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, simple to 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 that can be used to secure 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 a number of different 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 than others. 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). Basically, just know that the $1,000+ Vector roof boxes are very fancy and have built-in lighting and a felt-lined interior. If you’re very delicately wanting to transport costly (and fragile) things, they may be a good option.

Testing Conditions

I have been using the Force XT 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 both 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: $629.95

The Features

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

The Good

The Attachment: If you’ve never put a roof box on a car before, you might imagine it a difficult task. You would be wrong. The most difficult part of attaching the Thule Force XT to your vehicle is the initial lifting it onto your car. Although this can be done by one person (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 tighten down four locking mechanisms from the inside of the roof box onto your crossbars. Simply tighten each of the four until they click and you’re done.

The Waterproofness: This is something I would assume most roof boxes would have to rank highly for, but just in case there’s any doubt, I can attest to the fact that the Thule Force XT 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 is easy and can typically be done without much trouble. You just 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) that 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 and have found the Yakima to be a nightmare when closing – the hinges go out of whack, the box doesn’t line up, the lock won’t engage. Thule is the clear winner here.

The Customer Service: Thule is a company I haven’t interfaced with much, but after having talked to them regarding both my Thule Force XT 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 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 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 that I’ve had zero problems with after tens of thousands of miles of driving and dozens of trips in all kinds of conditions. Sure, washing the roof of my car has now 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!