When caster wheels "deform, crack or the bearings fail" sooner than they should, it is usually not because the wheels are bad, but because the wrong load rating was chosen in the first place. This article summarises how engineers actually calculate load per wheel, so you choose wheels that last and give good value.
Load-per-Wheel Formula
The key principle is "don't divide by 4" even though the cart has 4 wheels. In reality factory floors are never perfectly flat, and at times only 3 wheels carry the load together, so allow for it.
Load per wheel = (cart weight + maximum load) ÷ 3
Choose a wheel rated ≥ this value × 1.5–2 (safety factor)
Choose a wheel rated ≥ this value × 1.5–2 (safety factor)
Worked Example
Suppose the cart weighs 50 kg and carries up to 600 kg, a total of 650 kg.
- 650 ÷ 3 = 217 kg per wheel
- With a ×1.5 safety factor = 325 kg per wheel
- Choose a wheel rated ≥ 325 kg each → choose the 6-inch model (350 kg each)
Why allow a margin: impacts when rolling over gaps, dropping off edges or starting off make the momentary load spike to several times the static load. A 1.5–2× margin keeps wheels from failing prematurely.
Basic Size Selection Table
| Total weight / cart | Load per wheel (÷3) | Recommended |
|---|---|---|
| Up to 750 kg | ~250 kg | 4 inch (250 kg each) |
| 750–1,050 kg | ~350 kg | 6 inch (350 kg each) |
| Over 1,050 kg | Over 350 kg | Multiple 6-inch casters |
The values above already include some safety factor. If the work involves frequent impacts or all-day pushing, we recommend moving up to a higher-rated model.
Don't Forget Factors Other Than Weight
- Steel core: a thick cast core (e.g. 5.5 mm) keeps the wheel from deforming under full load
- Bearings: double bearings keep pushing smooth, without drag, even with heavy loads
- Floor surface: epoxy floors should use PU so wheels don't leave marks or scratch the floor