A good bike lock prevents theft by a potential bike thief. What sounds so simple and succinct, we would like to shed some light on. There is no such thing as "the good bicycle lock" and there is no such thing as "the potential bicycle thief". The market offers a wide range of different bike locks that are just waiting to be allowed to protect a variety of different bikes and e-bikes.
The reasons why exactly this bicycle was stolen in that place can also be manifold. Was it a spontaneous idea to simply get from A to B with the unlocked bicycle that was leaning against the wall of the house in the pedestrian zone? More of a "borrowing" because it was parked again 2 km away? In this case, a simple spiral lock would probably have been sufficient, as the thief would not have bothered to pick a lock. But no matter what the motivation behind a bicycle theft is. It is always very unpleasant for the owner when his bike is suddenly gone. Anger, helplessness and even fear come over a person who has been robbed. It is always an invasion of one's privacy, even if it is "only" a bicycle.
That is why we would like to give a few tips. In general, the heavier and bigger a lock is, the more it deters a thief from trying to pick it. A theft should always be quick, inconspicuous and quiet. There is a rule of thumb to spend about 10% of the value of the bicycle on a lock. We consider this rule of thumb to be outdated, because there are now very good quality bicycle locks for less than 100 euros that are extremely secure and also quite sufficient for an e-bike worth 3,000 euros. Insurance companies also state a purchase price of at least 50 euros for a lock in order to consider the bicycle sufficiently secured. This can be a good spiral lock, a spiral armoured lock or a folding lock, for example. The spiral locks are very popular because they are very easy to handle and do not get in the way when placed around the seat post and frame while riding. Folding locks have been very popular for some time. Firstly, they are very difficult to pick, especially if they are large and heavy. Secondly, they usually come with an attachment that is simply screwed to the frame. There, the lock can be disengaged and re-engaged with a short click. So it's very quick to use and easy to keep safe while riding.
No matter which lock you choose, there are still more measures to protect your "sanctuary". Don't leave your bike in a secluded alley where there is hardly any public traffic. Most of the time, such alleys are not very well lit at night. So the thief does not have to fear being caught. For most owners, a very expensive bicycle is more of a piece of sports equipment anyway, which goes straight back into the garage or cellar after the tour. By the way, the following also applies here: always lock the bicycle, otherwise the household insurance or bicycle insurance will not cover the theft. It is better to take your older bike for the purchase, which is not so conspicuous and does not motivate a potential thief to see it as valuable stolen goods that he can quickly turn into money again.