The Bike List

Mont Blanc Triton 400 roof box £360 (black) or £325 (silver)

Tested by Jon Adams, tester for The Bike List

Compared to other outdoor activities, cycling is pretty gear-intensive. There's the bike itself for starters, but by the time you've added the specialist clothing, shoes, helmet, lights, backpack, water bottles, spares and tools, you'll have built up a pretty sizeable pile of kit. Add this to the other gear you're already taking, and it's very easy for two or three cyclists to fill a car, no matter how much room you thought you had in the boot.

Carrying the bikes is one challenge, and our review of the Mont Blanc Discovery carrier may help with that, but finding somewhere to stow all the extra clobber is the next problem waiting in the wings for you. If your gear won't fit comfortably in the vehicle once the passengers are in, then assuming you don't want a trailer, a roofbox will come to the rescue. As the name suggests, these are big, ABS plastic boxes that sit on the roof of your car and free up about a boot's worth of interior space. They come in various sizes and shapes, with capacities from around 300 litres to over 600 litres, and the model we tested is the Mont Blanc Triton 400, which offers 390 litres of space.

The Triton sits in Mont Blanc's pricier Performance range, and offers a sleeker, more sculpted finish and a more convenient attachment system than the less expensive Classic range. The Performance models also offer three-point central locking and gas-powered struts to assist opening - all nice things to have when it comes to fitting, packing and unpacking a roofbox.

What's special about the Triton 400 is that it's a half-width model, and that means you can use it alongside roof-mounted cycle carriers. You need to have roofbars fitted to your vehicle, and the ideal choice are the 'aero' or oval-shaped aluminium bars that offer a central channel for attaching items. We used Mont Blanc's RF 20 bars (£100), but any make should be fine as most aero bars are interchangeable. The Triton is also compatible with the cheaper square roofbars - these don't have the channel though, so you have to use the supplied clamps for fitting boxes and carriers.

With the bars on, centred up and locked in place - a 10 minute job if you've never done it before, or 5 minutes if you have - it's hard not to be a bit daunted by the prospect of getting the Triton 400 into place. At 226cm long, 65cm wide and 38cm deep, it's pretty huge. And though it's not too heavy at 17kg, the sheer bulk of the unit will have you wondering how on earth you're going to manage the task.

But you needn't worry, as it's actually rather easy, and even though I'm on the short side at 5'6", I managed to fit the large, cumbersome-looking object to a high-roofed VW Touran MPV without any help at all in about 5 minutes flat. The key is to assemble and arrange the four internal attachment points first, and then you simply hoist it over your head, rest it on the roofbars and manoeuvre the bolt heads into the channels. Slide it in, position it how you want it, then twist and fold over the four camming locks (a set of steps might be handy here), and the job is done.

The attachment points themselves are square-headed bolts that thread through long slots in the base of the box, pass through a metal bracket and screw into a camming handle that sits inside the unit. With the bolt's head in the roofbar channel and the camming arm locked down inside the roofbox, you have four very secure clamps fixing the box in place.

There's just one keyhole that secures the Triton 400's lid, and this operates all three locks that are positioned at the front, centre and back of the box. It's a mechanically-operated central-locking system, and a smart mechanism prevents you from taking the key out of the keyhole until the box is closed and locked, so your keys can't fall out when you're rummaging for some vital item in the dark. You can get left- or right-handed boxes, with the opening on one side and the hinges on the other, but you can't swap them round, so which side you want to mount and load the box from needs to be decided at the time of purchase.

When it comes to loading the box, you need to exercise some care. It'll take a lot of stuff, but you should be concentrating on the bulkier, lighter items rather than the smaller, heavier ones. Think sleeping bags and pillows rather than toolboxes and tent poles and you won't go far wrong. The thing is, though the Triton 400 will happily take a load of 75kg, your car's roof may not, so you need to add everything together and ensure you don't overload the maximum load your vehicle can take.

Look up your roof's max load in your vehicle's handbook , and if it's a typical 100Kg, then you need to add all the various weights together and make sure you don't exceed this figure. Roof bars and feet are about 5kg, a couple of roof carriers will be around 8kg, bikes will be up to 30kg for a pair, and the Triton 400 is another 17kg. This all comes to about 60kg, so you've only got 40kg left for the contents of your roofbox. This is still a decent amount, but is only the equivalent of two holiday suitcases, so stick to the stuff that takes up room but doesn't weigh too much.

Your car's performance and handling will be affected by a roofbox. You won't be able to go as fast, your fuel consumption will deteriorate a little and the increase in wind noise and whistling will be noticeable. To minimise the latter, tape up all the holes and slots with electrical tape (or fill them with the rubber strips provided with the Triton), and position the roofbox as far back as possible. To determine this, open the tailgate fully and make sure the roofbox can't touch it. The ideal position is to have the nose of the box behind the windscreen's airflow, but that's not likely to be possible on most cars with the Triton 400's length of 226cm.

Aside from extra noise and slightly dented fuel economy, the only issue we had with the Triton was that the keyhole can stick a little, making key insertion tricky. Its position on the side of the box leaves it exposed to lots of weather and road grime, so it needs a regular squirt from lube to keep it nice and free. The other option is to tape it over when you're all packed (or not using the roofbox but leaving it on the car) - keep a roll of tape in the door pocket nearest the lock and it's not too hard to remember. It's not a big issue, but some kind of protective lock cover would make sense to avoid either of these bits of preventative maintenance.

Minor lock niggles aside, the Triton is an excellent way to extend your car's storage space. It comes in silver or black, and its sleek, sculpted curves ensure it looks rather nice in place, too. The gas struts assist in opening and ensure it stays open when loading or unloading, and the quick release cams make it a breeze to fit or remove. The central locking system makes it quick and easy to secure your stuff, and the 390 litre capacity takes a whopping load alongside your bikes. The suggested price of £360 for the black finish or £325 for the silver appears steep, considering you can get a roofbox for under £200, but it is a premium model and is in line with similar specified unit on the market. On top of this, we've seen the Triton 400 for around £250 at some sites, so it's well worth shopping around for a great deal.

Buy from:

Mont Blanc says:

Stylish roof boxes with excellent aerodynamic qualities. Complete with smooth opening gas struts and secure-assure locks, which means you cannot remove the keys unless the box is properly closed.

  • Gentle gas struts for soft opening and closing of box.
  • Three point central locking.
  • Load securing straps included.
  • Flexible attachment to the load bar.
  • Unique quick attachments - the box is attached from the inside.
  • Fits both square bars and aluminium bars with C-slots.
  • Left or right hand/driver's side opening.

Technical specification:

  • Volume - 390 litres
  • Dimensions (inner) in cm: Length 226 (221), width 65 (60), height 38 (37)
  • Fits aero bars - Yes.
  • Fits Square bars - Yes.
  • Weight - 17kg.
  • Material - UV resistant ABS.
  • Security - Key cannot be removed until locks are properly engaged.
  • Min-max distance between front & rear bars = 560-1040mm
  • Opening size 38cm

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At a glance

Verdict Half-width roof box that stashes a 390-litre load alongside a couple of bikes. With gas struts for opening and a central locking system, it’s well featured, and it looks the part, too.