The Topeak MTX TrunkBag DX carries quite a bit in its 12.3L capacity, whilst staying mostly tucked in the slipstream and proving very easily removable. The top is usefully expandable, the build is absolutely fantastic and it does everything you ask of it – everything but keep full bottles in its rear carrier over rough ground, that is.
Topeak's MTX bag range has been around for as long as I can remember, and the stalwart DX and DXP (P is for panniers) options form its backbone. Go on any audax or long ride in the UK, and chances are you'll see an MTX in use. Fitting pretty much every Topeak rear rack since time began, you are buying into a great deal of design evolution and fine-tuning.
The big thing about the MTX is that it slides on and off your bike in seconds, via Topeak's QuickTrack mount. It's a really solid system – there's simply no way the bag is coming out of its channel other than by sliding backwards. What stops that happening is a very chunky spring-loaded yellow catch, that clicks underneath a bar at the front of the rack.
Packed to the gunwales with the expandable lid all the way up, the MTX DX holds an impressive 12.3 litres of kit. The expanding lid is a highly useful feature, operated by two zips that give enough extra space to stuff a jacket into (if you haven't filled it already).
The interior is bright yellow to make finding things easier, and the adjustable/removable divider can be positioned anywhere on its Velcro tabs. There's also an elasticated (but not zipped) pocket under the lid for smaller valuables.
Outside the lid is a generous mesh pocket, perfect for storing snacks or gloves, and a bungee cord for lashing down bulky things like a jacket, a spare tyre or a small sleeping mat. The bag handle grip is a Velcro-secured tube, and can be undone to allow full access to gear stored on the top.
You also get a removable shoulder strap that's padded and adjustable, to make walking around with the bag more comfortable.
The side pockets are about 4cm wide, and the two zips don't go all the way down the sides; handy to stop all the contents spilling out when opened. The pocket sides are made from a pretty rigid material, so hold their shape well.
For visibility you get a strip of 3M reflective tape, plus a sturdy light mounting strap on the rear bottle holder.
As you'd expect after a few decades of evolution, in use the MTX DX TrunkBag pretty much nails it. Stowing and retrieving food, clothing, tools or whatever is easy, and even fully loaded to the weight limits of the rack (the rather good TetraRack R2) the bag is stable. I like having it out of sight, too, and with the solid TetraRack I didn't notice the pendulum effect of the extra weight after a while.
Being able to quickly slide the bag off at shops or for picnics really is handy: yes, it will fit two bottles of chilled prosecco and a stash of nibbles, with the picnic blanket going on top. Also the side pockets are great for 500ml bottles of real ale (leave to settle on arrival). There may be other uses for the MTX TrunkBag DX, but they currently escape me.
Not that the MTX is perfect. One gripe with QuickTrack is that it doesn't wedge entirely tight, leading to a little bit of a rattle if the terrain is bumpy and the bag is lightly loaded. This is very easily fixed (tape a six-inch strip of inner tube to the load plate) with mere seconds of work, but really Topeak should have added a proper bumper/damper by now.
The second issue is more pressing, yet far less likely to occur. During one extended bout over extremely rough terrain, the yellow latch worked loose. Now I really do mean extreme; like, barely-able-to-hold-onto-the-handlebars rough, for half an hour. Even then, the bag only shifted around 5mm so the clip was just under the retaining bar, and it didn't fall off. I fixed it with a quick shove forward.
So an extreme case, then, but something to be aware of if you're looking to use the MTX for, well, motocross sort of shenanigans.
The bottle holder is a sturdily made, 5in deep pocket with cinch straps either side and a bungee-and-toggle around the top edge. Despite this, a full 750ml bottle ejected itself (twice) over relatively smooth but occasionally potholed/water-barred gravel roads. To be fair, 800-odd grams of slick-sided bottle being violently bounced up and down takes some retaining, and the holder works well on road. It's something Topeak could improve on, though.
These three points are relatively minor in the bigger picture – the MTX DX Trunk Bag really is a great bit of kit that will last you many, many years and miles. For extreme weather there's an optional reflective rain cover for £15, too.
There are plenty of luggage-carrying options available, including panniers and backpacks, but if you're after this sort of design the pickings are slimmer. The Blackburn Local Trunk Bag features some of the MTX DX's functionality for £49.99, plus you can fit in on any rack; the MTX requires a Topeak rack such as the TetraRack R2 at £89.99.
If you don't want a rack at all there are tail packs such as the Rapha Waterproof Rear Pack at £115, but for ease of use, utility and quality, Topeak pretty much owns the rear bag market. Based on my time with the MTX DX, it deserves to.
An excellent way to carry a lot of gear, quickly removable and really well built
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road.cc test report
Make and model: Topeak MTX Trunk Bag DX
Size tested: 12.3L
Tell us what the product is for and who it's aimed at. What do the manufacturers say about it? How does that compare to your own feelings about it?
It's for people wanting an easy on-off carryable luggage solution, for commuting, day trips or possibly longer.
Topeak says the MTX TrunkBag DX features: "...a divided main compartment, two zippered side pockets and rear water bottle holder. Our unique construction process combines molded panels and flexible fabric for rigidity and water repellency. Compatible with all MTX QuickTrack® racks."
Tell us some more about the technical aspects of the product?
Water bottle holder, Shoulder strap
Carrying handle, Elastic top bungees
3M™ reflective strip, Safety light clip
Optional rain cover
* 3M™ is a registered trademark of 3M Company.
BAG ATTACHMENT MTX QuickTrack® system
CAPACITY 12.3 L / 750 ci
COMPARTMENTS 1 divided main, Two side zippered, Multi-expanding top
INSULATION Rigid EVA foam
MATERIAL 600 denier polyester
MAX LOAD Limited to rack max load rating
SIZE 36 x 25 x 21.5-29 cm / 14.2' x 9.8' x 8.5'-11.4'
WEIGHT 985 g / 2.17 lb
Topeak's construction is really top notch, and the materials likewise.
Zips and compartments all work really well. The only real issue is retaining large, full waterbottles over rough ground.
It's not designed to be light, but 880g without the carry strap for 12.3L of storage is OK.
Tell us how the product performed overall when used for its designed purpose
Extremely well. It's pretty much bombproof, and highly useful.
Tell us what you particularly liked about the product
Tell us what you particularly disliked about the product
The rattling when empty (though it's easily be sorted).
How does the price compare to that of similar products in the market, including ones recently tested on road.cc?
Cheaper than a lot of other bags of similar capacity, and as well built as any.
Did you enjoy using the product? Yes
Would you consider buying the product? Yes
Would you recommend the product to a friend? Yes
Use this box to explain your overall score
Functionally the bag is great, and the build is fantastic. If Topeak ironed out the niggles it would get a nine, but as it is the MTX is very good and an eight.
About the tester
I usually ride: Merida Ride 5000 Disc My best bike is: Velocite Selene
I've been riding for: Over 20 years I ride: A few times a week I would class myself as: Expert
I regularly do the following types of riding: cyclo cross, club rides, general fitness riding, mtb, Dutch bike pootling.