Acros Block Lock is a headset with a feature to restrict the turning circle. It’s just the top part of the headset, which reduces fitting costs and expense.

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We’ve started seeing a few issues on modern trail bikes, and e-bikes in particular, where the bars swing round and the shifter or dropper remote gouges a big groove into the top tube. It’s due to a combination of things – low rise handlebars, stubby stems and bigger frames. To address the problem bike manufacturers have come up with two solutions – limit stops built into the frame, like Trek and Canyon, or a custom headset with a feature to restrict the turning circle. Both work in the same way the headset option is the most versatile because it can be fitted to any frame. The Acros Block Lock headset is an example latter.

To limit bar rotation, there is a tab CNC machined in the Acros aluminium cup and this slides in a groove machined in the top cap – when it gets to the end of the groove it stops. Overall steering angle is limited 164degrees, which means if you set the mechanism centrally, it stops 13-degrees either side of the top tube.

I fitted the Block Lock about six months ago. Fitting is pretty straight forward, although the top cap did work loose after one ride so it’s definitely worth checking tightness early on.

At £65 for what is effectively half a headset, the Block Lock isn’t cheap, especially when you can buy a full Hope headset for only a fiver more but it does have, double sealed, angular contact bearings and is currently the only after-market solution, apart from some pipe lagging and a bit of tape, to stop the handlebar bashing into your top tube.