Do you find you’re always running out of storage space on your caravan holidays? Because towing a caravan automatically rules out hitching up a trailer for extended storage, making use of the roof of your tow car is a canny way to accommodate extra essentials. And whether you want to carry bikes or other sports gear up there, or you want to fit a roof box, you’ll need to start with a good pair of roof bars.

However, there’s a potentially bewildering choice out there. To help you understand what to look for so you buy the best, we’ve conducted a group test, so you can buy with confidence. All rail-mounted bars tested were ordered for a Volvo V70/850 Estate.

Carrying something on the roof of your car – with or without a caravan on tow – will hurt your fuel economy, so many roof bars are shaped to be aerodynamically efficient, which should also help fuel efficiency. This should also reduce the amount of wind noise, making journeys more peaceful.

You must be aware that different roof bars are designed and tested to support different maximum loads – you take care when packing your caravan and tow car, so do likewise when carrying things on your car’s roof. Think what you’re going to carry and what load limit you require from your roof bars. In addition, be sure that you do not exceed the lower of your vehicle’s maximum roof load weights (including the weight of the bars themselves), or the maximum load limit of the roof bars.

Our group test focused on rail-fit bars. And, where possible, we also considered the same bar fitted with mounts designed to be secured to door apertures, which can be rather more tricky to install and harder to fit on your own.

During our test, we assessed how easy the bars were to fit. Often, vehicle-specific products are far easier to fit than modular systems that are designed to be used on any car, however that also has its advantages.

What else should you consider if you’re looking to buy roof bars? Locks to help deter thieves are desirable, plus premium bars often feature T-tracks, narrow grooves cut into the top of the bars themselves that receive special bolts to secure your load.

Mont Blanc’s Supra range is for vehicles without roof rails, and versions are available to fasten into fixed points, door apertures, or even gutters. These are for door-aperture fitment, and installing them is typical of this type of mount: while fine-tuning the feet positions along the bar, it’s much easier if there’s a second person to hold the other end. A bonus, over similar-style products, is that the pinch bolts that lock the feet along the bar, laterally, are easily accessible from above. We also like the quality of the finish and the three-year warranty. But just over £100 is a lot to pay for basic bars with a limited 60kg maximum load, and no form of locks.

Our roof bars group test winner was the Thule WingBar, which retails for £150.50 and received a five-star rating.