Of the many options to carry extras on your bike, a top tube bag is one of the smallest but most useful.
Perched on top of your top tube, usually at its front end, these bags are easy to access, although the available capacity is usually only between half a litre and two litres.
Their position makes top tube bags a natural place for food, a phone and small items you need to access quickly when riding. This leads to their other name, bento boxes, the Japanese term for a single-portion packed meal.
Here, we’ll look at why you might want to add a top tube bag to your bike and what to look for in a top tube bag, as well as how they can augment other bike bags to provide a little extra storage on your rides.
Who uses top tube bags and why?
A top tube bag or box is handy to access while riding and you can easily see what’s inside. That makes it a great place to store food, but you can just as easily use these bags for other items you want handy, such as a phone, tools or a spare inner tube.
The additional storage helps free up or augment capacity in jersey pockets or enables a triathlete to wear a pocketless tri suit – or a time trialler to wear a skinsuit – while still carrying on-bike nutrition.
The ease of access makes a top tube bag a natural addition to a bikepacking setup, adding extra load-carrying capacity. Bolts for a top tube bag are pretty much standard issue on gravel bikes.
Many endurance road bikes, such as the BMC Roadmachine and Cannondale Synapse, also come with mounting bolts for a top tube bag, enabling you to carry more on longer rides, audaxes or in races.
What to look for in a top tube bag
Capacity
The key consideration with any top tube bag is how much capacity it will provide. While some top tube bags can swallow around two litres of gear, most are smaller. They typically have up to one litre of volume.
Consider what you might want to use a top tube bag for and decide how large yours needs to be.
Width
Top tube bags are usually narrow. This limits their capacity, but stops them from getting in the way. Nevertheless, a top tube bag may rub against your legs, possibly while riding seated.
You may rub against the bag when riding or climbing out of the saddle, so check that you’re comfortable with your top tube bag fitted.
Top tube bag straps and fixing
Your top tube bag needs to be fixed to your frame so it can’t move or flop around. If your bike frame includes bolts at the front of the top tube so you can screw your bag in place, then a bag designed to be screwed down is useful.
If your bike doesn’t have mounting points, try a top tube bag with straps that go around the tube. These may be made of Velcro, but make sure they’re either rubber-backed or made of soft materials to avoid scratching your bike’s paint. Rubber straps are a better solution. Even so, add frame protection strips to the top tube to avoid any scratching.
There’s usually a strap or bungee to fit around the bike’s headset spacers, below the stem, to help stabilise the bag.
Materials
Top tube bags usually have quite rigid sides to help stop them from bulging and the fabric is usually weatherproof. They may be made of abrasion-resistant fabrics to avoid wear from knee rub. Some are rigid-sided to ensure they remain tucked away behind the headset out of the wind.
There may be padding inside to stop items rattling against your frame.
Weatherproofing
As with any bike bags, keeping out water and muck is important. Most top tube bags will have waterproof zips and be made of weather-resistant fabrics.
Some bags have a cable port, so you can carry a USB powerpack and link it to bike lights or a cycling computer.
Internal organisation
Top tube bags often feature internal organisation. This can be handy to keep food away from tools.
Internal dividers can make it awkward to carry some items, so check they don't interfere with what you intend to carry.
Some internal dividers are removable.
Location
Top tube bags are typically designed to mount at the front of the top tube. But you can also buy top tube bags that mount at the rear of the tube, with a strap to hold them in place on the seat tube. You can often fit a front bag with strap mounts at the back, too.
While a rear bag can add some handy extra capacity, check you’ve got enough seatpost extension for the bag to fit – and there’s even more potential for rubbing than with a front top tube bag.
Other ways to carry your belongings while cycling
Top tube bags are among the suite of bikepacking bags you can use to carry your load when going on a gravel riding or road touring expedition. Pair your top tube bag with a large-capacity saddle bag, a bar bag and a frame bag, or a selection of these, and you can tailor the carrying capacity you need to the length of trip you’re planning.
Alternatives for carrying include a rack and either panniers or a rack bag. They’re classic solutions for carrying stuff on a touring bike, but while these provide plenty of stowage room, they lack the easy access of a top tube bag.
A backpack is another solution for carrying things. Popular with commuters and urban riders, a backpack provides a decent amount of capacity and has the advantage that you can carry it with you when you stop riding. On the downside, it puts weight on your back and shoulders, raises your centre of gravity, may hinder your rearward vision and is difficult or impossible to access when riding.
Triathletes typically have additional stowage in a frame box or behind their seatpost, both of which are usually designed to improve the aerodynamics of their tri bike – although such solutions are often banned from time trial bikes.
Endurance and gravel bikes, such as the Trek Domane, higher-spec Canyon Endurace models and the ENVE Fray, now often incorporate in-frame storage. It’s commonly used for tools, freeing up capacity in pockets for more food for your ride, although it can be a handy place for an emergency energy gel, too.
