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How to Buy a Roof Cargo Box and Crossbar Setup

How to · Auto

How to Buy a Roof Cargo Box and Crossbar Setup

A roof box solves trunk overflow, but the hardware adds up fast. Here is how to time your buy and spread the cost.

VoAtlas editorial Updated · 3 min read
Typical cost $850 before anything else
Across the 0% window $56.67/mo 15 months, no interest

How we got that: $850 spread evenly across the 15-month introductory window on the Discover it® Cash Back. Checked · at the bank Carry a balance past the window and the standard APR applies to what is left.

Packed cars are miserable on a long drive, and a roof box gives you back your legroom. But between the box and the crossbars required to mount it, you are looking at about $850 for a decent setup. Prices usually soften right after the summer road trip rush or just before winter ski season kicks in, so timing matters just as much as the gear itself.

Before you even look at payment methods, check if you can negotiate on the crossbars or installation at local rack shops. Once you have your best price on the hardware, you can map out how you want to handle the cash flow without draining your checking account all at once.

Remember that the 0% intro APR for 15 months on purchases is a deadline, not free money. If you still have a balance left on that $850 when the 15 months run out, standard interest charges will kick in on whatever is left over.

The steps

  1. 01

    Time your purchase

    Aim for the shoulder seasons right after summer road trips wind down or just before the winter ski rush. Retailers often discount inventory during these transitions to clear shelf space. Keep an eye out for bundled deals where buying the box and crossbars together saves you a chunk.

  2. 02

    Negotiate the total setup

    Do not just look at the price of the cargo box. Crossbars, towers, and fit kits add up fast and are often where shops have the most markup. Ask if they can throw in the installation labor or shave a bit off the crossbars if you buy everything as a package.

  3. 03

    Map out your payment window

    If you decide to space out payments rather than paying cash today, look at the math. Spreading $850 across the Discover it® Cash Back 15-month intro window on purchases comes out to $56.67 per month. Setting up autopay for that exact amount keeps you on track without you having to think about it.

  4. 04

    Test the fit before you leave

    Once your gear arrives or gets installed, load it up in the driveway. Check that your trunk can still open all the way without hitting the back of the box. Take it for a quick highway test drive to make sure the crossbars do not create an annoying whistle at speed.

  5. 05

    Keep an eye on clearance

    Measure your garage door clearance with the box mounted before you pull inside. It sounds obvious, but forgetting the extra height is an expensive mistake. Take a photo of the new clearance height with your phone and keep it on your dashboard as a reminder.

  6. 06

    Check the card terms before you commit

    Every figure we publish for the Discover it® Cash Back carries the date a person verified it against Discover and a link to where they checked. Intro windows and APRs change without notice, so confirm the current terms before applying.

    See Discover it® Cash Back terms →

Common questions

Do I need specific crossbars for my car roof?

Yes, crossbars are vehicle-specific based on whether your car has raised rails, flush rails, naked roofs, or fixed points. Buying universal bars that do not fit right can damage your car roof or let the box shift at highway speeds. Always check the manufacturer fit guide before ordering.

Will a roof box ruin my gas mileage?

It will definitely drop your miles per gallon, usually by about 10 to 25 percent depending on the box shape and your driving speed. Wind drag is the main culprit here. Take the box off when you are done with your road trip or ski season to save gas on daily commutes.

How much weight can my car roof actually hold?

Most car roofs have a dynamic weight limit—meaning when the car is moving—of around 150 to 165 pounds, which includes the weight of the box and crossbars themselves. Check your vehicle manual for the exact limit. Exceeding it can damage the roof structure.

Are soft roof bags a good alternative to hard boxes?

Soft bags are cheaper and easier to store in a closet when you are not using them. However, they are not waterproof in heavy downpours, offer zero security against theft when you stop for food, and create more drag on the highway.