Have an old bike combination lock that you can't remember the code for? If it's a simply four-digit cable lock, you can easily figure out the combination with a quick peck-and-go method. Best of all, this technique doesn't require any tools or special know-how, and let's you reuse the cable lock again versus just damaging it with bolt cutters. All you need is a bit of patience and you'll have your figure out your combo in no time.
Also, it should also go without saying—don't be a jerk and use this to steal bikes. And if it's this easy to crack a rotary bicycle lock, then maybe you should just upgrade to a stronger lock anyway (remember your code or key this time).
Get all of the same digits to line up at the starting position. You can start with any digits, but it just makes sense to start at 1. The method here is to tug at each end until you see a gap form. For example, when the first number has the correct digit, you'll notice a small gap between the first and second slots.
As you can see below, once the first number reaches 3, you can notice a small gap when tugging at each end. This means we have our first combination digit.
Go down the line until you each the final number. Here, when you get the correct digit and pull on each end, your lock will open up. Pretty simple, right?
For more information, check out the full video guide below from YouTube user diilonp23. While this is not guaranteed to work on all combination cable locks for bicycles, since designs are all slightly different from manufacturer to manufacturer. But who knows, you might get lucky and save your lock from bolt cutters.