Trying to fit everything you need for a two week tour into your panniers can be a challenge, particularly if the climate is such that a few bulky sweaters and fleeces will be needed. So, when I saw something described as a travel vacuum bag when browsing in Tescos, I thought I'd give it a try. For £5 I got two 55 x 40 cm (21" x 15") bags, weighing about 100g (4 oz) each. They work on the same principle as those under-bed storage bags that you fill with bedding and then connect to a vacuum cleaner to suck the air out, producing a much slimmer pack than would otherwise be the case, but no vacuum cleaner (or any other kind of extraction device) is needed, not even a bicycle pump.
I filled a bag with a pile of neatly folded T-shirts plus a heavy fleece and a lightweight jumper, squeezing in as much as possible while keeping everything flat. Then, following the instructions, I pulled on the flaps attached to the ends of the large blue opening to stretch out the upper and lower layers of the opening and make them lie smoothly one on top of the other. The blue plastic readily sticks to itself, so it didn't take much effort to smooth the layers with my hands and get them to seal. The instructions advise rubbing with a cloth to remove all the creases, but this wasn't really necessary.
The next stage was to start rolling up the bag from the opening edge. Once you start rolling, there is no way the opening is going to spring open again. At the same time, I encouraged the small tubular opening at the other end to open, as I was concerned I might burst the bag otherwise, but it tends to open of its own accord anyway to let the air out as you start to roll (or just squash) the bag to remove the air. Whether you decide to roll or squash will depend on the space available in your pannier and how bothered you are about creasing your clothes — rolling probably introduces more creases but makes for a smaller package. A second person is useful if you decide to use the squashing technique, or you can just just sit on the bag. I would recommend rolling the opening edge a little anyway, even if you then squash, just to make sure it doesn't come undone.
Once you have got out as much air as you feel is sensible, smooth the top and bottom of the blue tube together to seal it and stop the air getting back in, and then you can release the pressure. The bag will remain more or less the same size and shape as it was and will now be too stiff to bend much, so make sure it is the shape you want it (eg curved a little to follow the outside of your pannier) before you seal the tube. You should now have a bag that is somewhat smaller and denser than when you filled it.
← before squashing the air out
after removing the air→
The instructions that came with the bags seemed quite complicated, but actually the whole process was very intuitive and having done it once I certainly won't need to read the instructions again. Packing two bags probably took 3 minutes at most.
I used the bags, one in each pannier, on a recent trip and found them worthwhile. Cycling in spring or autumn means being prepared for cool mornings and evenings, and using these vacuum bags allowed me to pack a heavy fleece that would normally have been held on my pannier rack with a bungee or tied round my waist when not being worn. I was also able to take a couple of extra long sleeved tops for wearing on cooler days. At the end of the trip when everything in my panniers was dirty, stuffing each vacuum bag full of dirty clothes meant they took up the minimum of space despite not being neatly folded. Of course, my panniers were a shade heavier than they would otherwise have been, but that only matters if you are going to be doing a lot of uphill cycling — which I wasn't.
Another thought that occurred to me is that anything stored in a vacuum bag is bug-proof (assuming the bugs don't munch their way in through the plastic), so they would be a good idea if you were travelling anywhere hot and damp where creepy-crawlies are commonplace. You could leave clean clothes in a vacuum bag overnight in your accommodation and be reasonably confident that they would still be clean, dry and insect-free in the morning, no matter how insalubrious the surroundings.
In conclusion, these bags are a cheap solution to the dilemma of what to leave behind when packing for a cycling holiday. As long as you don't mind carrying a little extra weight, they are a useful addition to a touring cyclist's kit.
Zipped holdall (aka Karachi suitcase)
I don't know what the proper name is for the ubiquitous, cheap-as-chips, gussetted, tartan bags that are popular with tramps, budget travellers and students, but I have heard them called Karachi suitcases. They are made of woven plastic and have a zip along the top and carrying handles. They come in several sizes and can be found for sale on market stalls and in cheap shops all over the world. I often fly with my bike and several panniers, and even non-budget airlines usually charge for each checked-in item nowadays while all airlines strictly limit cabin baggage to one item. So I thought I'd give a Karachi suitcase a go on my last trip, to make three panniers magically become one item of luggage. For some time I've been putting my panniers into a single black dustbin bag at check-in and sealing it with parcel tape, but I'm aware that some airlines don't allow this. Their objections are on the grounds that the package cannot undergo a security inspection without ripping the bag, which means it cannot be repacked afterwards and the individual panniers will then be in the system without luggage labels. I knew that, sooner or later, I'd be stopped at check-in and made to pay an extortionate fee for the extra, non pre-booked, items of luggage.
I bought my Karachi suitcase from a shop of the cheap-and-cheerful variety in my local town. They were just labelled "multi purpose bag" and there were 4 sizes available, from small to extra large. Even the largest "super jumbo" version, measuring 39"x30"x14" (99cm x 76cm x 35.5cm), cost only £1.99. It seemed so large that I did wonder whether it might take my bike (with the wheels removed), so I bought one to find out. But it didn't come close to fitting in. It's a shame that there doesn't seem to be a size above "super jumbo" that would hold a bike, since so many airlines now insist that they travel in some sort of bag or box. But I digress. Realising that a smaller size would solve my pannier problem, I went back and got a medium bag measuring 22" x 19" x 11" (56cm x 48.5cm x 28cm).
A bit of experimentation revealed that the Karachi suitcase would roll up quite small (see photo right) and it only weighs about 7oz (200g). In this form, with a bungee around it, it tucked under the back of my saddle and I pretty much forgot it was there for the duration of a fortnight's tour in Germany. In use, it snugly held three panniers of about 22 litres capacity each. (56cm x 48.5cm x 28cm gives a total capacity of 76 litres, but panniers are, of course, not neat cuboid shapes that fit together easily.)
I was really pleased with this as a money-saving answer to airline baggage fees. Multiple panniers are not normally the easiest of things to carry once they are off the bike, but the Karachi suitcase's handles meant that it was easily lifted on and off baggage trolleys and the belt at the check-in desk. The photo shows my loaded trolley, complete with two bagged bikes.
I can see other situations on cycle tours where it would be useful too, like carrying panniers and other paraphernalia up to my cabin when taking the bike on an overnight ferry, and taking dirty washing to the laundrette mid tour. If you have a lot of bicycle packaging materials (a CTC polythene bag or a cardboard bike box, foam pipe insulation, bubble wrap, tape, etc) and you have made arrangements to leave it at an airport hotel until your return journey, then you could stuff it all in your Karachi suitcase. But if you have to carry all your packing with you and the extra weight of a Karachi suitcase bothers you, then throw it away at the arrival airport and buy a replacement at the end of your holiday, it will be a lot cheaper than paying for even one extra checked-in pannier.