I'd use a large chain and the beefiest lock you can manage. The sort of thing you'd use to lock up a motorcycle.

37/80 + 14KS. It's a tight fit, heavy, and expensive but they work.

Same suggestion but also multiple locks - I always use 3 (D, chain, metal bar) in London and I've never had a problem, even with occasional overnight leavings. If the bike next to yours only has one, you're already ahead in the risk calculation.

I use the lock recommended by the Lockpicking Lawyer [1]. You can buy them at Tip Top Bike Shop in Temescal (no affiliation but support your local bike shop!).

The guys at that bike shop said that for example if I want to ride to Lake Merritt and walk around for a while, I could lock it near the boat house and leave it for a couple hours as long as it’s daytime. They said don’t leave it overnight which I would never do. If I’m going to the grocery store, there’s so many people coming in and out, it’s just not the kind of environment where a bike thief is super likely to come in with an angle grinder and start attacking my chain lock. It’s interesting because we imagine this place to be high theft and I guess on some level it is, but having a lot of people around does feel like a decent deterrent, along with a good lock. I’m more worried about my panniers, which aren’t locked to my bike and lift right off with no tools. I wouldn’t use those if I was leaving my bike for a while, but again at the grocery store people are coming and going so often it would be pretty risky for a thief to come and mess with bikes.

Or if I'm going to a coffee shop, I'm always within 20 feet of it and I can see it, and it’s locked. That’s fine. If I’m riding to a friends house, I leave the bike inside their house when we go do stuff. At the bike shop, I just bring the bike inside the shop with me.

It wouldn’t be a bad idea to start with a cheap bike, and use the cheaper BBS02 motor and a cheaper battery. Then if it gets stolen, as much as that sucks, it’s easier to recover. Though cheap batteries present a fire risk. A lot of people on Reddit stand by the the UPP batteries, but Louis Rossmann had his catch fire so opted for the EM3EV battery at twice the price. I also got a big battery which isn’t strictly necessary, though it’s nice.

[1] https://youtu.be/SpVOTEOMRuE

A friend of mine got his $5k bike stolen in the middle of downtown Mountain View in plain sight.

If you don't use something like an ABUS 37/80 + 14KS, your shit is going to get jacked in Oakland because of zillions of thieves with portable angle grinders in backpacks and teams riding around in vans looking for easy marks.

Don't leave anything valuable outside in Oakland unless you want it to disappear because people on drugs are always looking for property to convert into their next fix.

Thanks it’s good to know.

Get bike insurance, for this exact reason! Your renter's insurance might also cover bike theft.

I recommend using multiple locks. What is important is their usability: try to make sure that the lock can be attached to the frame and that it doesn‘t rattle, also needs to leave enough space for lock up your bike to things that are not the typical bike rack, like lamp posts. I still recommend U-Locks but they‘re so bulky and can seldomly be attached securely to the frame without rattling, so I ended up putting it into my panniers all the time. If you know that you will always commute to a bike rack that allows you to use one of the smaller, hand-sized U-locks, go for it. A folding lock is less secure but very flexible for locking up and often comes with a great, hassle-free frame mount. A cafe lock is not so secure either but is super quick to lock up. Having a complicated lock routine for a bike you can’t afford to have stolen makes you hesitant to stop for short errands or exploration trips by foot. So try to look out for quick, fun to use ways to add security barriers for thieves, because you essentially want to make it slow to break through those barriers and that it requires multiple different tools. Also, you can hide an AirTag or dedicated trackers in non-obvious places.

My wife's ebike has two ABUS locks D locks that share the same key, very convenient.

My primary form of transport is an e-bike, and I'm happy to lock it up in public, because I kind of overdo it: I have a >6kg chain lock [1] and >2kg D lock, there's a built-in frame lock through the back wheel (nothing major, just another obstacle), and the bike won't start without its key. I lock to a bike stand with two locks if possible.

[1] https://www.kryptonitelock.com/en/products/product-informati..., note the big final ring that the whole chain fits through to get more reach.