The Ionus chain lock is a newly updated version of the Abus Steel-O-Chain, which has been rated pretty highly by us in the past. It differs from that model in that the lock mechanism now has a larger square shield.
Inside the new plastic cover is the same clever bolt mechanism, which is ﬁxed to the chain with a 3mm steel armoured case. But, cleverly, both the lock and bolt – at the chain’s other end – are ﬁxed but still allowed to rotate.
This makes it extremely difﬁcult to attack what’s usually the most vulnerable part of this style of lock because levering is made tricky thanks to the freely rotating parts.
In our ﬁrst test the chain was very resilient to cropping; we dented the links without actually cutting them. Attacking the lock mechanism with hammers and chisels for ﬁve minutes created a lot of cosmetic damage but the lock maintained its integrity.
In test two we had power tools on tap and cut through the chain in a little over 30 seconds. Overall, though, this is one of the most portable chains available and is tough to boot. The Ionus comes with two keys.