Top tube bags, also called bento boxes, are small storage bags that are attached to, you guessed it, your bike’s top tube.
They’re handy for a variety of uses. In a race, your top tube bag will sit in prime reachable position, storing all your nutrition to fuel your bike leg and tools in case of emergency roadside repairs.
In training, you might opt for a top tube bag to stuff your valuables, phone, flapjacks and café-stop cash. They’re also popular in the bikepacking world, as they offer extra aero kit storage for cycling adventures.
In testing, we looked out for top-quality constructions with water-repellent and rigid materials, and also took into consideration which bags had both attachment options of bolt holes and straps.
Crucially, we tested the true capacity of each bag, including compartments and zip access, to decide just how well they weathered the gritty English roads. And here’s what we found…
Best top tube bags for triathletes
Topeak Fastfuel Tribox
!["Topeak]("https://images.immediate.co.uk/production/volatile/sites/34/2022/01/topeak-fastfuel-tribox-ac4024e.jpg?quality=90&resize=620%2C397" "\"topeak-fastfuel-tribox\"")
Compatible with triathlon or road bikes, Topeak’s Fastfuel Tribox can be strapped down or bolted onto bikes by using threads on the top tube. With a rubber opening instead of zip closure for quick access, you run cables through to the top tube for better aerodynamics.
A slimline design meant our inner thighs didn’t brush the box, even when climbing. Capacity-wise you’re slightly limited, we only got four 45g gel packs in laid down. But you could sit gels horizontally with the tops peeping out, which upped capacity to six.
You can also squeeze other small items like sweat salts to the sides of the main compartment. If you want aero top tube storage without buying a fully integrated superbike, this is a good investment.
Verdict: A premium aero top tube bag with just enough space.
Score: 83%
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Zefal Z Aero
!["Zefal]("https://images.immediate.co.uk/production/volatile/sites/34/2022/01/zefal-z-aero-top-tube-bag-18a974f-2.jpg?quality=90&resize=620%2C397" "\"zefal-z-aero-top-tube-bag\"")
Zefal’s no-nonsense Z Aero is water repellent, lightweight, and has a universal fit thanks to removal straps and bolt holes for mounting on compatible triathlon bikes. A 0.4L capacity translates to six gels at a push, with a tough zipper ensuring no rain, snow or debris gets inside when closed up.
The quite rigid polyester outer helps keep the bag secure and fixed in position when we use the straps to attach to our bike, and it’s slim so as not to compromise aerodynamics.
A handy pull tab makes it easy to open and close at speed, while no front strap means you can mount it anywhere on your top tube, and even use it in combination with a smaller pouch strapped to your headset in front of it.
Verdict: Affordable and versatile with a reasonable capacity.
Score: 80%
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XLab Stealth Pocket 100c
!["XLab]("https://images.immediate.co.uk/production/volatile/sites/34/2022/01/xlab-stealth-pocket-100c-0b3d61f-1.jpg?quality=90&resize=620%2C431" "\"xlab-stealth-pocket-100c\"")
XLab’s storage solutions have proved popular with triathletes for several years, particularly its super low-profile top tube bags. The ‘c’ in Stealth Pocket 100c stands for carbon, as the outer material has a cool ‘carbon look’.
Mounting with the three straps was a breeze, although there’s no option to mount using bolts. A large rubber zipper tab helps with opening/closing at speed, and the tough outer ensures the bag stands up to the elements.
Inside, a divider separates smaller items from larger nutrition products, which is practical unless you’re aiming for iron-distance and want extra capacity. We could only fit five gels in, so you might prefer the roomier Stealth Pocket 400 or 500.
Verdict: Not the roomiest, but functional and stylish.
Score: 78%
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Lezyne Aero Energy Caddy
!["lezyne-aero-energy-caddy-top-tube-bag"]("https://images.immediate.co.uk/production/volatile/sites/34/2022/01/lezyne-aero-energy-caddy-top-tube-bag-0b3d61f.jpg?quality=90&resize=620%2C431" "\"lezyne-aero-energy-caddy-top-tube-bag\"")
Lezyne was better known to us for its off-road and commuting storage solutions, but the Aero Energy Caddy is aimed squarely at ‘triathletes and gravel racers’.
With easily the largest capacity on test, nine gels fit in the main compartment, plus one more in the handy open side pocket that runs the full length of the bag; you could use this for any compact items that aren’t likely to go flying on precarious road surfaces.
Like the Topeak and Zefal, you can opt to bolt down the bag if your top tube has bolt threads, or use the sturdy straps underneath and on the front if not. Overall, the Aero Energy Caddy is a very useful storage option indeed, and it comfortably wins this grouptest.
Verdict: An ideal top tube bag that’s super sleek and practical.
Score: 90%
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Top image credit: Getty Images