There is a lock on the market that can defeat an angle grinder, this lock is the absolute best lock bar none.
OnGuard RockSolid 8590, based on independent 2026 destructive testing. It literally turns grinder discs to dust and outperformed every other lock tested under timed angle‑grinder attacks! It cost $270, in America it's available only on E-Bay and at Walmart but not in any store, online only.
There is another one that comes super close to the OnGuard and that is the SkunkLock Carbon V2; it too turns grinder discs to dust. This lock is less expensive than the OnGuard at $184.
Neither of those two locks are lightweight, but you can't get a lightweight lock and expect it to stop anything, both are D locks, so if you need to lock up the bike either put your front wheel to the rear area of the bike so that the lock will go through both wheels and the frame or take the front wheel with you.
Those locks are for high crime areas, they're a bit of an overkill for low crime areas. Even though I live in a city of 250,000 people the bike theft type of crime is quite low, so all I use to use when I commuted to work was a 3 foot long Abus 6KS Security chain with a Master Lock resettable combination pad lock 1.2 x 2 x 3.87 inches model M175XDLF; both only cost me under $50, and never had any problems; that chain and lock will deter anyone who doesn't have an angle grinder. When I go touring/camping on a bike I take that same lock, but I use a vinyl covered security braided cable that is 1/2" thick and 5 feet long because it's a lot lighter than the chain, plus with the length I can lock it to a park bench or park table. Sure, a cable is fairly easy to cut, but this is only for when I'm sleeping, I never really leave that bike out of eye shot. Thick cable like mine are not slackers against cutting, any bolt cutter smaller than 24 inches won't cut it! You can nip away at with wire cutters; small hand tools will offer the theft a lot of pain and time to cut it; but they are easier to cut than most other bike locks except for cheap thin wire locks, or those super lightweight ZipLock looking locks.
You have to pick your lock based on the crime in the area in which you live and how paranoid you are.
The final option, if you have super nice bike, is to buy a standalone bicycle insurance policy, these will usually let you insure it for a stated value, so you can get enough coverage to pay for a brand new bike should it get stolen; or some homeowners policies will offer the option of a bicycle rider which usually means no deductible, but you have to get it appraised, so it will only be covered for that amount which when something is appraised it is done so at the used value thus you won't have enough money to get a brand new bike. And all insurance policies will require you to use a lock that they recommend, usually they'll recommend several different types. You will need a police report, or a file number, you should take pictures of the scene just in case.
LASTLY, BUT AN IMPORTANT READ: insurance that might come with a lock are a joke! There are a lot of loops you have to jump through to get a bike covered, these loops are so restrictive that most bikes will not be covered! Here is a list of those loopholes.
You must register the lock within 7 to 30 days of purchase, you must upload the proof of lock purchase, serial number and photos of the lock, failure to do any of that and it's too bad for you.
You must use the lock exactly as specified, meaning the lock must go through the frame to an immovable object, no quick release parts left unsecured; use the correct locking technique which varies by company. If the thief removes the pole or a sign or even a rack your claim is denied because the object was not secure! If you only lock the wheels or only the frame, you are denied.
Upon theft of bike, you must send in the original key, the broken lock, and the key number card, the original packaging the lock came in with bar codes intact, and the original receipt, lose any of that stuff and the claim is denied.
Must have a police report filed within 24 hours, which can be highly problematic because a lot of police agencies in large cities, at least in America, will NOT come out to take a report and hand it to you; of course, failure to do so claim is denied.
You must take photos of your locked bike every time you lock up your bike, those pics must show bike locked correctly, the object it is locked too, the location up close, medium range and longer range so they can see the if the area was exposed to the public and how well the lighting was, if not, claimed denied. Then if the bike is taken you have to take photos again of the broken lock or broken whatever it was attached to, and those pictures must show the site undisturbed, you can't move them around until after the pics are taken, failure do any of that and the claim is denied. If you parked it at night, you must take pictures at night, not during the day, if they deem the place you locked it up was not visible to foot traffic, claim denied.
Then you must prove the bikes value, you must have the bike purchase original receipt, OR a professional written appraisal, as well as any upgrades receipts. If the bike was bought used or can't prove its value your claim is denied.
They will deny coverage depending on which area you live, such as:
Canada
Some EU countries
Asia
South America
Coverage will be denied depending on how old the lock was at the time of theft. Most companies only cover the lock for 1–3 years from the date of purchase:
Kryptonite — 1, 2, or 3 years depending on lock tier
OnGuard — 1 year
ABUS — 1–3 years depending on model and region
Litelok — 3 years
If you are one day past those time frames, claim denied, this forces you to buy a new lock every X number of years, which in turn spins a profit for the lock company.
All those denial rules are not on the packaging generally; you have to go online to get the in-depth do's and don'ts from the company's website.
If you think you have followed ALL their rules and they still deny you claim, you will have to get a written letter from them stating why, then you might be able to take them to small claims court, but must bring in the printout of their rules and demonstrate to the judge you followed all the rules as written in their warranty statement and show all the proof you sent them. A lot of people have taken these lock companies to small claims courts. Some years back Kryptonite got into huge trouble in court, they had to change some of their restrictions and the way the restrictions read.
If by some super slim chance they accept the claim, then the payouts are as follows:
Kryptonite: $500–$5,000 depending on lock tier
OnGuard: $1,500–$2,000
ABUS: €500–€2,500
Litelok: £1,500–£3,000
And you must pay a deductible of $50 to $200 depending on the model, and of course that has to be paid before they pay you instead of them deducting the that amount from the claim check which is the way homeowners insurance or standalone bike insurance will do.
Most people will end up getting a free lock as a booby prize, big deal!
Don't buy one of the locks I mentioned and expect to get a claim paid out should the bike get stolen, buy the lock because of its high anti-theft rating.
