Understanding Shore A Hardness for Floor Protection
Shore A is the standard measurement scale for soft elastomers — rubber and polyurethane. A lower number means a softer, more deformable material. For floor protection, softer is generally better because a softer wheel spreads its contact area over more floor surface, reducing the pressure per square inch that causes scratching and indentation.
- →Shore A 60–75: Very soft PU or rubber. Maximum floor protection. Noticeable rolling resistance, especially on carpet. Best for premium stone lobbies with lighter loads.
- →Shore A 75–85: Soft to medium PU. Best all-around for marble, travertine, hardwood, and porcelain. Good floor protection with manageable rolling resistance.
- →Shore A 85–95: Medium to hard PU. Better for LVP, carpet, and mixed surfaces. Reduced floor protection on premium stone — not recommended for polished marble.
- →Shore D 50+: Hard polyurethane, nylon. Low floor protection on finished surfaces. Appropriate for industrial and back-of-house areas only.
Wheel Diameter and Load Distribution
Wheel diameter affects floor protection through two mechanisms. First, a larger diameter wheel has a larger contact patch with the floor — the load is spread over more surface area, reducing pressure per square inch. Second, larger wheels roll more easily over transitions (carpet-to-tile thresholds, elevator sills), reducing the impact load that occurs when a small wheel drops into a floor gap.
For lobby and premium floor applications, 4"–6" diameter wheels are the right range. Anything smaller than 3" should not be used on high-value flooring under significant loads. For very heavy equipment (staging platforms, large A/V rigs), combine the largest practical wheel diameter with the softest practical tread to distribute load as widely as possible.
The Cost of Getting It Wrong
Marble restoration and polishing: $8–$25 per square foot. Luxury vinyl plank replacement in a hotel corridor: $4–$12 per square foot plus labor and room downtime. Hardwood refinishing: $3–$8 per square foot. These costs should be framed against the cost of the correct caster specification — typically $20–$80 per caster — and the cost of a preventive caster replacement program.
Properties that spec correctly on initial cart purchases and replace casters on a defined maintenance schedule (annually for high-use carts, every 18–24 months for moderate-use) effectively eliminate floor damage as a caster-related maintenance expense.