In my storied career, I've had stolen 1 saddle, 1 rear wheel, 2 setes of lights, 1 bike-specific coffee mug (including an old latte), and 1 complete bicycle. Even writing this list makes me feel a little violated. But I write it to emphasize the reality of theft for the uninitiated.
Because of the above occurences, I've gained a healthy respect for the lowness of humans, and a bit of practical knowledge on locking stuff up. The basic gist: attach your frame to some immovable object, then attach securely to the frame the removeable bicycle stuff (at least the stuff that a.) you're attached to, and b.) could be of interest to some cad). If this were the entirety of the formula, there would be no need to write on the subject. However, there is a controlling variable: you generally have to carry your locking mechanism with you while you travel around. So, you can't just use a length of chain from the anchor line of an ocean-going vessel.
The optimum balance I've found:
.... In combination with:
This Kryptonite U-lock (the "Evolution Mini") falls under the category of Very Good Things. (Other examples: that perfectly fitting pair of jeans, that deep-gloss black paint on a 70's motorcycle tank, my perfectly aged 1970 Brooks B15 Special Narrow... you get the idea.) This u-lock is strong, small, relatively light—and opens and closes with a smooth, precise, satisfying action. I use it in tandem with the 4' plastic-enclosed steel cable. Kryptonite sells a 7' cable as well, but I just can't bring myself to buy one that long. If they made a 5' cable, I'd snap it up. Then I could secure both my wheels and my saddle. As it is, I have to choose between my rear wheel and my Brooks, and the Brooks obviously wins. Though I don't have a quick release rear wheel, I'm setting myself up to be a victim of my own Point 3, corollary i. below.
At any rate, the below diagrams illustrate how I attach everything. If you have agressive geometry, narrow (steel) tubing, and a relatively small-diameter post to attach to, you can enclose the front wheel, the frame, and the post within the u-lock. You could then protect both your saddle and your rear wheel with the four-footer.
Forgive the drawings; I had my assistant Lucas do them. He chose to use Microsoft Paint and a mouse. Poor fool; I pay him minimum wage, and he doesn't realize that with work like this, he'll never go anywhere.
Fig. 1.1
Fig 1.2
Before I leave the topic, a few parting shots:
1. If you travel to the same place(s) every day, it might be worth your proverbial while to leave a large u-lock in each of the locations. Then you'll never have to carry the five-pound beasts with you.
2. Some people will take off the various components on their bike-- wheels, saddle, etc.-- and lock them all into the u-lock. This is fine, and certainly secure. I've done it. But it's certainly more work than is saved by not carrying a good cable.
3. A primer in the Philosophy of Theft
a) If you like it even a little, there is somebody that would be willing to steal it.
b) You cannot apply statistical analysis to the prevention of theft: if there is "only a one-in-a-hundred chance that someone who would steal this bike would be walking by today", then your bike will be stolen. If it is physically possible to steal your bike, its theft is ineluctable. (Of course, this within parameters. It's always possible, on some level.)
Corollary i) The only factors you can use to determine if your bike is secure are physical. Exempli gratia: My bike was stolen between the hours of 11:00am and 1:00pm, in the middle of the busiest part of a busy campus, having been locked to a secure base with a thick cable lock. Principle: I left open the physical possibility of its being stolen by not using a good u-lock, and I relied upon human factors. "Well, nobody would try to steal it here, in the middle of the day..."
It was once reported of a certain prudent: "He needed no one to bear witness about man, for he himself knew what was in man." You are wise to apply the same to your two-wheeled Beloved.
