Reddit reviews ABUS Mini Round Shackle U Lock, 5.5"/15mm

Totally depends on the bike, I leave my beater locked up outside year-round in south kensington.

If your bike looks like anything more valuable than scrap metal, you can count on people trying to steal it. Even if it looks like scrap metal, scrappers might try to steal it.

That being said, the convenience of not having to carry my bike in and out makes it worth it.

Definitely a get a sturdy hardened-steel U-lock through the frame (I use this one), and something to lock the wheels. Cables are pretty easily cut, so U-locks are more reliable. But I've been using locking skewers for like seven years now. I've been using these for maybe four years, and haven't had anything stolen. Before that, I used a different kind and had three wheels stolen over that period (which if you consider you can get a replacement wheel/tire for $50, isn't that bad).

I think the critical thing is knowing that eventually someone's going to fuck with your bike (even if they don't steal it, I've had people spraypaint it and slash the seat), and that it's just a matter of time. Since it's relatively trivial to get a perfectly good replacement beater for <$150 on craigslist, you just gotta roll with it.

I personally have used this Abus mini u-lock for more than a year, and am happy with it. I know Kryptonite is stronger, but this lock is just so much lighter, I could easily carry it in the back pocket of my pants.
When locking up at night i also use this Kryptonite cable to secure the wheels.
If you want a lock stronger, more expensive, and heavier check out the Kryptonite New York addition lock as far as I know it’s the toughest one out there, but I’m fine with the Abus