How to Choose the Hardness of Polyurethane Casters?

Polyurethane Caster Hardness Selection Guide
The hardness of polyurethane (PU) casters is a key parameter affecting their performance, directly impacting load capacity, wear resistance, shock absorption, and effort-saving propulsion. Selection requires a comprehensive assessment based on the application scenario, load requirements, floor conditions, and equipment characteristics. The following is a detailed analysis:

 

Polyurethane Hardness Specification and Key Impacts
The hardness of polyurethane casters is typically expressed in Shore Hardness, with the mainstream range being 60A to 95A (50A or 98A is permitted in a few specialized scenarios). Higher hardness indicates a more rigid character; lower hardness indicates a more flexible character:

 

Low hardness (60A to 75A): Offers good elasticity, strong shock absorption, and low noise, but also offers lower load capacity and average wear resistance.

 

Medium hardness (75A to 85A): Balances elasticity and wear resistance, provides moderate load capacity, and offers the widest range of applications.

High hardness (85A-95A): Strong rigidity, high load-bearing capacity, and excellent wear resistance, but also poor shock absorption and high noise.

 

Application Scenarios and Selection Criteria for Different Hardness Types
1. Low Hardness (60A-75A): Emphasizes shock absorption and quiet operation
Core Advantages

 

Excellent elasticity absorbs floor bumps and protects delicate equipment components (such as instruments and electronic equipment);
Large contact area with the floor and excellent slip resistance, preventing slipping on smooth surfaces (such as tile and marble);
Low rolling noise (≤60 decibels), suitable for noise-sensitive environments.

 

Applicable Applications
Light-load equipment: Medical equipment carts, laboratory equipment wheels, and mobile bases for precision instruments (single wheel load ≤100kg);
Smooth floors: Indoor and outdoor tile, epoxy, and marble floors to avoid scratches caused by excessive hardness;
Vibration reduction requirements: Audio equipment and photographic equipment carts to reduce the impact of vibration on internal components.

 

Precautions

Low wear resistance: Avoid prolonged use on rough surfaces (gravel, concrete), as this can easily cause wheel wear or tear.

Limited load capacity: Overloading can easily cause wheel deformation, overheating, and aging.

 

2. Medium Hardness (75A-85A): General-Purpose Type

Core Advantages

 

Balance of elasticity and rigidity: Provides a certain degree of shock absorption (reducing equipment vibration) while maintaining load capacity (100-300kg per wheel).

 

Balanced wear resistance: When rolling on moderately rough surfaces such as concrete and asphalt, wear is slowed, resulting in a longer service life.

 

Moderate pushing resistance: Reduces effort compared to low hardness and improves steering control compared to high hardness.

Applicable Applications

 

Medium-load general-purpose equipment: Logistics carts, tool carts, supermarket shopping carts, and outdoor cleaning vehicles.

 

Mixed Surface Environments: Alternating between indoor concrete and outdoor asphalt surfaces, or where the surface has slight gravel or joints.

 

Combined Applications: Applications requiring both shock absorption (to protect cargo) and frequent movement (saving effort) and durability. Precautions

 

Use caution when selecting for extremely heavy loads (>300kg/wheel) or extremely rough surfaces (such as gravel roads at construction sites), as localized wear of the wheel tread may accelerate.

 

3. High Hardness (85A-95A): Emphasizes load-bearing and wear resistance
Core Advantages

 

High load-bearing capacity: A single wheel can carry loads of 300-1000kg, suitable for heavy equipment;

 

Excellent wear resistance: The wheel tread has a high hardness and excellent tear and puncture resistance, making it durable even under rough surfaces such as gravel, concrete, and steel plates.
Stable structure: Resists softening in high temperatures (≤80°C) and brittleness in low temperatures (≥-30°C), making it suitable for complex outdoor conditions.

 

Applicable Applications
Heavy-load equipment: Industrial forklift auxiliary wheels, heavy-duty racking wheels, and support wheels for construction equipment;
Harsh surfaces: Construction sites, mines, outdoor gravel roads, and rough surfaces, or where sharp objects (such as nails and glass) are present;
High-frequency use: Equipment that requires long periods of frequent rolling, such as pallet trucks in logistics warehouses and container trailers at ports.

 

Notes:
Poor shock absorption easily transmits ground vibrations to equipment, making it unsuitable for precision instruments or fragile cargo.
Noisy (≥75 decibels), slightly higher rolling resistance, and requires more force to push.

 

Key Factors for Choosing Hardness
Load Size
Single-wheel load <100kg: 60A-75A preferred (lightweight + shock absorption);
Single-wheel load 100kg ≤ ≤ 300kg: 75A-85A preferred (general balanced);
Single-wheel load >300kg: 85A-95A required (high load-bearing strength).

 

Surface Roughness
Smooth surfaces (cement, epoxy): Low hardness (protects the surface and prevents slipping);
Medium-rough surfaces (cement, asphalt): Medium hardness (balanced wear resistance and shock absorption);
Extremely rough surfaces (sand and gravel, construction sites): High hardness (wear and puncture resistance). Equipment Characteristics
Precision/Fragile Equipment: Low Hardness (Shock Absorption and Damage Prevention);
Heavy Duty/Industrial Equipment: High Hardness (Load-Bearing and Wear-Resistant);
General Mobile Equipment: Medium Hardness (Overall Cost-Effectiveness).

 

Frequency of Use and Ambient Temperature
For frequent use or high-temperature environments: Choose a high hardness (Aging and Deformation Resistance);
For low-temperature environments (<-10°C): Avoid low hardness (Easy to Brittle); 80A or higher is recommended;
For occasional use or ambient temperature environments: Either medium or low hardness is acceptable, prioritizing comfort.

 

Additional Recommendations for Special Scenarios
For quiet operation and moderate loads: Choose a "soft, high-elastic polyurethane" with a 75A-80A rating, which offers increased elasticity in addition to hardness.

 

For outdoor use in rain and snow: Regardless of hardness, choose a polyurethane with a waterproof formula to prevent performance degradation after water absorption.

 

For Customized Needs: Some manufacturers offer mixed-hardness wheels (high hardness core + low hardness tread) to balance load bearing and shock absorption. In short, when choosing the hardness of polyurethane casters, we should avoid "blindly choosing high hardness" or "only looking at the price". We should find the balance point of "load bearing, wear resistance, shock absorption, and labor saving" based on the actual working conditions to maximize the service life and usage experience of the casters.