ive got a disc lock on mine, it really only stops thieves from rolling the bike away like the steering lock. an alarm is your best bet if you wanna get noticed

 

...or you could get both. Xena makes fancy disc locks with built in alarms. High dollar stuff, but they've worked great for me for years.

 

I've found out the hard way that alarms don't slow thieves down much. If you get an alarm, I'd recommend one with a isolated battery.

 

yup ive seen the disc locks with alarms, they dont seem that expensive, ones ive seen anyways. i just tend to not leave my bikes places where i cant see it. i wont bring it to the mall for example because i know people are dicks and like to touch and sit on bikes. god help anyone i ever catch sitting on my bike thats all i gotta say. when you keep it at home keep it in the garage, mines locked up in the garage and ive got it tied up through the frame with an anchor running into my floor. so they either have to cut through a solid piece of steel cable or rip out the anchor, good luck to both. plus my garage and work shop are both alarmed. in the end if someone wants it theyre gonna take it, but the idea is just to make it as hard as posslble for them. i do hope one day to catch a thief trying to steel something i have so that i can kick their skull in.