A recumbent bicycle is a bicycle that places the rider in a laid-back reclining position. Most recumbent riders choose this type of design for ergonomic reasons; the rider’s weight is distributed comfortably over several square feet of the back and buttocks. On a traditional upright bicycle, the body weight rests on a few square inches of the sit bones, the feet, and the hands.
Most recumbent models also have an aerodynamic advantage; the reclined, legs-forward position of the rider’s body presents a smaller frontal profile. A recumbent holds the world speed record for a bicycle, and they were banned from international racing in 1934.
Recumbents are available in a wide range of configurations, including: long to short wheelbase; large, small, or a mix of wheel sizes; overseat, underseat, or no-hands steering; and rear wheel or front wheel drive. A variant with three wheels is a recumbent tricycle .
Description
Recumbents can be categorized by their wheelbase, wheel sizes, steering system, faired or unfaired, and front-wheel or rear-wheel drive.
Wheelbase
Long wheelbase (LWB) models have the pedals located between the front and rear wheels; short wheelbase (SWB) models have the pedals in front of the front wheel; compact long wheelbase (CLWB) models have the pedals either very close to the front wheel or above it. Within these categories are variations, intermediate types, and even convertible designs (LWB to CLWB) - there is no "standard" recumbent.
Wheel sizes
The rear wheel of a recumbent is usually behind the rider and may be any size, from around 16 inches (410 mm) to the 700c of an upright racing cycle. The front wheel is commonly smaller than the rear, although a number of recumbents feature dual 26-inch (ISO 559), ISO 571 (650c), or ISO 622 (700c) wheels. Notable among these are "highracers", such as the Bacchetta Corsa and Strada or Volae Team, or the "LWB-style" RANS Stratus XP. Larger wheels generally have lower rolling resistance but a higher profile leading to higher air resistance. Highracer aficionados also claim that they are more stable, and although bicycle stability increases with the height of the center of gravity above the ground, the wide variety of recumbent designs makes such generalizations unreliable. Another advantage of both wheels being the same size is that the bike requires only one size of inner tube.
The most common arrangement is probably an ISO 559 rear wheel and an ISO 406 (20-inch) front wheel. The small front wheel and large rear wheel combination is used to keep the pedals and front wheel clear of each other, avoiding the problem called "heel strike" (where the rider's heels catch the wheel in tight turns). A pivoting-boom front-wheel drive (PBFWD) configuration also overcomes heel strike since the pedals and front wheel turn together. PBFWD bikes may have dual 26-inch (660 mm) wheels or larger.
Steering
Steering for recumbent bikes can be generally categorized as
- over-seat (OSS) or above seat steering (ASS);
- under-seat (USS); or
- center steering or pivot steering.
OSS/ASS is generally direct—the steerer acts on the front fork like a standard bicycle handlebar—but the bars themselves may extend well behind the front wheel (more like a tiller); alternatively the bars might have long rearward extensions (sometimes known as Superman or Kingcycle bars). Chopper-style bars are sometimes seen on LWB bikes. USS is usually indirect—the bars link to the headset through a system of rods and bell cranks. Most tadpole trikes are USS. Center steered or pivot steered recumbents, such as Flevobikes and Pythons, may have no handlebars at all.
Drive
As with upright bicycles, most recumbents are rear wheel drive. However, due to the proximity of the crank to the front wheel, front wheel drive (FWD) can be an option, and it allows for a much shorter chain. One style requires the chain to twist slightly to allow for steering. Another style, Pivoting-boom FWD (PBFWD), has the crankset connected to and moving with the front fork. In addition to the much shorter chain, the advantages to PBFWD are use of a larger front wheel for lower rolling resistance without heel strike (you can pedal while turning) and use of the upper body when sprinting or climbing. The main disadvantage to all FWD designs is "wheelspin" when climbing steep hills covered with loose gravel, wet grass, etc. This mainly affects off-road riders, and can be ameliorated by shifting the weight forward, applying steady pressure to the pedals, and using tires with more aggressive tread. Another disadvantage of PBFWD for some riders is a slightly longer "learning curve" due to adaptation to the pedal-steer effect (forces applied to the pedal can actually steer the bike). Beginner riders tend to swerve along a serpentine path until they adapt a balanced pedal motion. After adaptation, a PBFWD recumbent can be ridden in as straight a line as any other bike, and can even be steered accurately with the feet only.
Fully suspended bikes
Modern recumbent bikes are increasingly being fitted with front and rear suspension systems for increased comfort and traction on rough surfaces. Coil, elastomer, and air-sprung suspension systems have all been utilized on recumbent bikes, using oil or air-damping in forks and rear shock absorbers. The maturation of fully-suspended conventional mountain bikes has aided the development of these designs, which often utilize many of the same parts, suitably modified for recumbent use.
Fairings
Main article: Bicycle fairingSome riders fit their bikes with aerodynamic devices called fairings. These have two main benefits: they reduce wind-drag (typically increasing average speeds by around 2mph), and they keep the rider warmer and drier in cold and wet weather. Fairings are also available for upright bikes, but are much less common.
Seats
The seats themselves are either of mesh stretched tightly over a frame (as in the Gold Rush pictured) or foam cushions over hard shells like the Stinger pictured, which might be moulded (as here) or assembled from sheet materials. Hard-shell seats predominate in Europe, mesh seats in the USA.
Variations
Mountain bike recumbents
With the right equipment and design, recumbent bikes can be used for riding unpaved roads and offroad, just as with conventional mountain bikes. Because of their longer wheelbase and the manner in which the rider is confined to the seat, recumbents are not as easy to use on tight, curving unpaved singletrack. Large-diameter wheels, mountain gearing and off-road specific design have been used since 1999 on the Lightfoot Ranger. Crank-forward designs that facilitate climbing out of the saddle, such as the RANS Dynamik, also can be used off-road.
Lowracers
Lowracers are a type of recumbent more common in Europe among racing enthusiasts. These typically have two 20" wheels or a 26" wheel at the rear and 20" wheel at the front. The seat is positioned between the wheels rather than above them. The extreme reclined position, and the fact that the rider is sitting in line with the wheels rather than atop them, makes this type the most aerodynamic of unfaired recumbents.
Highracers
Highracers are distinguished by using two large wheels (usually two ISO 559 or 26"). This necessitates a higher bottom bracket than on a lowracer so that the rider's legs are above the front wheel, and this in turn requires a higher seat. The seating position may be otherwise identical to that on a lowracer allowing similar aerodynamics. "Racer" in the name implies that this will often be the case, since these bikes strive for speed.
Highracers are generally more manoeuverable than lowracers since their higher center of gravity allows stability at lower speeds (see Bicycle and motorcycle dynamics). Given the same seating position they may be faster than lowracers, since it is widely believed that larger tires have lower rolling resistance, although good data on this subject are scarce.
Hip and elbow injuries are more common on highracers than on lowracers due to the greater height from which the rider can fall. However, the injuries are very rare and seldom serious.
Semi-recumbent and
Recumbent Seat Covers
Recumbent Bike Seat Covers Spandex and Ripstop are the two materials we use. Each cover is custom made and fitted to the form we use.
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