Topeak RX Trunk Bag DXP
808g £66
& Topeak RX Beam Rack
665g £59.99

The Topeak RX Trunk Bag DXP conjured up images of an integral pannier and trunk bag put through a matter shrinking device. Though primarily designed for their RX Beam Rack, used solely as a trunk bag it has proven a great fit with Topeak’s Super Tourist DX series - great if you want luggage that’s easily switched between a clutter phobic road build sporting Topeak’s beam rack and an Audax or beast of burden. Several soggy weeks down the line, I’ve warmed to its convenience, neat design and decent weatherproofing.

Pros: Convenient, nicely designed compartments, thoughtful detailing, solid construction, compatibility with RX and X top plates.

Cons: Water resistant rather than waterproof, system specific.

Specification

As I said in my opening paragraph, it’s essentially a trunk bag which expands to 7.3 litres courtesy of the inner “roof” and pannier sides. Look closely and there’s an integrated cargo net and sturdy carry handle.

topeak RX Trunk Bag DXP mounted n bicycle rack

The panniers are neatly tucked away in the zippered sides. Big zipper tags makes access and refitting quick and simple - even in winter weight gloves. Unfolded, the pannier sides are designed to wrap via their elastic cord to the Beam Rack RX side rail hooks.

Topeak RX Trunk Pack DPX mounted on Topeak RX Beam Rack with top raised and integral panniers out.

Measuring 31x20, 5x16-25cm, the bag is made from a very sturdy Teflon coated 600 denier polyester with generously thick foam walls and base to insulate against shock and annoying rattle. Reflectives are bold and effective, without being brash, and there’s a reassuringly sturdy LED tab that has proven a secure host to bigger lights, including the Ravemen TR200.

Internally, it’s a bit more regimented than the larger MTX Trunk Dry Bag cousin, but that shouldn’t be interpreted as restrictive, and, being a bit of a rat packer, some discipline’s no bad thing-especially when trying to find a multi-tool or tyre lever in the arse end of nowhere. The main compartment is yellow, making spotting tools and stuff easy.

Even with the carry handle’s presence, I’ve found it will swallow a tool rocket (pencil case type tool stash), four tubes, multi tool, patch kit, wallet (or change pouch), packable jacket and, with the roof expanded, other small spares and snacks - all without any sign of indigestion. Need more space - drop the sides and you’ve the pannier pockets. These are best for bigger, lighter stuff - think spare pair of gloves, socks, buff, arm/leg warmers, rather than anything weighty. Bought too many bananas at the last rest stop? Slip them beneath the top-mounted cargo net, sorted.

topeak rx trunk bag extended to full capacity and rear light in light loop

topeak rx trunk bag open with inner tubes inside with yellow lining

Mounting hardware

Topeak RX trunk pack base with tracking for attachment to rack

The RX employs a similar track-type attachment as the DX and, as I said earlier, this plays nicely with the DX top plates, but not the other way round - the DX track found on the MTX Trunk Dry Bag is incompatible. Align the grey bag rails with the rack and slide fully home until the yellow “lips” click securely around the rack’s top rail. To release, depress the “lips” while sliding the rack backward. This contributes to the weight, but more convenient than straps and, with a conversion plate, it’s possible to port the bag over to another brand’s beam, or traditional rack top. The solid top plate also serves as a very effective splash guard, protecting luggage and riders from a soggy bottom.

Test bikes & contexts

Ours has served decent amounts of time on Muffin’s Topeak Uni Super Tourist 2.0 Non-Disc Rack and Ursula’s Topeak Uni Super Tourist DX Disc since I was impressed to discover compatibility and wanted to use these as controls, before whipping it over to the Beam Rack RX to see if there were any differences between the two designs in terms of security, wind resistance etc. It’s worth pointing out that if you were seeking something with much greater capacity, the Topeak MTX Quick Track EXP offers a similar package but with bottle holder and 16.7 litres.

Given the RX Trunk Bag is a more minimalist design intended for road and other bikes and where a 4-point rack is incompatible, or undesirable. With this in mind, let’s take a closer look at the Topeak RX Beam Rack. Ours is the E version, which has a horizonal beam, the V has a raised neck.

Otherwise, both are neatly made from 6061T6 aluminium alloy. Welds are the nicer end of workman-like and certainly aren’t going to break. Maximum payload is 15lbs (6.8 kilos), which is again, reassuringly good, especially if you wanted to carry a lock. Along the top channels there are two silicone straps - these are designed for lashing any oddly shaped cargo down - assuming you weren’t running a trunk bag.

The side rails attach to the main rack via two 5mm Allen screws and some long grey composite shims - 5nm is the maximum suggest torque, so have some grease and your wrench handy. A helping of some stout grease on the threads is a good move, too. I’ve opted for Oxford Mint Assembly Grease Oxford Mint Assembly Grease | cycling-not-racing, which is a stoical blend well suited to such duties.

The beam attaches to metal seat posts between 25.4 and 31.8mm courtesy of a hinged and twin bolt clamp with shims to suit. This design is infinitely more secure than those employing a quick-release. The configuration reminded me of an Ahead stem and is more secure since it displaces the load evenly. Measuring (tall) the clamp doesn’t consume much post either, which is good news if you’re switching between bikes of different sizes, or genres.

Then of course, it’s not so easily swiped if you’ve locked up and nipped into the supermarket. These fasten to 8nm, which isn’t particularly high, so it’s important to ensure you’ve introduced the right shim. Denise’s USE is 25.4 (employing a long shim). I found it necessary to create my own shim from scrap butyl, then adding the thinnest of the Topeak.

Maybe I’m over-cautious, but it’s been a good fifteen years since I’ve tested a beam type and recall slippage issues with quick release models, even when very modestly laden. I’m pleased to report this has been a moot point here, even nearing the maximum payload, although I needed to snug the fasteners down following the first couple of outings along lumpy lanes and unmade roads. The silver finish seems similarly well applied and should age more gracefully than black.

Performance 3.75/5

Regardless of host, the Topeak RX Trunk Bag has performed consistently well. Without a fully equipped wind tunnel, it’s difficult to make hard, scientific comment upon the aero properties, but anecdotally, the relatively narrow, compact profile did seem to offer less air resistance, especially compared with the boxier (and notably heavier) MTX during long, blustery early season outings. Another advantage over bigger models is improved saddle clearance, which is good news for smaller riders with less post exposed. 12cm of post should be fine and allows for the bag’s expansion. You’ll still need to find a new home for a post mounted light, but this is a minor consideration.

The foam linings have also done an excellent job of damping vibration and noise - no hint of the tool kit percussion when tackling rumble strips, washboard tarmac and green lanes. It’s also passed my eggs test with flying colours, regardless of rack host. However, I’d still shy away from carrying compact cameras, or similar expensive and sensitive electricals - up front, in the bar bag, or a zippered breast pocket is where they belong.

The folding panniers aren’t lined, or reinforced so, as I said in my opening paragraph, best filled with lighter, bulkier cargo- gloves, micro jacket, arm warmers etc. Either way, no flapping, or distracting bob so long as you’ve tethered the elastic around the “feet”.

Weatherproofing is good, but think highly water resistant, not proof. Topeak offers a waterproof nylon rain cover for foul weather and I’d say it was a worthwhile investment for wintry roads and mucky trails, even though the top plate fends off a decent amount of crap. Lining with sturdier bin bags is the other remedy.

Stock, persistent moderate rain hasn’t presented any major issues, rain just beading up and rolling away, thanks to the coating. When giving bikes a good sudsy bucket wash, I noted some minor ingress in the pockets, which I suspect crept in through the zipper. This led to that reddish taint on some spare chain links and a multi-tool, so whip them out and dry following a wet outing and allow the bag to air at room temperature.

As a side note, even the MTX Trunk Dry Bag’s side zippers will allow some water inside, given the right conditions. Talking of which, though the RX system is generally smooth, if you’re shunning mudguards, wet, gritty stuff can get trapped in the channels over time, making engagement and release a little fussy. Easily sorted by removing the bag when washing the bike and give the tray a soft brush tickling. The sensibly sized carry strap with broad shoulder pad means its comfortable and reasonably unobtrusive to wear when mooching about. The carry handle is similarly practical for shorter periods and a godsend if you’ve left the shoulder strap behind.

Durability/Care 3.5/5

Ours is faring very well, despite regular exposure to frisky foliage aboard Ursula and my gravel bike. Not so much as a loose thread. The DWR coating also seems unaffected by this, heavy rain and scuzzy stuff thrown up along unmade roads. I’ve deliberately allowed this to accumulate and turn slightly crusty before washing it down. I’d never toss it in the machine, opting for a few liberal blasts of bike wash, warm water, lathered up with a medium soft brush.

Most grot slithered away with modest effort and in a matter of minutes. Remove any tooling, spare chain links and other stuff that could turn rusty and allow to dry. The fabric and zippers are water resistant, not impervious. Zippers can also be a weak spot, but these and their tags feel suitably robust and tolerant of the inevitable, everyday accidental carelessness. As for the rack, well the finish is holding out very nicely and a light drop of oil in the recessed bolt heads has kept taint at bay.

Value 3.5/5

£66 is reasonable, given the specification and standard of detailing employed. It’s worth noting that the RX Trunk Bag is designed to overcome the specific problem of carrying moderate amounts of kit on bikes where other forms of rack are impractical, or possibly undesirable. If you were looking to do weekend, or longer tours on a budget and were happy to attach a 4 point rack more permanently, possibly using P clips on frame-sets without eyelets, then a pairing such as this Oxford HD Alloy Luggage Rack and these Lomo Zephyr Waterproof Panniers could be the most cost effective option.

There are other options, if you’re averse to racks full stop and run metal seat posts. First up, there’s Carradice’s SQR system. Their Carradry SQR Bag (£83.94 presently reduced to £69.95) has 18 litre carrying capacity, is made in the UK from waterproof TPU coated polyester, has a ten kilo maximum payload and comes complete with lifetime warrantee.

Ours is still in rude health several years and many thousand miles down the line. Tipping the scales at 1390g empty and despite considerable charm, it can be a bit of handful when heavily laden. It also consumes quite a bit of seat post, which could also prove a deal-breaker, especially for smaller riders. Axiom Ocean X Post pack is another system that might appeal $199 Canadian dollars (£110) it’s very slightly cheaper than buying the Topeak RX Trunk Bag and Topeak RX Beam Rack as a pairing. It’s also a little sleeker, employing its own integral frame for support and stiffness. Maximum capacity is 12 litres, but there’s no padding and maximum carrying capacity is 3 kilos and while fond of the SQR post mount, it’s not suitable for everyone, or every bike.

Ortlieb Quick Rack (£100 rrp) is a little trickier to set up than the Topeak, but will manage 15 kilos and traditional panniers, so might be a better choice for those not wanting to be subscribed to a particular system. In terms of strictly trunk bags, Carradice Super C rack bag will swallow thirteen litres, is made from waterproof cotton duck and a universal fit, thanks to the Velcro straps. Mine’s still going strong, thirteen years down the line. However, it’s also a bit dearer at £89.99. Blackburn also produces a beam rack, the Central which retails at £59.99 boasts a four-bolt post clamp and a claimed 10 kilo maximum carrying capacity. It’s not a system rack as such as there’s no pannier side rails, but supposedly universal in terms of trunk bag attachment.

Summary

The shorthand version is the Topeak RX Trunk Bag DXP delivers on the design brief well and is one effective solution for road bikes without rack mounts. I believe it represents best value if you were already running a Topeak rack, such as the Uni Super Tourist 2.0 Non-Disc Rack (or its disc specific stablemate) on a tourer or mountain bike and wanted to be able to port the bag between them and a pared to the essentials bike for fast day rides. That aside, it is also a unique design, setting it apart from other beam types, which is another definite plus. That said, those wedded to carbon posts will need to look elsewhere.

Verdict: 3.5/5 Nicely executed system with wider scope than riders looking to expand carrying horizons of minimalist bikes

Michael Stenning

PUBLISHED MARCH 2026

Topeak RX Trunk Bag DXP 808g £66 & Topeak RX Beam Rack 665g £59.99