Looking beyond the familiar classification of road bike, hybrid, mountain bike to some of the more esoteric varieties of bike available.
The vast majority of adult bikes sold in the developed world today fit on to the road-hybrid-mountain bike spectrum, but there are all manner of other types of bike, some weird, all wonderful.
The following is just a brief list but will in due course include links to more detailed discussion of the various types.
Tandem. Two wheels, two riders. There are road tandems, hybrid tandems, mountain bike tandems and track tandems (the tandem sprint on the track is an awesome, if not terrifying, thing to watch!). With two power sources but little more air resistance than a solo bike, tandems can be very fast indeed.
Triplet. Two wheels, three riders. Very rare, normally a one-off build. Quads, quints, etc, also exist.
Tricycle (or trike). Three wheels, one rider. Normally, but not always, have single wheel at front and two (one driving) at rear. There are utility trikes, useful for people with impaired balance or mobility, and there are road trikes - especially popular in Britain, for some reason, where they are regularly seen in road time trials. I have never heard of a track or mountain trike - now I wonder why that could be?
Tandem trike. Three wheels, two riders. A rarity - again less so in Britain than most other places. Officially recognised for time trial and road distance records.
Touring bike. Self-explanatory to a degree, but can vary widely. Light tourer might be a road bike with a little extra room for mudguards and carrier; expedition tourer would owe much more of its ancestry to mountain bikes.
Track bike. Ultra light and stiff, with single fixed gear. Not to be missed if you have the chance: read a blog entry on this.
Recumbent. Defined by fundamentally different riding position to conventional bike; rider may be sitting or even semi-reclining. May have two wheels or three. Lower profile makes them, at least theoretically, faster; the fastest bikes of all are streamlined recumbents. Also favoured by some long-distance tourists, citing greater comfort as well as easier pedaling.
Hand-bike. A recumbent with cranks operated by hand, for riders who cannot use their legs. Have been ridden over long distances and at impressive speeds.
Cyclo-cross. Used for off-road riding long before the advent of the mountain bike. Basic design resembles road bike but with wider clearances (for mud!) and knobbly tyres. Lighter than mountain bikes, riders tend to carry their bikes over severe obstacles rather than riding them.
BMX. Small wheels, rigid frame, used mostly for stunts and jumps - often seen sharing skateboard parks (usually amicably!)
Folding Bike. Basically self-explanatory but widely variable, from utility ‘shopper’ bikes to fast road folders.
Cruiser. Also called, confusingly, ‘street bike’. Long wheelbase, slack frame angles, laid-back riding position. Slow and heavy, designed for lazy cruising (and some would say, posing). Often customised, with a Harley-Davidson aesthetic surfacing frequently.
Of course there are even more esoteric categories - unicycles, cycle rickshaws, and so on, but where do you stop?
