RECUMBENTS IN 4 FLAVORS
Recumbents are generally divided into long-wheelbase and short-wheelbase categories, depending on whether the front wheel is in front of the pedal assembly or behind it. Each type has its good points and disadvantages.
Short wheelbase recumbents have a smaller turning radius and greater maneuverability. They have a more equal weight distribution between the two wheels, making front wheel skids less likely. Shorter overall, they are easier to store and transport by car.
On the downside, the short wheelbase designs can have a problem with the drive chain. Unless the rider is seated very high off the ground (by recumbent standards) the chain cannot run straight between the chainwheels and the rear sprockets, because the front wheel will bump into it when it is turned to the side. Most short wheelbase machines have the chain run over an idler pulley or sprocket. Running the lower, un-tensioned run of the chain over such an idler is no problem, but they also usually need to run the upper, tensioned run of the chain over an idler as well. Such as idler has to be very strongly supported, and have excellent, load-carrying bearings. Even the best of them make a significant reduction of the efficiency of the drive chain.
An alternative is to run two chains connected by a jackshaft above the front wheel. Either approach increases the complexity of the drive train, adding friction and adding more moving parts to maintain.
Short wheelbase recumbents often use a 16" or 17" front wheel to improve the chain clearance. Such small diameter tires have a reduced lifespan, especially when they are loaded as heavily as they are in this application.
Long wheelbase recumbents are generally more stable than short wheelbase models, thus easier to learn to ride. They pitch less on rough surfaces. Theoretically, they can stop faster than any other type of solo bike, because the front brake can be applied very hard without any danger of "pitchover". Their chains are longer than those of upright bikes, but no more complicated, with a very straight chainline. The long run of chain even allows the use of cross-chain gears that would cause problems on a conventional upright bike.
Long wheelbase recumbents usually use 20" front wheels, which are lightly loaded, so the tires last quite a long time. Replacement tires in this size are available everywhere. Some long wheelbase models are compatible with low-rider front racks, making them good for loaded touring.
Long wheelbase recumbents are less maneuverable than short wheelbase ones, more cumbersome when they are not actually being ridden.
High Bars vs. Low Bars
The other great divide in recumbent design is handlebar location. They can either be above the riderís lap, or underneath the seat.
High bars are mechanically simpler, being attached to the steerer tube by a conventional handlebar stem, and having no additional moving parts. High bar recumbents are easier to learn to ride. The high bars also provide a good place to mount a fairing, bottle cages, cyclocomputers, maps, horns, bells, etc.
High bars slightly complicate mounting and dismounting, and they must be turned very far to the side to steer a long wheelbase machine through a tight corner.
Low bars are more complicated mechanically, because they are not direct-drive. The handlebars are mounted under the seat on their own pivot, and there is a tie rod running forward to the fork crown. They take a bit of getting used to, but many riders find the position more relaxing once accustomed to it. Low bar bikes may have optional attachment points for the tie rod that allows steering "quickness" to be varied.
Beginners start out with 1:1 steering, but a more experienced rider can increase the maneuverability of a long wheelbase bike by setting the tie rod so that the fork turns faster than the handlebars.
Low bar recumbents can be quite terrifying to first-time riders. The tie-rod linkage is an additional mechanical complication, and requires periodic maintenance and adjustment. Generally low bar recumbents cannot be ridden "no hands".
All four of these designs have real virtues and drawbacks. Each variation is probably ideal for some riders, and all share the general virtues and drawbacks of recumbents.
Recumbents and Safety
One objection to recumbents that is frequently voiced is the perception that they are more dangerous than conventional bikes. I do not believe that this is based in reality. Recumbents differ in two fundamental ways from uprights: visibility and crash-worthiness.
Visibility is a two-way matter: how well can the bicyclist see... how well can he be seen.
There is no getting around the fact that a recumbent rider cannot see over the roof of cars as well as an upright rider, especially a tall one. On the other hand, a recumbent rider still probably has a clearer field of view than an automobile driver.
Theoretically, a recumbent, being lower to the ground is less visible to other road users than an upright bicycle. To a considerable extent, however, this is offset by the uniqueness of recumbents. Drivers see conventional upright bikes all the time, and often ignore them because they are so commonplace. Recumbents, however, attract attention. If you are really worried about this, you can use a flag.
Most bicycle accidents do not involve other vehicles. (If you are going to crash on a bike, a recumbent is the best way to go.) If you crash head-on into another vehicle or a stationary object,
the feet-first position of the recumbent rider is the best possible one. If you fall over sideways, you do so from a much lower height.
Add recumbents greater stopping power and you have to judge them substantially safer than upright bikes.
(This article originally appeared in the May 1992 issue of American Bicyclist & Motorcyclist. For more writing by Sheldon Brown, visit his website at www.sheldonbrown.com.