If you have a helmet lock on the side of your bike, you can easily make a tool that will enable you to lock two helmets. Go to the hardware store and buy a couple of feet of 1/8 inch stranded cable along with a 2 pack of crimpers.
Make a small loop on each end and crimp with a ball peen hammer so that the entire length is about 10 or 11 inches. Before you make the second loop, slide a clear, 3/16 I.D. plastic hose over the portion between the first and second loop.
You can then run the cable between the rings or 2 helmets and hook both loops into the helmet holder. You can make this little rig in about 10 minutes and it will cost about $2.50. By the way, even though 1/8 strand cable is pretty thin, it's really hard to cut through without a bolt cutter. Also, when it's not in use, you can leave it in the helmet holder and it won't get in the way at all.:-D
Make a small loop on each end and crimp with a ball peen hammer so that the entire length is about 10 or 11 inches. Before you make the second loop, slide a clear, 3/16 I.D. plastic hose over the portion between the first and second loop.
You can then run the cable between the rings or 2 helmets and hook both loops into the helmet holder. You can make this little rig in about 10 minutes and it will cost about $2.50. By the way, even though 1/8 strand cable is pretty thin, it's really hard to cut through without a bolt cutter. Also, when it's not in use, you can leave it in the helmet holder and it won't get in the way at all.:-D