I posted this elsewhere, so I thought I would copy and paste, it's kinda long though. But hey, for a Kryptonite mini-U try a: 1)Bic Pen (You'll need something ot tap on it with, the lock itself or a hammer will do to tap it into position. The plastic is pressed around the tumblers and mimics the shape of the key. It's kinda hard at first.) 2) A grinder with diamond wheel. Get at least five new wheels. If you can't use a pneumatic grinder, and have to use electric, it will take a while. Don't use a torch, it will just make a mess. 3)Jaws of life, the old hydraulic ones are way better, but the newer battery operated ones are good too. 4)Three foot bolt cutters with "Hastelloy X" jaws. It will ruin the cutters. Carbide anything will chip. 5) A 50-100 ton brake press with A or E class cutting jaw add-ons. That means the lock goes to the shop. So, if it's locked to something, you cant do number five. 6) I have never tried the liquid nitrogen approach. Very dangerous. Don't spill it on your foot or breath in the fog.

I spent ten years as a CNC Machinist in the medical and aerospace industries before getting into Computer Science. There are a lot of guys out there that know a lot mor ethan I do, but I can steal any bike if I don't mind a crowd. I don't steal bikes, I jus tknow how. I have knowledge of unusually hard metals and their characteristics and I can also defeat any bicycle lock. I can pick most combination locks by feel in under a minute. I must say I see alot of people using the U lock through the back wheel, "back wheel to steel" method, and it is very disappointing. I have stolen bikes (testing) with the NYFU lock going through the back wheel by simply cutting through the tire, rim and all in about five-eight seconds. REAL quick. Give the bike a big heavy yank (being 6'-4" helps), and thus yanking the U lock through the cut in the rim, and you've got yourself a new, used bike with a crappy back wheel. It's also on YouTube too. I have used about everything to cut through these different Kryptonite locks. Pad locks with covered shackles are good, except against the two pound mallet attack or the grinder. The grinder will go right through teh whole body of the lock, but the shackle is quicker because a very small section is still exposed. The lock combination that I am unable to defeat <in a reasonable amount of time> is a Kryptonite New York Noose over the top of the upper, rear triangle and down through the wheel and frame locked to the bike rack, along with a NYFU (Fuhgettaboudit) through the top tube and around the bike rack with a cable through the front wheel to NYFU lock. My bike is Kona freeride bike so it has the through axle in the front which is an additional annoyance when stealing, but the more annoying a job is, the less anyone wants to do it. The NY Noose uses a mini U lock for the chain, which has several links and a big ring that the chain itself slides through creating a loop type application, but the shackle diameter is very thick and the "U" is so small the only thing anyone can get in there is a flat head screwdriver, providing you are using it on the Noose. The purpose of the mini U lock is that it can't be leveraged. It is so stout, that the strength-to-diameter ratio is excellent. The chain it is used with is even stronger, that makes the mini U the weakest link; which is still pretty damn strong. The three foot bolt cutters can go through it, but one handle has to be put on the ground, and then I sit and bounce (I wiegh 340) on the handle and after about a few minutes it goes through the mini U lock. It ruined the bolt cutters, dented them real bad. But they won't work on the Noose, the links are just way too hard and they have a hexagonal profile, and again, it ruined the bolt cutter jaws, it dented them so far in I couldn't use them anymore. It made big marks on the links, but no fracture. The grinder worked on all the locks, but it took about twenty minutes with an air compressed wheel grinder and several new diamond wheels. The acetylene torch melted the NYFU a little, but could not cut it, and the NY Noose was even tougher against a torch. The triple heat treated Boron Manganese steel was harder than I thought. A six foot A-2 pry bar and three big greasy guys can start to work the NYFU lock loose, but the frame got ruined on the test bike and was bent pretty bad, un-rideable. Yup, you can break through any lock if you have the tools, the time and the know how. I know that with the correct tools, and the correct know how, it would take a really good thief about twenty minutes to get my bike if he had a partner. I used to put the locks low, but working a pick on the ground is easier because you can lay all your tools right next to your head and make quick work of it. If the locks are up high, I can't ge the leverage I need from the three foot bolt cutters, but the disc picks and bic pens can still be used. So up high, I eliminate at least one break method. So, I chose these locks and these postitions to lock my bike up so that at least it has a fighting chance of being there when I get back. I carry them in a trunk bag mounted on a post mount rack. Since I am heavy, I cannot feel the weight of the locks when I ride except when climbing a 10%+ grade hill. Jaws of life worked pretty good, used two batteries and took three minutes. But they are real big, cost alot, and I think you have to be a firefighter or law wenforcement to purchase one. The new ones are battery operated so they are way slower but still useful and more portable that way. Use a copule locks and keep em up high, no combination locks. Try to get one flat-keyed lock and one round-keyed lock.That way if some smart ass actually knows how to do the bic trick on the disc lock, you still have aflat key to defeat. The more tools a thied needs to take your bike, the more likely that he will leave it alone. Always park your bike out in the open. Maybe when you get back to your bike, the only reason you will have a crowd around your bike is because you have a cool looking bike with a crazy locking method. Just be ready for all of the "I know a guy, who knows a guy, who knows a guy that can get all of those locks off in ten seconds. . ." There's always one. Your reply should be, "Well, if my bike comes up missing, now I know what you look like." Hope this helps and happy trails.