Thule Force XT XL Roof Box Review

The Thule Force XT XL is an 18 ft³ / 510-liter roof box (or cargo box) that’s easy to open and install and was one of the first things I purchased for my Subaru Outback. I’ve now driven over 20,000 mi / 32,000 km with it and have used it to carry everything from snowboards and skis to crash pads and backpacking gear.

It has two interior straps for securing gear (like skis or a snowboard) and an additional strap that hangs down on either side to make closing the box easier.

Thule Roof Boxes Compared

There are several Thule cargo boxes (which we shall call roof boxes here), and it might seem intimidating trying to figure out why some are so much more expensive. Your first mission is to figure out which roof box is going to fit your vehicle and to make sure that you’re still going to be able to open your trunk with the roof box on your vehicle (and if you’re going to like how it looks with the roof box potentially moved all the way forward). The $1,000+ Vector roof boxes are fancy and have built-in lighting and a felt-lined interior. They may be a good option if you delicately want to transport costly (and fragile) things.

Testing Conditions

I have been using the Force XT XL for over a year and have driven close to 20,000 mi / 32,000 km with it attached to the top of my car. I have taken it off and put it back on multiple times. I’ve used it through winter (snow/below-freezing temperatures) and summer (100°F+ / 38°C+ environments).

The Specs

• Volume: 18 ft³ / 510 liters
• External dimensions (in): 82.75 x 33.75 x 17.25
• External dimensions (cm): 210.18 x 85.72 x 43.81
• Internal dimensions (in): 77.5 x 29.5 x 15.25
• Internal dimensions (cm): 196.85 x 74.93 x 38.73
• Height off crossbar: 16.1 in / 40.89 cm
• Load capacity: 165 lb / 75 kg
• Mounting system: PowerClick
• Weight: 47 lb / 21.3 kg
• Locking system: Central lock
• Locks included: Yes
• One Key System compatible: Yes
• Load capacity skis (pairs): 5-7
• Load capacity snowboards: 3-5
• Max length of skis: 195 cm
• Keys Included: 2
• Color: Black Matte
• Model number: 635801
• MSRP: $799.95

The Features

• The forward position allows trunk access with a lesser risk of contact with the roof box.
• It fits a wide range of vehicles
• PowerClick quick-mount system
• LockKnob prevents damage to the Thule Comfort Key
• DualSide opening allows access from either side of the vehicle

The Good

The Attachment

You might imagine it a difficult task if you’ve never put a roof box on a car. You would be wrong. The most challenging part of attaching the Thule Force XT XL to your vehicle is the initial lifting it onto your car. Although one person can do this (I’ve done it alone many times), it’s far easier with some help. Once the roof box is on, you need only make sure it’s centered, and then you need to tighten down four locking mechanisms from the inside onto your crossbars. Tighten each of the four until they click, and you’re done.

The Waterproofness

I would assume most roof boxes would have to rank highly for this, but just in case there’s any doubt, I can attest to the fact that the Thule Force XT XL is waterproof. I’ve taken it through rain, snow, and carwash (note, this is me washing the car—don’t take it through one of the automatic car washes) without any evidence of water intrusion.

The Locking Mechanism

Closing and locking the Thule Force XT XL is easy and can typically be done without much trouble. You need to ensure that 1) nothing is blocking any of the three locking/connection points between the top of the box and the bottom, and 2) your gear isn’t stacked so high that it prevents the box from closing. I’ve also used (extensively) the Yakima equivalent to the Thule Force XT XL and have found the Yakima to be a nightmare when closing – the hinges go out of whack, the box doesn’t line up, and the lock won’t engage. Thule is the clear winner here.

The Customer Service

I haven’t interacted with Thule much, but after talking to them regarding my Thule Force XT XL and the bike rack I purchased from them (the Thule T2 Pro), I am thrilled with the level of customer service they offer. Should I encounter any future issues with my roof box, I don’t think there will be many difficulties resolving things with Thule.

The Okay

The Buttons

There are these little black buttons (things?) spaced around the outside of the Thule Force XT XL. I’m not entirely sure what they are or what purpose they serve. Maybe they’re entirely aesthetic? Regardless, they come off slowly over time and I’ve found myself pushing them back in every once in a while. I’ve managed to lose a couple which just means I have small metal rings in the place where the button used to be. Not great?

The Gas Mileage

As you might expect, putting a large box on top of your car changes its aerodynamics. Aerodynamics affects your car’s gas mileage. I have this box on a 2019 Subaru Outback and have noticed a 3-5 mile per gallon (1-1.7 km/l) drop in my gas mileage when using the Force XT XL. I can’t wait for that all-electric Outback to be released (and announced).

The Bad

The Moon/Sunroof

One of the things I made sure my car had when I bought it – a moonroof. One thing that the Thule Force XT XL covers in its entirety? The moonroof (or sunroof). Quick aside, generally, the difference between a sunroof and a moonroof is that a moonroof is tinted – a sunroof is not (it lets the sun through). Having this box on top of your car means goodbye sun/moonroof. You can still have it cracked or open for airflow, but it’s really not the same. My moonroof has become something more resembling a ceiling vent.

The Removal

Attaching the Thule Force XT XL may be easy, but taking it off is a bit of a pain – at least with one person. I can get the box on and off by myself (so long as it’s empty), but it is a pain. I should probably try doing this with help in the future. I can’t imagine a similarly-sized box would/could be any easier to take off, but it’s a pain nonetheless.

Wrap Up

The Thule Force XT XL is an awesome roof box with which I’ve had zero problems after tens of thousands of miles of driving and dozens of trips in all kinds of conditions. Sure, washing my car’s roof has become a near impossibility since I hate taking the thing off and then putting it back on, but that’s a small price to pay for all of the added cargo room.

Questions, comments, or personal experience with the Force XT XL? Leave a comment below and let me (us) know!