How to Fit a Roof Box on Car? Everything You Need To Know

If you want to go on a trip with your friends or family and want to enjoy a comfortable ride, a roof box is a solution to enjoy the ride with full of comfort by keeping the items in the roof box and not in the passenger seats.

You have to make sure that your roof box is properly and safely attached to your car. But how can you do that?

Here, you will find the way to Fit a roof box on a car quickly, easily, and safely.

Do You Need Roof Bars for a Roof Box?

Roof Bars

Yes, of course. Roof bars are very important for installing a roof box. You cannot do that with the help of a rope. You have to find a place for the box to bolt into on top of your car or van.

Suppose your car does not match the standard size of the roof bars. You can then order a set and have them installed so that you can safely install your roof box.

Installing a roof cargo box on top of your car is the easiest way to increase your car’s storage capacity. But you have to install them correctly. If they are installed incorrectly, then they can be harmful to your car.

Installing a roof box is not a hard task. But you have to keep some important matters in your mind before installing the box, such as the weight capacity of the roof of your car or the roof bars weight capacity.

Do Some Research

Before buying a roof box or a set of roof bars, you should always do some research. It would be best if you did not go for the cheapest roof bar options available on the market. Moreover, you should also choose bars that are compatible with the roof of your car and the roof box you want to buy unless you will not be able to use them for a long time.

Can a Roof Box Overhang?

Roof Box Overhang

There can be some overhang when a roof box is installed on a car, but you should keep it to a minimum amount. Finding the 100% perfect size of the roof cargo box can be difficult, so buying a roof box that is an inch or two inches bigger than the exact size is OK and will not cause you any problem.

But if you choose a roof box bigger than a couple of inches on each side, it can create some problems, including balance issues. So you will not be able to enjoy a clean and quiet ride. A jerky ride is not comfortable at all, and it is very dangerous.

But still, if you can’t avoid the overhang, you should find a longer, not wider, roof rack. You should find the roof bars that are designed to accommodate longer stuff so that more support can be added to the roof box.

It would be best to choose a roof box that will not interfere with any other road users. So you should not install a roof box designed for an Audi Q7 on a Mini Cooper.

You should not accept too much overlap at the back because if you are driving a hatchback or a car with a trunk door that lifts higher than normal, the trunk can get damaged with the roof box.

There is also a possibility of smashing your rearview window, which is not a good thing. So choose the box which is not too much overlap.

A Balancing Act

After all, it would be best if you also were careful about loading the items in your roof box. You should place your luggage perfectly in the box so that the weight can remain balanced and distributed evenly. Choosing the right roof box for your car will help you in this.

It will be a good decision for you if you go on a short drive nearby your house with the loaded roof box so that you can have an idea about how it feels to drive with a loaded roof box on top of your car. You should also check the breaking to see if it create any problems.

It is better to give it a test drive so that you do not need to pull over on the highway to fix anything or make any adjustments to the roof box.

Do Roof Boxes Fit Any Roof Bars?

Thule Atlantis Rooftop Cargo Box

Most of the roof boxes are compatible with most aftermarket roof bars. But roof boxes that are long or designed to carry longer items such as skis, fishing rods will need the extra support of other bars.

Check Your Specifications

Again, if you want to fit a roof box that weighs a little bit more than the roof bar’s weight limit, then you have to add another bar or two to keep the box stable on top of your car. 

Adding the extra roof bars around the original rack or slide will help you evenly distribute the weight of your roof box to your roof bars. The extra bars will ensure safety and security, and they will not interfere with the original rack or bars.

If you want to install a roof rack or roof bars on top of your car by yourself or if you want to replace an old roof rack, you should do some research and make sure that it will fit with your roof box. You have to line up the holes for the bits and bolts.

Roof Cargo Bags as an Alternative to Cargo Box

SUAOKI Roof Top Cargo Bag

If you could not find the perfect roof box for you or have issues fitting a roof box on top of your car, you can go for the cargo bags. It is also a beneficial way of increasing the storage capacity of your car.

Follow Instructions

If you want to install your roof box or roof bars perfectly on the roof of your vehicle, you should install the roof box by following the instructions that come with your roof bars and roof box. If you don’t do that, you can face any problem while you are on the way. 

So if you are confused about anything, go and check the instructions and make sure everything is correct. 

Moreover, it would be best if you studied the combination of roof bars and roof boxes that you have chosen for your car because both your bars and box manufacturers should have some compatible products designed for the product you have brought.

They should also mention the maximum weight capacity that the box and bars can take together. So you should carefully decide which one you should buy so that you can travel safely and prevent the roof of your car from being damaged once the box and bars are mounted.

Will Roof Racks, Bars, and Boxes Damage My Car?

secure in place

If you carefully follow all of the instructions by the manufacturer, you will not face any problem, and the roof box or roof rack will cause no damage to your car.

Mind Your Backs

While packing your roof cargo box, you should load maximum weight at the lower end of the box. The manufacturer also recommends it. So you have to be careful. Moreover, roof boxes are bulky things, and they are hard to handle for just one person.

You need anyone to help you mount your roof box on the bars. It will also keep the car from being dented, scratched, or damaged. Moreover, the manufacturer may have recommended a maximum speed limit when you’re driving with the box.

So you should carefully read the manual. If you drive over the speed limit with the roof box installed, then you may face problems, or you might need to stop and fix it before you cause an accident.

When you are installing the roof box, you should also be careful tightening the screws. If you leave it slack, it will shift on the bars and make noises again, or if you make the screw too tight, then it can damage your roof bars and the box. So you have to keep it in a perfect position.

You also have to be careful that you should not go by under a short bridge or go into a parking garage with the roof box installed on top of your car. Because if you hit a low-hanging beam, your roof box can be damaged.

Moreover, the bars or rack also can be damaged or come off from the roof of your car and can cause costly damage to your vehicle. So be very careful if you do not want to spend a lot of money on a roof box.

How Far Apart Should the Roof Bars Be?

When you are spacing roof bars apart, you have to keep in mind that the further you keep them apart, the harder it will be for them to support your roof cargo box’s weight. Most manufacturers recommend that bars should be spaced at a maximum of twenty-four inches apart. So make sure that this standard applies to any crossbars that might go along with the rack that is currently in place.

You will need extra support if you want to carry heavier items with your roof box. Adding a different bar or two will help the box in distributing the weight of the bulk.

You have to space the bars at an equal distance from one another so that the box can be evenly supported by the bars. Most roof boxes are made out of hard plastic, so if they fall on the roof of your car, then your roof of the car can be get scratched. A cargo bag also can drop and touch the top of the vehicle.


Check your vehicle’s owner’s manual to know the roof of your car’s maximum weight capacity so that you can decide how many bars will be needed to secure the roof box.

You have to determine what you want to carry with the roof rack and make sure that the roof rack is compatible with that thing. You also have to make sure of the safety and add more bars if needed so that the item you are carrying cannot damage the roof of your car.

If you are confused about whether you should stick with what you have or not, then you can look for advice from a professional. He will help you know which combinations are best and even help you prepare your car before attaching the roof box.

What’s the Best Position for Roof Box on Car?

Best Position for a Roof

It would be best if you spread the stuff’s weight as evenly as possible so that the roof box could not shift hard and you do not have to take any emergency break to make any changes to the box.

If your load is too heavy, you should put some weight in the trunk to make the car more aerodynamic and help airflow.

Last but not least, the less drag on the car, the better it will be for your fuel economy.

Safety Considerations

An overhanging roof box at the front can interfere with your front view and make it dangerous to drive your vehicle. Roof boxes are usually designed to place them more to the back.

Moreover, it would be best if you always remembered how far back you had mounted the box so that you can open the trunk door without damaging it with the roof box. You should keep an inch or two space between the back of the roof box and the trunk door.


If you have read the full article, we hope it will be beneficial while installing a roof cargo box on top of your car by yourself.

-our editorial board has reviewed this article and has been approved for publication according to our editorial policy.

Best Seller List of Rooftop Cargo Boxes:

Bestseller No. 1
Thule Pulse Rooftop Cargo Box, Medium
  • Functional rooftop cargo box provides 14 cubic feet of additional packing space
  • Rugged and durable design keep contents protected
  • FastGrip quick-mount system assembles in minutes
  • Passenger-side opening for easy loading and unloading
  • Central Locking system provides maximum safety
Bestseller No. 2
SportRack Vista XL Rear Opening Cargo Box
  • 18 cubic foot (510 L) internal cargo capacity
  • Made from durable UV-resistant ABS material
  • Rear opening for easy access away from traffic
  • Tool-free mounting hardware for easy installation and removal
  • Includes key and lock to secure contents in the box, and the box to your rack
Bestseller No. 3
JEGS Rooftop Cargo Carrier | Hard Car Top Large Luggage Box | Waterproof Storage | Heavy Duty Solid...
  • SECURE & PROTECT YOUR GEAR in this 18 cubic ft. HDPE plastic hard shell car top cargo carrier; high-capacity interior dimensions 57 L x 38 1/2 W x 17 3/4 H inches; aerodynamic design for fuel efficiency
  • WATERPROOF STORAGE FOR YOUR LUGGAGE with a four corner locking system, front latch, and weather-tight seal for ultimate car rooftop protection and security
  • EASY & CONVENIENT LOADING AND UNLOADING from either side of the car make for smooth travel and hassle-free storage
  • NO TOOLS REQUIRED, EASY ASSEMBLY AND INSTALLATION. All mounting hardware and simple instructions are included to get you safely on the road quickly
  • MADE IN USA, LIMITED LIFETIME GUARANTEE. The JEGS Rooftop Cargo Carrier’s high-quality construction and performance give you peace of mind
Bestseller No. 4
Thule Force XT Rooftop Cargo Box, Sport
  • A versatile roof-mounted cargo box for everyday use
  • Narrow design leaves space for other gear such as bikes, kayaks, skis, and more while providing 11 cubic feet of additional packing space
  • Designed to fit a wide range of vehicles; works with most factory and aftermarket roof racks
  • Quick and tool-free PowerClick mounting system "clicks" when roof box is secure and properly mounted - takes less than 5 minutes to install
  • Dual-side opening for easy access to all areas of the box, from either side of the vehicle
Bestseller No. 5
Waterproof Heavy Duty Hard Shell Roof Top Mount Car Storage Travel Luggage Box Cargo Carrier with...
  • ▶️ This roof top storage box is universal fit for mounting to max 13 inches wide cross bar, please check the dimension before purchase.
  • ▶️ The package comes with [1] 53 inches length storage box, [2] security lock key, and [4] heavy duty tool free installation mounting brackets.
  • ▶️ It is constructed of rugged, impact-resistant ABS material to ensure a long lasting life in outdoor conditions. More, it can open from the side and stay open till you close it with the strong support arm.
  • ▶️ Opens on the passenger side to 14 inches wide to store bulky items from the side and stays open till you close it, and it is very easy to install without any tool required to assembly.
  • ▶️ Overall Dimensions: 53" L x 34" W x 15" H | Capacity: 11 Cubic Feet and up to 110 LBS
Bestseller No. 6
UBASE Upgraded Rooftop Cargo Carrier, 15 Cubic feet 100% Waterproof Car Roof Bag with Anti-Slip Mat,...
  • 【Large Capacity Rooftop Cargo Carrier】: UBASE roof bag was designed to solve the problem of limited storage space in the car. It can easily storage 2 sleep-bags, 1 tent, 1 yoga bag, 1 hiking bag, 2 medium luggage.
  • 【Most Safe Vehicle Cargo Carrier】: There are 2 long transverse straps trussing up the objects in the bag to avoid them moving. You can fasten the bag with 6 buckles to avoid the bag being torn into 2 pieces by heavy burden. The equipped anti-slip mat to keep the cargo bag stay in place even in high speed road or bump road, no slip, no scratch to your car.
  • 【100% Waterproof Cargo Bag】: It’s made of super thick HIGH DENSITY 500D PVC material, which is 100% waterproof and very strong. We use heat to melt PVC fabrics and press them together with machine process to avoid any slits. It’s sealed with upgraded waterproof zipper. There is a widened zipper flap that helps keep your items 100% dry.
  • 【Universal Cargo Carrier】: Our upgraded rooftop cargo carrier fits for any car, truck, or SUV. you can use straps to fix the cargo carrier with your car rack, or you can use the hooks to fix the cargo carrier to the inner frame of door.
  • 【Fold It When It’s Empty】: We put a storage bag in the box for you. You may fold it when you don’t go out. It can keep the bag clean and save room for you.
Bestseller No. 7
Thule Motion XT Rooftop Cargo Carrier, XL , Black
  • Roof-mounted cargo box provides 18 cubic feet of additional packing space
  • Designed for optimal space efficiency, aerodynamics, and vehicle fit
  • Quick-mount system "clicks" when roof box is secure and properly mounted
  • Dual-side opening for quick access from either side of the car
  • Easy to open and close with grip-friendly handles and supporting lid-lifters
Bestseller No. 8
Vetoos 21 Cubic Feet Car Rooftop Cargo Carrier Bag, Soft Roof Top Luggage Bag for All Vechicles SUV...
  • 【OVERSIZED 21 CUBIC FEET】Massive 21 cubic feet (L52" x W39.5" x H17.5") of space can easily hold all luggage of a family of 5-6. Most other roof cargo carriers are small and there is not enough room to accommodate everything you need.
  • 【HIGH DENSITY 700D PVC】Features triple-layer high density 700D PVC fabric. This material is 1.5 times stronger than 500D PVC fabric, which most other rooftop bags adopts and can easily rip. The coated surface can effectively protect your luggage against rain, grit, snow, wind and sun on the road.
  • 【UPGRADED WATERPROOF ZIP】While other rooftop carrier bags let in water through the normal zipper, we've upgraded it to a waterproof zipper and fitted it with a widened 4.7" zipper flap that helps keep your items 100% dry.
  • 【REINFORCED STRAP SEAM】We notice that the straps of other cargo bags can easily rip from the seam, so we doubly reinforced the strap seam. And all seams of this cargo bag are heat welded and stitched to ensure they are watertight.
  • 【FIT ALL CARS】Whether your car is with roof rack or not, the 4 door hooks and 8 strong straps can always secure your roof top carrier bag. In addition, the equipped anti-slip mat can keep the cargo bag stay in place even in high speed road, and protect your car roof from scratches and damage.
Bestseller No. 9
MeeFar Car Roof Bag XBEEK Rooftop top Cargo Carrier Bag 20 Cubic feet Waterproof for All Cars...
  • 100% WATERPROOF &TEARPROOF MATERIAL - Made of 100% waterproof material, 700D PVC tarpaulin, Grid material with High frequency voltage technology, durable and heavy duty style bag;
  • EASY TO USE - The MeeFar XBEEK roof bag come with 1x anti-slip mats, 1x luggage lock, 6x security hooks, and 1x storage box, it can be quickly and easily installed in minutes; Made of soft shell material, it can be folded into the storage bag to save space while not in use;
  • UNIVERSAL COMPATIBILITY - The MeeFar XBEEK roof bag can be used with any sized car or SUV, work both with car with or without roof rack;
  • MORE SECURITY - Come with BONUS combination lock, it will not only prevent the zippers from slipping, but also adds security to luggage;
  • LARGE STORAGE SPACE - 20 cubic feet 51” (L) X 40” (W) X 17” (H) rooftop cargo bag allows you to hold 4-6 suitcases, travel luggage case, tents, sleeping bags and more.
Bestseller No. 10
21 Cubic Ft Rooftop Cargo Carrier For Top Of Vehicle, 100% Waterproof Soft Roof Top Luggage Cargo...
  • 21 CF ULTRA-LARGE STORAGE CAPACITY: To expand the limited spaces inside vehicle, the rooftop cargo bag provides 21 cubic feet oversized car roof storage space, roof cargo bag dimensions: 52’’L x 39’’D x 18’’H, the roof rack cargo carrier can be easy to hold luggage for your family of 6-8 persons, 4-6 suitcases, travel luggage, tents, sleeping bags and more .
  • 100% WATERPROOF PROTECTION: Made of premium quality 840D tarpaulin material, with water proof PVC coating inner and outside layers, INNOVATIVE DESIGN - seamless whole piece fabric on the bottom to avoid wet and keep cargo dry and clean, leading heat welded technology, water-proof zipper with widened flap, ensures the roof cargo carrier durable to withstand rain, grit, snow, wind weathers .
  • MOST SECURITY STRUCTURE: Equipped with 10 strong wide straps + 2 cross long straps, a free anti-slip mat , all-rounded to fix the car roof bag in place, no slip and no scratch to your car top, maximum secure your luggage at any highway speed trip, the BONUS combination TSA lock, added better protection to your luggage when take a break on the road .
  • FIT FOR CARS WITHOUT/WITH RACK : The vehicle cargo carriers well works for all hardtop cars with roof rack or without roof rack , comes with 6 security hooks, even if there is no roof side rails or roof rack on your top of car, you can buckle it into the car door frame easily, this car roof cargo carrier fits any sized cars, SUV, vans and medium to large sedans, etc .
  • EASY TO INSTALL AND STORAGE : The car top carrier roof bag has been in solid construction already , you can easy install in minutes and start your journey , Alternative to the hard shell roof cargo carrier made of soft shell material, which can be folded into the storage bag in small size to save space, simple cleaning with a couple of wipes, and ready for next time journey !

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Last Update : 2022-01-13