X-BULL Waterproof Car Roof Cargo Bag 595L Top Rack Carrier Luggage Storage Cube

595 litres is about the boot of a large wagon, lifted onto the roof. That is the capacity X-BULL publishes for this cargo bag, and it is the whole reason for owning one: swags, chairs and the kids' bags go up top, and the back seat stops being a storage cupboard for the entire drive.

Packing the awkward things

Soft luggage is what suits a bag like this - bedding, clothing, camp chairs, anything that presses into a corner. A single large zip opening loads more like an oversized duffel than a hard pod, and at home the whole thing folds down to nearly nothing, which is the trade against a moulded box that needs garage space year round. Note that 595 L is a volume figure. What you can actually carry up there is set by the vehicle and the rack, never by the bag.

Three layers of 900D PVC

The shell is three-layer 900D PVC, the same family of coated fabric used for truck tarps: heavy, stiff and awkward to tear. X-BULL says it protects luggage from wind, sand, rain, snow and sunlight. Sand is the real test on a corrugated road, and coated fabric wipes clean rather than trapping grit in a weave. The supplier calls both the fabric and the zip waterproof; treat the bag as water-resistant in service and line anything that must arrive dry.

Key features

• 595 L stated capacity: frees up the cabin on a long trip with a full car.
• Coated three-layer shell: 900D PVC that wipes down after a gravel road.
• Covered zip: supplier measures the widened cover at 4.7 in.
• Folds flat: lives in a cupboard between trips rather than filling the garage.

Specifications

• Capacity: 595 L, supplier-stated
• Material: three-layer 900D PVC
• Closure: zip beneath a widened cover, supplier states 4.7 in
• Restraint: reinforced adjustable straps; the supplier does not publish how many, or how they anchor
• Anti-skid pads: included
• External dimensions: not published
• Water resistance: described by the supplier as waterproof, including the zip; no standard or test is named
• Load rating: none published for the bag or its contents

Before you load the roof

• Your ceiling is whichever is lower: the roof load limit in the vehicle handbook, or the rack's own rated capacity. The rack and the empty bag both count against it.
• Loaded, the bag adds height to the vehicle. Measure it before a drive-through, a boom gate or an undercover car park.
• Check the straps after the first half hour, then at every stop - soft loads settle and slacken as they compress.
• Keep the pads between the bag and any painted surface.

A sensible answer for one or two big trips a year, when a hard box is more storage problem than it is worth.