Security - U-locks

Some U-locks (sometimes called D locks) are very thick and strong. They probably are the toughest kind of lock.


Closed U-lock for bicycle Opened U-lock for bicycle

Thieves could try to fit powerful prying tools within that U-shaped space. There are a couple ways to stop that:

A bike U-lock might weigh 1.5 kg (3.3 pounds), and a motorcycle version could weigh twice as much. There's a lot of variation in weight between different models. Those figures only serve to give you a general idea of what you will be carrying the next time you bike up a hill.

The following are some impressive U-locks I found:

In the USA, Kryptonite and OnGuard seem to be the most common brands found in bicycle retail outlets. If you want an ABUS U-lock, you could pick a model from the ABUS website, and then ask a reseller like lockitt.com or a local motorcycle accessory store to order it.

The better U-locks are usually expensive, often more than US$70 and well over US$100 for an ABUS model. They might be worth it to you, even if the lock is worth more money than the bicycle it guards. Losing a bike could force you to disrupt your schedule, take an expensive taxi ride home, spend time reporting the theft, and maybe spend time and money shopping for another bike. If your bikes are stolen repeatedly, then the lock makes even more sense.

However, the locks I demonstrate here were fairly cheap. I bought older versions of OnGuard's Brute Mini U-Lock and the longer Pitbull Mini LS U-Lock. They offered a combination of narrowness and thickness which was lacking in the U-locks I found in retail stores.

Kryptonite offers a product similar to my longer lock but with a thicker U, and ABUS has a family of locks, from short to long. If you order more than one of those ABUS locks (like a short and long one), you can have them all keyed alike; I don't know if that's possible for the other brands.




You probably want to avoid using a U-lock that has a tubular-shaped key. See my page about bad locks.




One online source I read claims that there's a vulnerability with the kind of U-locks I'm showing in the photos here.

Notice that the key is inserted into that orange crossbar's end which sticks out past the U. A thief could get a strong steel pipe whose inner diameter matched that part of the orange crossbar which is sticking out. If the thief slipped one end of the pipe onto that protruding part of the U-lock, then supposedly it's possible to bend the protrusion and somehow open the lock.

I think this is why newer U-locks have the key inserted into the center of the crossbar instead of the end.

However, I'm not sure whether this trick works against locks as thick and strong as the ones pictured on this page. Hopefully, most thieves would not go get a pipe of the right size, anyway.




Here's an example of how you could use a U-lock. If you want to lock the rear wheel to the frame, you could slide the U through the bike as shown.


Parts of bicycle to be locked, within the U of the lock

Then walk to the other side of the bike and slip on the locking bar. Turn the key and pull it out.


Parts of bicycle are locked, within the U of the lock



Shown below are other ways to lock a wheel.


Frame and front wheel of bicycle locked together with U-lock Frame and rear wheel of bicycle locked together with U-lock

However, if you are going to bother carrying that heavy lock, you might prefer to have it lock up your entire bike. To do that, you must remove the front wheel and place it next to the rear wheel. In the photo below, I have trapped both wheels, the bike frame, and a metal post, all inside the lock.


Frame and both wheels of bicycle locked to a pole using a U-lock

Unfortunately, when I tried that with a larger bike, I discovered that my U-locks were too small to enclose everything. Before buying a lock, think about how you want to lock your bike. Use a ruler to measure the size you will need.

Following are some more examples of locking with a U-lock. In both of the top photos, the front wheel has been removed and placed by the rear wheel.


Both wheels of bicycle locked to a pole using a U-lock Seat stays and both wheels of bicycle locked to a pole using a U-lock

Front bicycle wheel locked to a bike rack stand using a U-lock Frame of bicycle locked to a pole using a U-lock

A reader of this website made an interesting point about that bottom-left photo. A thief could easily steal that bike in one of two ways. The first way would be to simply detach that wheel from the bike. The thief could buy a replacement wheel. A second lock connecting that wheel to the frame would solve the problem, but that might be too much trouble.

The other way to steal it would be to let the air out of the tire, press the wheel against the grey metal tube, and flip up the left part of the lock. Depending on the sizes and positions of the various items in that photo, it might be possible to then slip the lock away from the tube; the thief could take the bike and deal with the lock later. So you should NOT use a U-lock this way unless you're sure the lock is somehow trapped in its place.