The honest starting point for buying a bike lock is that no lock in this field survives an angle grinder. The strongest folding lock tested took about 44 seconds to cut through.
So the real question is not "is it unbreakable?" — it is how much effort, noise and time a thief must invest, and whether that is more than they are willing to spend on your bike.
How these locks were attacked
The testing is destructive and deliberately realistic. The tool kit is chosen to match what a thief would actually carry: a 61-centimetre bolt cutter — that specific length because it is the largest that still fits inside a big rucksack — a 25-centimetre side cutter for piano wire, a cordless angle grinder, and a cutter knife where relevant. Every attempt is timed and abandoned after 3 minutes at the latest.
Locks that survived and were candidates for the top spot were additionally examined in earlier rounds by experts from a lockpicking association, and some were attacked with a hand hacksaw — though neither is part of the standard procedure now.
Beyond brute force, build quality and equipment are assessed, because quality varies considerably across the field, and handling and weight are scored too, since a lock is only useful if it is convenient enough that you actually take it with you. Alarm models have their volume measured with a sound-level meter at one metre.
The lock types, and what each trades away
Folding locks are often assumed to be the weaker choice — and the field disproves that, while still calling them a compromise: more mobile than a chain, more compact than a D-lock, but not the equal of either on outright security. One folding lock in the field carries Art-3 certification, meaning it is rated secure enough for leaving scooters and e-bikes locked long-term — but it is also the heaviest of its category at two kilograms.
D-locks (U-locks) are the resistance benchmark: a solid steel shackle defeats even strong bolt cutters. The trade is bulk and rigidity, and shackle length limits what you can lock to.
Armoured cable locks buy flexibility and low weight, and defeat opportunists who carry a single tool — but they are not fully break-proof.
Chain locks offer length and, at the top end, extremely high resistance. They are heavy.
Alarm locks work on a different principle entirely: noise. They complement a physical lock rather than replacing it.
The picks
Best overall — Abus Bordo 6000K. The successor to a long-standing favourite, and the lock that overturns the assumption about folding designs: first-class build and exceptionally hard steel. Despite folding links only 5 mm thick — which says a great deal about the steel — it withstood attack for a long time. Against an angle grinder it lasted about 15 s, and while some locks buy a few seconds more, that is a strong showing for the format. Handling is good and the mount is genuinely well designed.
Best security for the money — Abus Granit XPlus 540. The choice for maximum security without maximum outlay: a massive steel shackle that resists even the strongest bolt cutters, and XPlus locking technology regarded among specialists as near-impossible to pick — picking an XPlus cylinder is far too time-consuming and complex to manage without specialist tools. It also holds up unusually well against an angle grinder: removing it from the bike completely took a full 126 s. The 30 cm version gives enough room to secure a bike to wide posts or lampposts. It has decent accessories and an automatic dust cover. The cost is weight — it is relatively heavy.
Best light and flexible — Abus Ivera Steel-O-Flex 7200. A genuine obstacle to opportunist thieves: without an extensive tool kit it is barely crackable, and a single tool will not get you far. It is not completely insurmountable, but the effort required means most thieves will not start. In exchange you get low weight, high flexibility and strong value. The honest debits: not fully break-proof, no dust cover, and sparse accessories.
Most secure — Seatylock Viking Gold 110. A very secure chain lock with details that separate it from rivals: despite the weight, a magnetic closure makes it pleasant to handle, and the massive chain links are protected by two textile sleeves. Hardened steel chain links mean bolt cutters get nowhere; realistically only an angle grinder opens it, and cutting a single link through took about 40 s. At roughly 2.8 kg it is no road-cyclist's choice, though it was not the heaviest model tested. That quality costs, in both money and weight.
Best alarm — Olympia S 200. Noise as a deterrent, and it commits: a siren reaching 90 dB, which should send most thieves running. Solid build and a low price make it a natural supplement to a physical lock rather than a substitute. Its limits are honest — only mediocre length, and somewhat rigid.
Also notable — Seatylock FoldyLock Elite. The only folding lock on the market with Art-3 certification, rated for leaving scooters and e-bikes locked long-term. Breaking it with brute force or bolt cutters looks unrealistic; an angle grinder took around 44 seconds. At two kilograms it is the heaviest of its category, and at 110 cm long enough for larger e-bikes. The build justifies the price — nothing rattles, the links run cleanly, the end piece clicks home securely, three keys are supplied, and registration with replacement-key ordering is offered. The maker does not claim it is angle-grinder-proof.
Also notable — Abus Bordo One 6000A. A solid folding lock available with or without a separate remote, with excellent app and remote control — the newer unified app added it in minutes and offers settings rivals lack, such as lock-tone volume and pre-alarm duration. Its alarm measures 85 dB at one metre, quieter than the dedicated alarm lock above but loud enough to deter a thief or draw attention. Two small gripes: the transition from links to sheathing could be cleaner, and the links do not always run smoothly, which occasionally makes locking up a test of patience.
Before you buy
Four questions. What is the realistic threat where you park? A bolt cutter that fits in a rucksack is the common tool; an angle grinder is a different level of determination. Will you actually carry it? Weight and mount quality decide that, and an unused lock protects nothing. How wide is what you lock to? Shackle and chain length settle whether a lamppost is an option. And is this the only lock? — an alarm complements a physical lock rather than replacing it, and two different lock types take two different tools to defeat.
Our best bike phone mounts guide covers the rest of the handlebar, and our best GPS trackers guide the recovery side if a bike does go missing.
Search current listings
Bike locks on Amazon UK | Amazon.com. Best overall: Abus Bordo 6000K on Amazon UK | Amazon.com. D-lock pick: Abus Granit XPlus 540 on Amazon UK | Amazon.com.
