Customer Reviews
Best lock you can buy! 
2008-09-07
I live in a city where there is an unbelievable amount of bike theft. When I got my new bike, I knew I had to go to extra lengths to protect it. After doing a lot of research, this lock stood out as the most effective at preventing theft. It is nice to know I don't have to worry about my bike. Thieves just pass on by, looking for easier pickings.
Good lock. inexpensive. 2008-08-12
This lock is very strong. IMHO, no one is going to steal your bike with this thing on it unless you have a $2000 bike that they really want. It's also relatively inexpensive and light for the job it performs.
Lock okay, mount less so 
2008-05-26
The lock itself seems sturdy enough. At least one review found it resistant to most attacks. ([...]) It is long enough to capture both the front wheel and the frame, along with a fencepost, which is a good thing if you have a quick-release front wheel (which can be removed in 2 seconds without tools.)
However, the lock is too big to mount inside the frame of my 53 cm road bike. (The mount requires a little clearance above the lock to allow the lock to be slid up out of its mount.) That is not a small bike, and there are many bikes with smaller frames.
Luckily, the lock and mounting system is flexible, accommodating nearly any tube size. The piece that takes the lock can be removed by unscrewing four screws, and rotated 90 degrees. Also, the mounting piece on the lock itself can be rotated by loosening a set screw. Those two things mean the lock can be mounted several different places on the frame. The instructions give several suggestions, with a list of pros and cons of each. One problem with a few locations is that the lock can interfere with your pedal stroke.
The mount itself is not all that easy to attach to the bike. You have to place an thin, H-shaped piece of rubber (included) between the mount and the frame to keep it from sliding around. The rubber isn't attached or glued to the mount for some reason (possibly because it is a last-minute addition) so it is easy to lose. It also doesn't fit the mount exactly. I dropped it few times before I got the mount on securely.
These new mounts use a strap of nylon that you wrap around a frame tube and pull tight, then tighten further by turning a ratcheted bolt that takes up the slack. (That operation requires a metric hex wrench, which you are likely to have because lots of other things on the bike require metric hex wrenches.) You can get pretty good tension on that strap. However, depending on where you put the mount, something (like the rear reflector) can block access to the tightening bolt.
Unluckily, I chose a location that did interfere with my pedaling (it is impossible to be sure whether or not a position will interfere with pedaling without actually mounting it in that position.)
And this is the major flaw with the mount. You cannot reposition it without cutting the strap or probably damaging the mount. The ratchet, being a ratchet, turns only one way. So you can only tighten the strap, you can't loosen it. You can try to turn the ratchet the wrong way, but that usually breaks the ratchet, and this one doesn't seem all that robust. So I am waiting for tech support from OnGuard for advice. If need be, I will just cut the strap and get a new mount from REI (unlike Amazon, REI offers a lifetime guarantee on everything it sells.)
Locking Mechanism Broke 
2008-03-09
While the lock itself does what it is meant to do (keep my bike from being stolen), the locking mechanism has broken. I dropped the lock once and 1) the plastic casing around the locking mechanism cracked, 2) there is a visible gab between the metal locking section in the center of the lock (the part that is metal and not covered with plastic) and the body it is connected to, and 3) I really have to finagle the key to make it lock/unlock. Not exactly the best construction...
Ammendment to previous negative review 2007-11-22
OnGuard PitBull STD 5003 Bicycle U-Lock
Strong lock but the mounting system sucks. Will not tighten enough to keep lock in place. Very little thought went into this mounting bracket and it shows. Had a problem with the mounting section on the shank sliding down rendering the lock useless. Contacted the company and they told me to buy a wrench at my local hardware store to fix it. I do not consider that customer support
Amendment to above review. It would seem this lock came with a ratchet mounting system when it first came out which is what I got. I emailed the company and sure enough, they have a new mounting system which is WAY BETTER. They sent it gratus which I think is very commendable. I recommend this lock wholehartedly if you get the new mounting system.
bike lock 2007-11-01
Utilizing OnGuard's new ultra steel shackle, M-Cylinder technology and Dual Steel Bar lock mechanism that delivers up to 10 tons of pull strength. On top of all these great featurs OnGuard also includes 4 laser cut keys and 1 light key for night time use. 13mm hardened ultra steel shackle. Double bolt locking mechanism. Vinyl coated and weatherproof.
Very solid, dependable lock 2007-06-27
This lock is a great value. It feels very well-built. You get 5 keys, including one "master" key with a LED light, which is really neat. The silver part in the middle rotates to protect the keyhole from dust/damage, and maybe foil potential thieves. The "U" part is long enough to secure my rear wheel and frame to any poles.
The mounting bracket/lock rattles quite a bit when riding...
lock 2007-05-13
great price.strong lock.The light on the key stopped working shortly after using it.
Excellent 2007-01-10
A product that is well worth the money, OnGuard makes the best bike locks that I have seen. Fast and easy to use, this lock is a nightmare would be thieves prefer not to think about it. I highly recommend this product to anyone who needs a good bike lock.
