components.
Types of Anti-Static Options (ELS / AS / EL)
These ratings generally refer to different levels of electrostatic control and conductivity. They allow controlled dissipation of static electricity, helping prevent sudden discharge (sparks) and protecting both people and equipment.
Protection for Equipment, Product, and Safety
Anti-static castors reduce the risk of damage to electronic components, improve workplace safety, and help maintain product integrity in sensitive production environments.
Why it matters: If static build-up is not controlled, it can lead to equipment failure, safety hazards, or product defects. Choosing the correct anti-static castor ensures safe, reliable operation in sensitive environments.
Why It’s Important to Choose the Right Bore/Bearing Type
The bearing type (or bore type) has a major impact on how smoothly a castor performs, how much load it can handle, and how long it will last in service. It directly affects rolling resistance, ease of movement, maintenance requirements, and overall durability.
Plain Bore / No Bearing
A plain bore (also known as a plain axle or bush type) is the simplest wheel configuration, where the wheel runs directly on the axle or with a basic bush.
- Most economical option
- Suitable for light-duty applications and occasional use
- Higher rolling resistance compared to ball bearings
- Can wear faster under heavy loads or continuous use
- Can be a cheaper alternative to stainless steel bearings
Best suited for: light equipment, low-speed applications, and cost-sensitive projects.
Ball Bearing
Ball bearings use steel balls inside a race to reduce friction and allow smooth wheel rotation.
- Very smooth and easy to move
- Low rolling resistance, especially under load
- Suitable for higher speeds and frequent use
- Can be sealed for protection against dust and moisture
Best suited for: general industrial use, warehouses, retail, and applications requiring frequent movement.
Roller Bearing
Roller bearings use cylindrical rollers instead of balls, giving a larger contact area.
- Higher load capacity than standard ball bearings
- Excellent durability under heavy or shock loads
- Slightly higher rolling resistance than ball bearings
- Very robust in demanding industrial environments
Best suited for: heavy-duty industrial applications, rough floors, and high-load equipment.
Stainless Steel Bearings
Stainless steel bearings are designed for environments where corrosion resistance and hygiene are essential.
- Highly resistant to rust and corrosion
- Suitable for washdown, food, pharmaceutical, and medical environments
- Can be used in wet or chemically exposed conditions
- Often combined with sealed designs for improved hygiene and longevity
Best suited for: food production, pharmaceutical, clean rooms, marine environments, and washdown applications.
Why It Matters
Choosing the correct bearing type ensures:
- Easier movement and reduced operator effort
- Correct load handling and reduced risk of failure
- Longer service life and lower maintenance costs
- Better performance in specific environments (heavy-duty, hygienic, or general use)
- Improved safety and reliability of equipment
Using the wrong bearing type can lead to increased pushing force, premature wear, noise, corrosion, and unexpected downtime.
What is Shore Hardness?
Shore hardness is a measurement of how hard or soft a wheel material is, using a standard scale called the Shore A scale (for rubber and polyurethane wheels). It indicates how much a material resists indentation when pressure is applied.
In simple terms:
- Lower Shore rating = softer wheel
- Higher Shore rating = harder wheel
For example:
- Soft rubber wheels: approx. Shore A 70–80
- Polyurethane wheels: approx. Shore A 85–95
- Very hard materials (e.g. nylon): measured differently but behave as high-hardness wheels
How Shore Hardness Affects Performance
- Soft Wheels (Lower Shore Rating)
- Absorb shock and vibration
- Quieter operation
- Better grip on uneven or rough floors
- Improved floor protection
- Slightly higher rolling resistance
Best suited for: hospitals, offices, retail environments, and uneven surfaces.
2. Hard Wheels (Higher Shore Rating)
- Lower rolling resistance on smooth floors
- Higher load capacity in many cases
- More resistant to wear and abrasion
- Can be noisier and may mark some floor types
Best suited for: warehouses, industrial floors, and heavy-duty applications.
Why It Matters
Understanding Shore hardness helps ensure the correct balance between:
- Floor protection
- Noise reduction
- Ease of movement
- Load performance
- Wheel durability
Choosing the wrong hardness can lead to poor handling, increased noise, faster wear, or damage to floors and equipment.