Snow chains are a safety device made up of several sections of metal chain and fitted around the tyres of your Smart. They significantly improve the grip and traction of your Smart on snowy roads.
Having a pair of snow chains or socks on your Smart is essential for driving in areas with a reputation for snow (e.g. mountains, ski resorts). Also, the snow tyres fitted to your Smart may not be sufficient, especially if the famous B26 sign is present, making it compulsory to fit snow chains or snow socks approved to B26 (yes, that's right) on at least two driven wheels.
The obligation to use Smart car chains ends at sign B44 (it's sign B26 but with a nice red diagonal bar).
Some Smart tyre chains are said to be "unchainable" because the wheel arches are too narrow. This does not mean that you cannot fit a snow chain, but these will be specially designed for a particular chain system called "NO INSIDE CHANNEL".
Note: the manufacturer Smart declares some of their vehicles as "non-chainable" for reasons of space: the space between the tyre and the vehicle fender is too narrow or the presence of equipment on the tyre (e.g. pressure sensors) hinders the installation of a car sock.
According to the Loi Montagne (see map of France of the departments concerned), from 1st November to 31st March, it is necessary to have at least one piece of winter equipment compatible with the Loi Montagne (either snow tyres or approved car chains or snow tyre socks) in order to be able to drive, on pain of a fine. Two new signs have been created, B58 and B59, to indicate the beginning and end of the zones concerned.
Please note: the adoption of the new B58 and B59 signs does not mean that the old B26 and B44 signs, which may still be in use, have been removed. Therefore, it is important to understand that if snow tyres are sufficient for the Mountain Law, they will not be sufficient if the B26 sign is present, which makes it compulsory to have approved snow chains (or tyre socks) on your Smart. In other words, a word of advice: think ahead and have your snow chains in your Smart just in case, when you travel in the departments affected by the Mountain Law.
As mentioned above, car chains must be mounted on the drive wheels. As you know, a car is either front-wheel drive (front wheels are driven), rear-wheel drive (rear wheels are driven; very sensitive to slippery roads) or four-wheel drive (also called all-wheel drive, e.g. 4matic system at Mercedes, Quattro at Smart, 4motion at Volkswagen, Xdrive at BMW). In the special case of rear-wheel drive, it is still recommended that all four wheels (vs. only the rear drive wheels) be equipped with tyre chains. This is also the case for four-wheel drive, in particular for a better distribution of traction.
Better than a long speech, here is a video example of ultra fast snow chains (see video). As you can see, heavy chains can be complicated to assemble if it is your first time. As our colleagues at Techniques-pilotage.fr (https://techniques-pilotage.fr/prevention-hiver) say so well, the difficulty of assembly increases with stress, cold, snow and low light. We therefore recommend that you train beforehand: in dry conditions at home, before leaving on holiday.
It is usually necessary to stop and re-tension the chains after mounting and driving a few kilometres, especially if your chains are "manually tensioned". On the other hand, automatic snow chains are self-tensioning (i.e., wonderful, it's automatic!): no need to stop. You just get on and drive. It's a bit more expensive but so practical, isn't it ?
With or without snow chains, driving on snow requires a "cool" driving style. You must avoid sudden braking and acceleration with your Smart.
When the road is no longer snow-covered, remember to remove the chains from your Smart because it is then forbidden to drive with them.
If you want to go far, take care of your mount: after each use, clean the snow tyre chains properly and dry them well before storing them.