Fr mtn biker: go MTB...
Critics of the recumbent design counter the claimed advantages with a number of disadvantages:
* Balance. Balance is generally more difficult on a recumbent bicycle due to the lower center of gravity. It is easier to balance with a higher center of gravity because of the "pendulum effect" (it is easier to minutely change the angle at which upright bicycles lean). In addition, compared with riders of conventional bikes, two-wheeled recumbent riders have less scope for shifting their weight to steer or help balance the bicycle. As a consequence, riding at low speed and tight maneuvers can be more challenging on a recumbent. Of course, recumbent tricycles are a special case that are ideal for riders who cannot balance a two-wheeled bike.
* Starting and stopping. Because of the supine position, most recumbents do not allow the rider to push forward with the feet on the ground. This makes for slow starts and requires balance at low speed for a longer time. The recommended way to start an upright bicycle is by pushing off with one foot on the ground, and one foot on a high pedal. This is particularly advantageous if the upright bicycle is next to a curb or similar object. Recumbents cannot be started with this recommended upright bicycle technique. Starting a recumbent does not require great strength; it is a matter of balance and a skill which must be learned. It is best to learn from an experienced rider, who can help with a little push at first. Several rides may suffice to become confident enough of one's starting and stopping skills before becoming ready to ride in traffic or perform uphill starts. Recumbent tricycles do not require balancing and hence do not require any special skill in this regard. With many recumbent seats quite low it is often easier to get a foot down onto the ground on stopping than is the case from a conventional bike with the saddle set high for optimum pedaling.
* Maneuverability. Most recumbents have a larger turning radius and combined with the greater difficulties of balance, tight and low-speed maneuvers can be difficult. It is also very hard to jerk the front wheel onto curbs. Since the front wheel is often small, driving up unlowered curbs is very risky even with suspension.
* Uphills. A perceived and much debated disadvantage of the recumbent position is that it is more difficult to ride up hills. This is most noticeable during the initial period of riding a recumbent when the legs are not yet trained for the different muscle requirements. On a traditional bicycle, the rider can stand on the pedals and pull against the handlebars, although on a recumbent the rider can push against the seat. On either style, higher cadence reduces leg strain and fatigue when climbing. Recumbent tricycles are a special case, as riders can climb almost any gradient of hill (subject to tire traction) with appropriate gearing since balance (and hence speed) is not a consideration.
* A few designers have attempted to build bikes which convert from recumbent to upright for climbs. In practice the biggest difference is probably the additional weight of the recumbent layout combined with the difficulty of balancing a bike with a low center of gravity at speeds below about 5 mph (8 km/h).
* Length of the frame. Some recumbent bicycle designs use longer frames than conventional bicycles. This generally results in a weight penalty and in more flexing of the frame that causes a loss of power . The chain is two to three times as long as an upright and usually requires one or more idler pulleys. There is a small amount of friction in such pulleys which also reduces power slightly. Longer frame designs are more difficult to transport if the bikes are shipped, or put on racks on automobiles. Some manufacturers offer folding or break-apart designs, but these tend to be expensive. The longer distance from the handlebars to the wheels can be problematic for speedometers and cyclocomputers, including both wireless and hard-wired models. The distance from the handlebars to the crankset is likewise longer than a conventional bike and can give problems for cadence sensors.
* Constant position. While the riding position is comfortable and removes stress from the arms, it cannot easily be varied during a ride (as upright riders might stand for a hill), and some find that bottom brackets at or near hip level produces problems with cold or numb feet. Some riders suffer "recumbent butt," a pain in the gluteal muscles caused by their increased effort while being compressed. This can usually be addressed by adjusting the seat angle and pedal position. In a more reclined position, the weight is spread evenly between the back and buttocks. The rider of a conventional bike can stand up on the pedals to allow his legs to take up the shock of a severe bump in the road. The recumbent rider cannot (although many designs include suspension to alleviate this).
* Visibility of the road. The distance from the eyes to the front end is somewhat larger than an upright, and also the rider cannot lean forward. This leads to a bad insight angle at sharp corners. (Car drivers have the same problem, though less acute, since they are closer to the middle of the street.) In some designs - notably low-racers - the rider is also significantly lower than on a conventional bicycle and so visibility can often be obscured by fences, parked cars, etc. It is also a bit more difficult to glance back which can be addressed by adding helmet or handlebar mirrors.
* Visibility of the bicycle. In urban traffic, many recumbent bikes are below the eye level of many automobile drivers, although proponents suggest that the relative novelty of the design helps make drivers more conscious of them. Recumbent commuters often add flags, lighting, and reflective material to their bikes and gear to enhance visibility, and many refer to being able to see eye-to-eye with the automobile drivers as an advantage.
* Price. Recumbents are generally 10 - 15% more expensive than upright bikes of equivalent quality. Most are hand-built in comparatively small runs by independent manufacturers, usually with high specification components. At the low end, the vast majority of upright bikes sell for less than the cost of the cheapest new recumbent.
* Nonstandard design. Recumbents often have radically different shapes from diamond-frame bikes, so conventional bike racks, automobile carriers, accessories, and locks do not fit in the usual ways. Additionally the designs are difficult to mount in traditional bicycle work stands and often require a second person during derailleur adjustments to spin cranks that are too far from the shift controls and derailleur locations. Some bicycle mechanics may be reluctant to work on "nonstandard" bicycle designs.
* Safety. Although recumbent bicycles are generally considered safer than upright bicycles (as noted above), they do have some specific safety issues. A type of injury characteristic of recumbents called "leg suck" occurs when a foot touches the ground and the bike runs forward over the contact point, causing ligament damage and, in some cases, ankle fractures. The use of clipless pedals reduces this possibility by preventing the foot from slipping off the pedal. But with clipless pedals, remaining clipped in during a front tire or wheel failure at high speeds can result in the recumbent rolling over the rider and taking a clipped in leg or legs with it. This scenario, although very rare, can create severe spiral fractures of the femur rarely seen with upright bicycles.
* Overlap of heels with the front wheel during tight turns with some short wheelbase (SWB) and some compact long wheelbase (CLWB) design is known as "heel strike." This is only evident during tight turns and can be avoided by lifting the heel or pausing pedaling. It is similar in many respects to "toe strike" in upright designs, which is similarly dependent upon design, implementation, size of feet and their position on the pedal and the presence or otherwise of fenders/mudguards.