The Birzman Belly S (for small) top tube bag provides a handy little spot on your top tube to stash a few gels or jelly babies if your ride planning somehow fails to include a cake stop.
Top tube bags are an alternative to the more commonly used saddle packs if you want to keep stuff handy to access while you're riding. They are used by triathletes in particular to facilitate the taking on of energy for those times when a cake-stop just won't fit in the schedule. Some people might find it surprising that cyclists plan a bike ride without allowing time for cake, but I have been assured that it happens.
If you've stuffed your gels in the saddle pack then you'll struggle to get at them without stopping, but with the Birzman Belly you can easily grab one even when you're hammering along. This also helps avoid annoying fumbling in jersey pockets trying to extricate the last unopened gel sachet from among the sticky empties. You do take your empties home, don't you?
A couple of Velcro straps attach to the steerer and the top tube - you won't want to attach it too tightly to the steerer for obvious reasons, but with the top-tube strap done up nice and tight it stays put reasonably well.
The Belly is available in a couple of sizes - this is the smaller one and it really is pretty small. Using the universal unit of measurement for such things, your reviewer can confirm it will accomodate a generoius handful of Bassett's Jelly Babies.
I found it would also take a handful of gels or a small multi-tool and some tyre levers - you'll struggle to get a phone, wallet or even spare tube in here. But you probably wouldn't really want to use it for a spare tube, as you don't generally need to get at these while you're riding. Energy gels or sweets are likely to be the main usage.
The bag itself has very limited protection from the elements. A simple Velcro flap covers the opening but not in a way that would really stop rain getting in - not a problem for gels though. It does come with an elasticated rain cover, but having to take this off makes access a bit less convenient. The absence of a zipped closure does mean that getting access is a piece of, well, cake - one-handed entry is very quick and easy.
The Belly is fairly aerodynamic, sitting quite neatly behind the steerer and hardly any wider. Some people might not like the look of this on a bike - it's certainly quite in your face when you're riding and might be thought to spoil the lines from the side too. That may the price you pay for not planning your ride correctly and allowing time for cake.
It has tiny pockets on the side which I've yet to find a use for. You could fit an aspirin in there but not a great deal more.
I can't currently find a single UK retailer selling this on the web, so you may struggle to find it. There are similar products available from a number of other manufacturers quite widely available, however.
Small, simple bag giving easy access to sweets and gels for those times when you just can't stop. Unlikely to improve the looks of your bike (but less obtrusive than some) - those concerned by such things will probably just keep using their jersey pockets.
road.cc test report
Make and model: Birzman Belly S Top Tube Bag
Size tested: Medium Black
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?
A midsize top tube bag designed for easy access of all necessities during a ride. Velcro top access for easy entry and reach of tools, energy bars, phone, money or any other small gear with rain cover.
I think "midsize" is over-stating it a bit, really.
Tell us some more about the technical aspects of the product?
Material: 300D*300D PU
Nothing fancy but it all seems well stitched together - should last a fair while.
Does its job well - holds securely in place and is easy to get into. Whether it's a job that you consider necessary is another matter.
Lightweight enough for what it is.
Comparable to similarly-sized top tube and saddle bags.
Tell us how the product performed overall when used for its designed purpose
For holding energy gels or other small items which don't mind the rain, the Belly bag makes it easy to get access while riding.
Tell us what you particularly liked about the product
Quick to put on the bike, quick to get into.
Tell us what you particularly disliked about the product
I'm not wild about how my bike looks with a top tube bag. That's a comment on top-tube bags in general rather than this one, which is perhaps neater than some of the competitors.
Would be improved if the Velcro flap was more weather-proof, thus removing the need for the rain cover.
Did you enjoy using the product? Not as much as I would enjoy stopping for cake.
Would you consider buying the product? Possibly, if I was planning long rides where I couldn't stop.
Would you recommend the product to a friend? Yes.
About the tester
I usually ride: Boardman CX team for the daily commute My best bike is: Rose Xeon CRS
I've been riding for: Over 20 years I ride: Most days I would class myself as: Expert
I regularly do the following types of riding: road racing, time trialling, commuting, touring, club rides, sportives, general fitness riding, fixed/singlespeed, mtb,