The short version: buy a hardened U-lock (or a heavy folding lock), spend a bit more than feels comfortable, and learn to lock the frame and a wheel to something immovable. The lock matters less than how you use it.
Lock types, fastest to most secure
Cable locks look like security and aren’t. Bolt cutters or even strong snips go through most of them in seconds. Treat a cable as a way to tie down a wheel or a saddle, never as your main lock.
U-locks (D-locks) are the standard for good reason: a hardened steel shackle resists bolt cutters and leverage far better than a chain of the same weight. Smaller is stronger — a compact U-lock leaves less room for a thief to get a tool inside.
Folding locks trade a little security for a lot of convenience: they pack down small and carry easily, and the good ones are genuinely tough. A sensible middle ground for everyday riding.
Chains can be very secure, but only thick, hardened ones — and they’re heavy. Worth it for a bike that lives outside or in a shared space, less so for daily carrying.
What “secure enough” means
Don’t judge a lock by its marketing. Look for an independent security rating: in the UK, Sold Secure (Bronze, Silver, Gold, Diamond); in the Netherlands, ART. These bodies actually attack the locks. A higher rating means more time and noise to defeat — which is the whole game, since a thief wants neither.
A rough rule of thumb: spend around 10–20% of the bike’s value on locking. On an e-bike or anything expensive, go up a tier, and consider two different locks (a U-lock plus a folding lock or chain) so a thief needs two different tools.
How to lock it (this matters more than the lock)
- Lock to something fixed and solid — a proper bike rack bolted to the ground, not a flimsy sign or a post the bike can be lifted over.
- Put the U-lock through the frame and the rear wheel, around the rack. The rear wheel is the expensive one.
- Fill the space inside a U-lock with bike and rack so there’s no room for a tool. Less air, more security.
- If your front wheel or saddle is quick-release, take it with you or secure it with a cable or a second lock.
- Point the keyhole down or inward so it’s harder to attack, and lock the bike where it’s busy and well-lit.
A few honest cautions
- No lock is unbeatable — the goal is to be slower and louder to steal than the next bike. A thief with time and the right tool will win; your job is to not be the easy target.
- A cheap lock on an expensive bike is a false economy, and so is a great lock used badly.
- Register your bike’s serial number and photograph it. It won’t stop a theft, but it helps recovery and insurance.
This guide covers durable, well-established lock advice; the security-rating schemes named (Sold Secure, ART) are independent testing bodies you can verify directly.