The obvious choice is the Kryptonite Evolution Mini, or a motorcyclist d-lock designed for disc brake, the Evo Mini is pretty small and combine that with an alarm padlock, it's perfect (that what I carried on my road bike).
mount them on the bike, a lots of people tend not to because it look ugly, but it's the best and easiest way to carry a lock, especially the Evo Mini, and you won't feel the weight while riding, it's static weight.
the small d-lock can be locked via the seatstay/wheel, but then again depend on the bike really.
The obvious choice is the Kryptonite Evolution Mini, or a motorcyclist d-lock designed for disc brake, the Evo Mini is pretty small and combine that with an alarm padlock, it's perfect (that what I carried on my road bike).
mount them on the bike, a lots of people tend not to because it look ugly, but it's the best and easiest way to carry a lock, especially the Evo Mini, and you won't feel the weight while riding, it's static weight.
the small d-lock can be locked via the seatstay/wheel, but then again depend on the bike really.