Panniers are great for heavy loads and long-distance commuting, but if you're popping out to the shops, hauling a laptop or snipping in and out of traffic, a messenger bag or rucksack is just the ticket.
What's more, a light cargo on your back keeps your bike's handling razor sharp and when it comes to that last minute dash for the train it's far easier to shoulder an unladen bike up a flight of stairs. If you regularly commute by bike, a good pack is essential.
Style aside, which bag is best for when? Look around any big city and you'll see messenger bags offer quick and easy access on short-hop rides. They offer good visibility over the shoulder too and their shape makes them great for carting books, documents and clothes around. On the other hand, rucksacks distribute weight more evenly, so if you're prone to suffering a sore back, we'd suggest keeping your freight across two shoulders. You'll need to drink on long commutes, so most feature integrated hydration systems or options. Here's a rundown on what to look out for...
A padded shoulder stops the strap from digging in when the pack's loaded up.
The best packs can be adjusted quickly with a buckle. Cinch it in when you're riding, and loosen it off when you need to pull something out - though smaller riders may need to cut down the excess strap.
The stabilising strap keeps the bag from swinging round when riding, and differentiates bike bags from high street models. Some can be fitted to either side, enabling you to change shoulders
Check for reflectors and light hoops, and where they sit in relation to your riding position. depending on your preference.
The main compartment generally features an array of pockets and dividers for tools or wallet, and a laptop sleeve. An easy to access external compartment is useful for your bike lock or house keys.
A tough Cordura-like material will shrug off day-to-day abuse, while a waterproof lining keeps your paperwork bone try. Check that the corners overlap and are watertight too.
Big velcro patches are handy if you're in a hurry, with buckles to keep larger loads more secure.
Male and female designs vary in the shape of the harness. Sternum straps help spread the load; the best are adjustable and even removable.
Most packs offer a port for a hydration system. If you're going to use a bladder, make sure you keep it clean and avoid sugary drinks
Some hip belts can be tucked out of the way when you're off the bike.
A carry handle is surprisingly useful and great for hanging the pack up.
Some backs use a suspended harness to keep sweat at bay; others use panels to channel air. Check for adjustability too.
Reflective piping and panels are a must if commuting at night, as is a loop for an LED light.
Bungees and mesh pockets are great for gear overflow and make for quick access.
Many packs are expandable. Compression straps keep the pack stable, even if it's half full.
Ports and padded pouches for MP3 players and helmet light batteries are popular these days.
A high-vis rain cover is a sensible UK feature - or line your bag with a thin watertight canoe bag (eg Exped).
Tips for sizing
Rucksacks and messenger bags come in all shapes and sizes, with each brand often offering a variety of options. Be realistic with what you need, or the temptation is to over-pack and lug too much around. If you can, try on messenger bags when fully packed, so you can check visibility over your shoulder and ease of access. With rucksacks, put your helmet on and adopt a riding position to see if your head clips the top of the bag. Some models have shorter backs, and are best suited to smaller riders. Dedicated women's models have differently shaped harnesses too.