Best top tube bags for triathletes

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

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%

Zefal Z Aero

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%

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%

Altura Vortex 2 Top Tube Pack

Both top tube bags on test would easily be at home in a bikepacking set-up, such is their capacity.

Altura doesn’t quote the exact volume of their Vortex 2, but we’d put it at slightly over a litre, so you could easily fit around a dozen gels and a mini pump in there, or a mix of gels, bars, pump, inner tube and tools. Ideal for lengthy training rides or long-distance tri’s.

The bag is attached to the top tube via three Velcro-style straps (two at the bottom, one at the front).

This achieves a reasonably secure fit, but through months of testing we did sometimes find the bag would lean to one side.

The thinner your top tube and heavier the bag, the more unstable you’ll find it, and this is where top tube bags attached by bolts can win out (Altura also offers a bolt-on version).

While cycling, our legs would also occasionally rub against the straps, though this wasn’t particularly common.

With an IPX6 rating, the bag is waterproof, a claim that was repeatedly proven on many a soggy summer ride.

The zip is also easy to operate, even on the fly, though it does need a bit of jostling if you pack it full. Some consumers have reported issues with the zip staying fastened, but we didn’t experience this.

Given its size, it’s unlikely to be the most aero, but if your headset’s pretty thick, it should tuck in nicely. 

Verdict: Roomy and reliable weather protection, but could be more secure.

Score: 82%

Apidura Expedition Top Tube Pack

Like several other options on test here, the Expedition Top Tube Pack uses Velcro-style straps to fit to the bike, though in this case there’s only one strap at the front and one below.

In practice, this didn’t seem to make it any less stable, but, admittedly, this is a slimmer product, so there was less of it overhanging our top tube.

Like the Altura, it would occasionally lean to one side, but not all that often. And, unlike the Altura, our knees rarely found it obtrusive, either.

It’s also not quite as tall, so there’ll be less protrusion above the bike’s headset. This, combined with the slimmer design, means we’d expect there to be less of an aerodynamic penalty, although this is purely anecdotal as we can’t back this up with data. 

There’s still one litre of space available and we had no issues storing multiple gels, a tool, phone and mini pump. Based on this, we’d say this is also a solid choice for long days in the saddle. 

The pack is also waterproof and, while the zip isn’t quite as easy to operate as the Altura option above, it’s still manageable while on the move.

Verdict: Slimline design makes this

Score: 85%

Lezyne Aero Energy Caddy

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%

What to look for in a top tube bag

When looking for a top tube bag for your bike, there are several important factors to consider. Here are the key aspects to look for:

Size and capacity

The size of the top tube bag will determine how much gear you can carry in it. Consider what items you plan to store in the bag, such as energy bars, energy gels, a multi-tool, spare tube, or other essentials.

Make sure the bag is large enough to accommodate your necessities without being too bulky or interfering with your riding.

Aerodynamics

An aerodynamic top tube bag can minimise wind resistance and reduce drag, which is especially crucial if you’re a performance-oriented cyclist or regularly ride at higher speeds.

Mounting system

It’s essential to choose a bag with a secure and stable mounting system to prevent unwanted movement during your rides. Common mounting options include straps with adjustable buckles or hook-and-loop closures.

However, some top tube bags can also be attached via bolt holes.

Accessibility

Easy access to your belongings while riding is crucial. Look for a top tube bag that has convenient zippers or closures that can be easily opened with one hand.

Waterproofing

Weather conditions can be unpredictable, and your gear may be exposed to rain or moisture.

Choosing a top tube bag with some level of waterproofing or water resistance will help keep your belongings dry and protected.

Durability

Look for bags made from durable materials like high-quality nylon or polyester. Reinforced seams and sturdy zippers contribute to the bag’s overall durability.

Overall, selecting the right top tube bag will depend on your specific needs and preferences, as well as the type of cycling you intend to do.

Looking for more ways to increase the storage space available on your bike? Check out our list of the best bikepacking bags.

Top image credit: Getty Images