A disk lock might encourage the casual thief, if alarmed it might attract enough attention to prevent a theft.
On the plus side, your insurance premium might be reduced as a result of the added precaution.
On the funny side, if using one of these devices, make sure you put it on the right way round.
I had been using an alarmed lock (125decibels) for a couple of weeks when I inadvertantly put it on with the keyhole facing the wheel.
With the solid rear wheel on the Sporty I had no way to use the key.
It took me a couple of minutes to remove the batteries to silence the thing screaming in my ear and twenty minutes with an angle grinder
to cut it off without damaging the bike.
Doh!
Another priceless forum lesson - thanks for sharing!
