What wheel size does a Wheeled Protective Case need?

A: Size for the worst ground of the year: 50–75 mm indoors, 100 mm on plant concrete, 125 mm on gravel, 160 mm for steps.

Can a Wheeled Protective Case fly?

A: Most carriers cap checked baggage near 158 cm total, so removable wheels help.

A: Four for flat pushing and heavy loads, two for narrow aisles and light loads.

How much handle play is normal?

A: Under three millimetres fore and aft when fully extended. Beyond five, towing feels vague and the tube is too thin.

Does a 50 kg rating mean 50 kg of contents?

A: No. The figure is static; towing puts everything on two wheels, so keep contents near sixty percent of the rating. ---

How to Choose a Wheeled Protective Case: Wheels, Handle, Load

Quick answer: Fix the wheel diameter first, then the handle, then the load rating. Size wheels for the worst ground you will meet, not the best; check grip height and sideways play under three millimetres; rate wheels for two-wheel towing, not four-wheel static load.

Four parameters of a Wheeled Protective Case
Wheel diameter and tread: read the ground first
Handle: stages, locking and grip height
Load: weight, contents and impact together
Acceptance and three common mismatches
FAQ

1. Four parameters of a Wheeled Protective Case

A Wheeled Protective Case has four parameters: wheel diameter, tread, handle and load rating. They are sequential, not parallel. Diameter sets what ground the case can cross, tread sets whether it grips there, the handle sets towing effort, and the rating decides whether the first three hold.

Wheeled Protective Case: rear of a black case, moulded top handle across the width, two hinges stacked on the side face, even matte texture

A case rated at fifty kilograms on fifty millimetre wheels stops dead in gravel: small wheels shorten the lever arm.

2. Wheel diameter and tread: read the ground first

Wheeled Protective Case: silver-grey case standing upright on four black castors, recessed top handle, vertical ribs down both corners

Clearance runs at about forty percent of diameter: 20 mm at 50 mm, 40 mm at 100 mm, 65 mm at 160 mm.

Diameter	Clearance	Ground	Typical fit
50 mm	20 mm	indoor tile	light instrument case
75 mm	30 mm	airport tile, epoxy	cabin-style case
100 mm	40 mm	plant concrete	general equipment
125 mm	50 mm	gravel, grass	field work
160 mm	65 mm	steps, sites, sand	cart-style

Tread is the neglected half: polyurethane wears slowly and runs near 62 dB on tile, nylon is harder but loud, rubber grips best and wears fastest. On gravel, take a tread at least 40 mm wide or the case ploughs. Polyurethane also stiffens below minus twenty.

3. Handle: stages, locking and grip height

Wheeled Protective Case: case lying on asphalt, scuffed lid, two latches and a folding handle on the front, open hangar and a jet behind

The first handle number is extended height, not stage count: the grip sits near half the user's height, about 850 mm at 1.7 m.

Type	Extended height	Wall	Play allowed
Two-stage	900–1000 mm	1.2–1.5 mm	≤3 mm
Three-stage	1050–1100 mm	1.2 mm	≤4 mm
Fixed	case height	1.5 mm	≤1 mm

Play is the quickest test: extend fully, push fore and aft, and beyond three millimetres the case sways as you walk. It comes from thin walls, a worn pin or an undersized mounting plate. Buttons work one-handed but resist gloves; levers clear thick gloves.

4. Load: weight, contents and impact together

Wheeled Protective Case: black case on a hangar apron, four latches across the front, two folding handles at the sides, small casters at the lower corner

Load ratings promise more than the case can keep. Four wheels share weight only when the case stands upright; tilt it to tow and two wheels carry everything.

Item	Example	Note
Case weight	8.5 kg	wheels and handle included
Contents	25 kg	actual load
Total	33.5 kg	sum of the two
Towing, two wheels	16.8 kg each	total divided by two
Wheel rating	≥25 kg each	towing figure × 1.5

Impact adds on top: kerbs and drops peak near three times static load, and an 8 mm axle goes oval within six months. Without ribs under the base, a heavy load bows the floor and four wheels become two.

5. Acceptance and three common mismatches

Three checks take under a minute: push five metres straight for drift, spin the case for free rotation, extend the handle and rock it for knock.

The first mismatch is a large case on small wheels that cannot cross the plant's speed humps. The second is a heavy case on two, where the tilted tow loads one wrist. The third is a long handle on a thin wall.

Conclusion

Choosing a Wheeled Protective Case comes down to one line: diameter follows the ground, handle follows the user's height, rating follows the towing attitude. Leave the margin on diameter, because it governs clearance, noise and life, and cannot be changed after delivery.

This article covers container-side specifications and design implications only, not the handling, loading or use of the contents.