Best roof boxes for three different carrying needs

Which one would make your journeys easier?

For a large amount of bulky luggage, the Motion 3 XL is the spacious choice in this shortlist. Its product page gives an interior of 203 × 74 × 37cm; the fitting manual gives a smaller 202.4 × 73.6 × 35cm. Use the smaller dimensions for initial packing checks and confirm the supplied unit. The large shell gives you room to organise luggage, but its planning weight of at least 23.2kg is a reason to calculate first: a low roof allowance may leave you with more volume than usable payload.

The Force 3 L Sport makes more sense when width matters. It is narrower than the Motion 3 XL, though its 51cm published internal width makes wide suitcases less convenient. A narrow box can be a starting point for carrying a bike alongside, but the bike carrier, clamps and box opening still need enough usable bar width. Do not buy the box on the assumption that every shared roof layout will work.

The VonHaus 320L is the compact option for occasional luggage. Its 132cm-long shell is much shorter than the two Thule models, and its 11.5kg empty weight leaves more of the same vehicle allowance available. The trade-off is a shorter interior and single-side opening. It is not a substitute for a long ski box, and you still need the mounting requirements confirmed for your bars.

For a more specific choice, compare narrow roof boxes, low-profile shapes or lighter options. Our size guide helps you establish the load before selecting a model.

If you are choosing between the Thule ranges rather than these contrasting shapes, use the Force 3 versus Motion 3 comparison in equivalent sizes. The L Sport and XL shown here answer different carrying needs, so their capacity difference alone is not a verdict on either range.

If a rigid shell is difficult to store, compare a roof box with a roof bag and check the actual support and attachment permissions. An alternative format still needs the complete vehicle and load checks.

Manufacturer figures that need checking

Thule's UK product page lists 14.8kg, while the currently linked Force 3 manual lists 15.4kg for L Sport. Use at least 15.4kg when planning the empty-box allowance, and confirm the figure for the supplied unit with Thule. Weighing the actual box and installed rack avoids relying on rounded figures when your remaining allowance is tight.

Motion 3 XL also differs: its product page lists 23kg, while the linked manual lists 23.2kg and a smaller usable interior. Plan with at least 23.2kg and the smaller internal dimensions stated above. Confirm the actual unit before relying on a close fit.

The Force manual also gives more precise shell dimensions than the rounded product-page values. Use the installation drawing for clearance decisions and measure the installed setup. A catalogue dimension is a way to shortlist; it is not a clearance guarantee.

Litres tell only part of the story

Lay out the luggage you expect to carry, then measure the largest packed items. The limiting dimension may be the height of a suitcase beneath a tapered lid rather than total volume. Box mounts and straps occupy space too.

The VonHaus interior is published as 122 × 69 × 33.5cm. The Force 3 L Sport interior is 183 × 51 × 36.5cm on its product page. Those shapes do different jobs: a short, broad bag may suit the former, while a long bag may need the latter. Neither should be chosen simply because the volume starts with a three.

Avoid assuming a nominal litres-per-person rule. Two households can carry very different kit for the same number of travellers. Check your own luggage, especially tent bags, rigid cases and long sports equipment.

Empty weight changes what you can pack

Consider an illustrative car with a 75kg total roof limit and a 5kg complete rack. Allowing 23.2kg for a Motion 3 XL leaves 46.8kg for luggage before allowing for any other roof equipment. That is 75 − 5 − 23.2, not the box's advertised 75kg luggage limit. The rack's own capacity could reduce it further.

Using 15.4kg for the Force 3 L Sport gives 54.6kg on the same illustrative setup. The VonHaus leaves 58.5kg under the vehicle calculation, but its own 55kg luggage limit reduces the allowance to 55kg before any lower rack limit. These figures describe an example, not your car.

Use the load calculator with verified figures for your vehicle and full rack. Include other carriers and their loads, even if their luggage never goes inside the box.

Compare the shortlist under the same roof allowance

What opening and mounting features actually change

Two-sided opening on the Thule boxes lets you work from either side of the vehicle. That helps when the convenient side changes between your driveway and a destination car park. With a single-side box, think about access to the opening and mounting points in the places you normally load.

PowerClick gives a tightening indication on the named Thule boxes. It does not replace checking the approved crossbar profile, clamp clearance or spacing. Read the complete instructions; an apparently secure clamp is not sufficient evidence of compatibility.

A lock helps keep the lid closed as designed, but it is not a reason to leave valuables unattended. Do not overfill the box or force a reluctant lid or lock. Repack and check the closing instructions.

The four measurements to collect before ordering

1. Your luggage: packed length, width and height, compared with the interior and opening.
2. Your bars: profile dimensions, permitted spacing and usable loading width, checked against the box instructions.
3. Hatch clearance: measured using the exact model's method, followed by a check of the actual opening path.
4. Off-car storage: the shell's footprint and the space needed to move and support it at home.

Thule specifies front-clearance measurements greater than 1,265mm for the Force 3 L Sport and 1,324mm for the Motion 3 XL, using its front-crossbar-to-hatch method. Only use these for those exact variants. A bar position may be fixed by the vehicle-specific kit; do not move it simply to make a box clear.

The VonHaus product page does not supply a model-specific hatch-clearance figure or the full installation dimensions for matching bars. Ask VonHaus for the supplied model's instructions and confirm clamp and spacing compatibility before purchasing. A short shell does not remove that check.

When to choose a different setup

If the weight calculation leaves too little luggage allowance, a bigger box will not solve it. Reduce the roof load, compare a lighter approved box, or consider another vehicle-approved carrying method.

If a box would be used for one short trip and you cannot store it, compare hire or a suitable foldable carrying system. For a roof bag, verify the attachment method and vehicle restrictions separately. It is not automatically a safe alternative on a naked or glass roof.

A full-width box can also be the wrong choice when you need to carry bikes or boards alongside. Check the mixed-load considerations before buying two accessories independently.

Questions worth settling now

Specifications and fitting sources

Box specifications and accessory listing checked October 2026. Confirm the instructions for the actual unit and vehicle before fitting; manufacturer documents and retailer variants can change.