How to choose a chain, and how to carry one
Start with where the bike sleeps. If it lives outside a station or on the street overnight, a 14mm hardened chain rated 10/10 is the pick — and the smart move is to leave it locked at that spot so you never carry the weight. If your parking is daily but not overnight, a 10mm mid-weight chain like the Evolution gives real deterrence at a weight you can actually sling in a bag. And if you hate carrying a chain at all, a wearable design rides the load on your hips instead of your shoulders — a clever answer for commuters who want chain-level security without the backpack.
Length is the other lever. More reach lets you lock to distant or fat racks and secure two bikes, but every extra foot adds weight, so buy the reach you need and no more. Whatever chain you choose, thread it through the frame and rear wheel and around something solid and immovable, kept up off the ground so a thief can’t use the pavement as an anvil — the technique in how to lock your bike applies to chains as much as U-locks. For a heavy, valuable bike, pair the chain with the wider plan in the best e-bike locks, and if you’re wondering whether to go all the way to a grinder-resistant lock, we weigh that in are grinder-proof locks worth it.
Reach is also what makes a chain the only practical tool for securing two bikes with one lock — how to lock two bikes together covers the length you need and how to route it so a bar cannot be used for leverage.