A published certification. Insurers’ organisations test locks by attacking them with named tools for a named duration, and a lock carrying one of their ratings has been through that. A lock quoting only a link diameter has been tested by nobody.
Why diameter is a poor guide
A thick link of soft steel is cut faster than a thinner one of hardened steel. Hardening is published where it exists, and it changes the outcome more than millimetres do — which is why the specification that matters is the test result rather than the measurement.
What the certification actually records
An attack, with a defined set of tools, for a defined time, by people whose job is to open it. The rating is the level at which it held. It is a real, repeatable measurement, and — like every other marking on this site — it describes a test rather than promising an outcome.
The part that decides more than the lock
What it is fastened to. A chain around a wheel is a chain that leaves with the motorcycle. A ground anchor or a wall anchor turns the lock into security; without one, the best chain on the market secures the machine to itself. This is why anchors belong in the same conversation rather than in a footnote.
What each type does and does not do
A disc lock prevents the machine being ridden away and does nothing to prevent it being lifted into a van. A chain or a U-lock through the frame to an anchor addresses the second. An alarm adds noise and attention. They are layers, and each one is honest about which layer it is.
The figure that decides whether it is used
Weight. A heavy chain stays at home and a light one is carried, and the best lock for a rider who commutes is often not the heaviest one. A lock in a garage secures nothing.
Questions riders send in about this
Is one good lock better than two ordinary ones?
They do different jobs — one prevents riding away, another resists being cut. What is published is what each was tested against, and the layers are not substitutes.
Do insurers require a particular rating?
Some policies specify one. That is a question for the policy document, which states it, rather than for a comparison page.
Last reviewed 18 September 2026