Should a Roof Box Overhang a Windscreen?

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Yearly, roof boxes are becoming more popular due to the sheer number of benefits they offer the avid camper, road tripper, and adventurer. But, there’s an abundance of different brands, sizes, and shaped cargo rooftop boxes you can invest in. Because of this, not all sizes fit the entire catalog of cars, SUVs, and trucks. Therefore, when installed, should a roof box overhang a windscreen?

If a cargo roof box overhangs a windscreen, it isn’t considered a significant problem if it’s tightly secured onto the vehicle. However, from the overhang, the aerodynamics of the vehicle will plummet. When this occurs, your miles per gallon (MPG) will increase immensely.

Having a roof box is excellent, but paying additional MPG isn’t. Therefore, you’ll want to try and create a seamless transition from the windscreen to the box if your extra storage unit allows for it. By doing this, the force caused by traveling forward has a place to go, rather than hitting the underneath of the box. To better understand how to reduce this, along with other helpful-to-know queries based around the topic, we recommend you become knowledgeable on the below:

Should a Roof Box Overhang a Windscreen? is It Really Matters?

Can a roof box overhang the rear?

As you’re now aware, overhanging a rooftop cargo box above a windscreen can cause aerodynamic issues, which can potentially increase your MPG. Because of this, many people think it’s a bright idea to move the storage unit backward and allow it to overhang the rear. But is this practical?

If you’re looking to decrease the enhanced MPG levels, then overhanging your box on the rear of your vehicle is much better than your front windscreen. This is because the primary force causing this increase in MPG is coming from the vehicle’s front while traveling.

That being said, there are some downfalls to overhanging a roof box on the rear. Depending on which type of vehicle you have, it could potentially reduce the accessibility of your bonnet. The likelihood of you using the boot while traveling is relatively high because of its superb storage space.

But, this really depends on what type of vehicle you currently have. Some car bonnets have been developed in recent years that don’t require the whole backend to open when you want to gain access to the boot. Instead, the back windscreen and a small rectangular section will be required to rise to allow you entry to a boot. If you have a car model like this, you might be able to overhang your roof box more than vehicles with a traditional boot type.

To conclude this, overhang on a vehicle’s rear end isn’t the end of the world if it doesn’t restrict access to your boot. Again, you just need to ensure that the load is secured onto your rooftop and isn’t showing any signs of movement.

How to reduce overhang with a roof box

Now you understand more above overhang with both the rear end of a vehicle and its windscreen, can you reduce this? Unsurprisingly, yes. Ideally, you’ll want to consider the below before investing or fixing a cargo roof box for your mortised vehicle.

  • Measure twice – In the world of rooftop cargo boxes, you’re able to purchase various sizes, brands, models, and much more. There are thousands of different options which come in various measurements. Therefore, you’ll want to accurately measure your vehicle’s rooftop before making the initial investment in a cargo box. By doing this, you’ll dramatically decrease the possibility of the box being too large or small. From just taking the time of day to perform this task could increase the longevity of your box, along with making your vehicle’s fuel consumption much less.
  • Positioning – If you’ve already purchased your cargo box, then you might want to alter its positioning to reduce overhang if possible. To reduce the overhang on either the front windscreen or rear, you’ll need to move the crossbars to which the cargo box is attached. Usually, you can move these the entire length of the roof rails. Therefore, that should be enough to play around with. Notably, if you had to choose the option of front or rear overhang, we’d choose rear if you don’t require access to your boot.
  • Vehicle type – A more expensive option is your actual vehicle type. Some vehicles that are manufactured just aren’t built with rooftop cargo boxes in mind. Because of this, a small majority of cars don’t have rooftop boxes suitable for their size. If you encounter this problem, you might want to consider alternative options like a cargo bag, as these are much smaller in dimensions.

The above outlines the three primary considerations you need to think about when trying to reduce cargo box overhang. Without a doubt, you’ll want to try and eliminate this as much as possible because of the sheer inconvenience it could cause.

What size roof box do I need?

In the rooftop cargo box world, we mentioned various different sizes are dependant on the models and brands, etc. But how do you accurately determine which size roof box you need? Typically, you’ll be presented with three different types of cargo boxes. Which include:

  • 1/2 width – is suitable for a mid-sized car
  • 3/4 width – is suitable for a large-sized car
  • Full width – is suitable for a large-sized estate car

Ideally, you’ll want to go off the above measurements. However, it doesn’t mean you can’t fit a 1/2 width-sized cargo box on a large estate car. You can use this for both mid-sized and larger cars. As primarily, vehicle owners use these and store other types of specialized rooftop storage equipment like bike racks, etc.

Your safest bet is to consider the above and quickly perform a Google search on what size your vehicle is considered. By doing this, you’ll dramatically reduce the occurrence of overhang, increase your MPG with a roof box, and grant yourself access to the boot. These benefits alone should be a good enough reason to think about the above size guide and implement it accordingly.


After reading the above, you should have a better idea of whether a rooftop cargo box should overhang the windscreen on a vehicle. Ideally, not. However, it isn’t a problem if it doesn’t block any visuals and is securely tightened onto the roof rack. 

About the author 

Vieira Babeker

Hi! I'm Vieira. I've always been interested in different Auto Accessories

My passion here at is to provide helpful straight forward clear advice and tips for Automotive Accessories.

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