One of the first items that bike enthusiasts examine-and those purchasing bicycles for police duty use should do likewise-is the frame. Nowadays, frame materials are usually some form of steel (chrome-moly is generally best), aluminum, carbon fiber, or titanium. Of these, aluminum seems to offer the best combination of lightness, durability, and cost for law enforcement duty.
Frame size gets into personnel-specific requirements. A single frame can fit only so many different sized riders. While you can fine-tune a bike with different height seat posts and handlebar stems, it's unrealistic to expect one frame to fit riders from, say, 5-foot-2 to 6-foot-5-and as we know, there can be a wide variance in officer sizes. For example, according to Chapman, the three-man bike unit at the Monterey PD ranges from 5-foot-5, 150 pounds to 6-foot-1, 200 pounds. That's why there are different sizes of frames.
Ideally, you want to get the proper frame size to match the intended rider, a task that the local specialty bike shop can help with. Mismatching frame size to rider can result in overuse injuries (especially knees) that can remove an officer from the street. But if the budget won't allow buying different bikes for the gamut of officer sizes, remember that you can better fit smaller frames to larger riders than vice versa.
Bike geeks also pay close attention to the components, especially the drivetrain (shifting system and front and rear derailleurs). Shimano components are probably the most widely used. Three sprockets in front (the crankset) are universally found; in back will be a six-, seven-, eight-, or nine-sprocket cassette, thus providing a total of 18, 21, 24, or 27 different gear ratio combinations or speeds to choose from. Thumb shifters are the most common and work well, although a few people prefer twist-grip shifting.
When it comes to pedaling, there's no question that keeping your feet fixed to the pedals is the way to go for the most efficiency. While there are those who prefer the old school "cages" that permit easy entry/exit, the clipless systems devised by companies like Shimano (with its SPD pedals and matching shoes) are more efficient and nearly as fast to get into and out of. All it takes is a little practice (usually a simple twist of the foot) to lock in or get out.
And with the right shoe made for the system, you don't sacrifice the ability to engage in a foot pursuit. The locking system in the shoe's forefoot can be somewhat recessed into the sole (which remains on the stiff side) so you're not running around strictly on the locking system which, of course, would offer precious little traction.
While center-pull brakes are simple, light, and work effectively, some bicycles now offer disc brakes at one or both ends. This is a fairly recent development in bicycles, though disc brakes have proven themselves in motorized vehicles and are the standard. Miniaturizing the system for bicycle use so it works well without a huge weight (and cost) penalty has been the goal, although companies like Magura and Shimano offer disc brake systems suitable for mountain bike use.
Suspension is now an integral part of the mountain bike scene as well. So much so that you almost can't find one today without at least a suspension fork. All police bicycles come with front suspension, and some models offer rear suspension as well. The jury is still out on which is better.
Some riders like the added comfort of front and rear suspension (also called full suspension), pointing to reduced fatigue and greater control in extremely rough conditions (as when descending a flight of stairs). Others feel that many rear-suspension designs allow too much up-and-down motion or "bobbing" while pedaling hard, as when climbing hills or trying to accelerate quickly.
Some companies equip their full-suspension bikes with "lockouts" that, in effect, turn the rear suspension as rigid as a "hardtail" simply by pushing a lever. Others have taken pedaling forces into account and designed proprietary rear-suspension geometry to negate bobbing and other energy-eating forces while allowing the suspension to work full-time.
The best way to decide which is best for you and your department's needs, of course, is to demo them in a variety of likely conditions-something that most bicycle vendors should permit.
Of course, if a full-suspension bike is ruled out, don't forget that you can equip the bike with a suspension-type seat post. They can run as little as $30. But, again, you get what you pay for. The Cadillac of suspension posts is probably the Cane Creek Thudbuster LT at around $150.