Introduction to recumbent bicycle basics.

Recumbent bicycles are often put into basic categories that describe the basics parameters of the frame design. Those categories include short wheel base under seat steering (SWB USS); short wheel base above seat steering (SWB ASS); long wheel base under seat steering (LWB USS); long wheel base above seat steering (LWB ASS). I build only short wheel base under seat steering recumbents. Some articles define short wheel base and long wheel base in terms of measured length, but with the advent of tandem recumbents in this field, and due to the differences in wheel base length based on body size it is more appropriate to use the definitions as relative terms: short wheel base design as compared to long wheel base design, for the same purpose (single, tandem, tall person)

This article enumerates my reasons for limiting myself to designing short wheel base recumbents. I also design short wheelbase under seat steering tandem recumbents.

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Advantages of the short wheel base recumbent design.

I am often asked "What is better a short wheel base recumbent or a long wheel base recumbent." Better is a very relative term. Many world speed records have been set with short wheel base recumbents and others with long wheelbase recumbents. Long wheel base recumbents have their applications, and some riders them "better".

I have chosen to build only short wheel base recumbents. I find that short wheel base recumbents have the following advantages over long wheel base bikes. They are simple. They are more maneuverable. They can use direct steering. They can have very short control cables. They can have very short brake cables or lines. They weigh less. They flex less. I outline each of these advantages after discussing the disadvantages below.

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Disadvantages of the short wheel base recumbent design.

There is one disadvantage to the short wheel base recumbent design, the "heel wheel problem". On slow, sharp turns, the front tire might rub on the heel of the shoe on the turning side. This can be startling, however to my knowledge it has never caused an accident. Whenever I teach someone to ride, I demonstrate where the tire can rub, and I teach simple remedies. Remember this problem only occurs on slow speed sharp turns. There is no danger of high speed mishaps because the wheel does not turn enough to contact the foot. At slow turns it is possible to turn the wheel sharply to maneuver around obstacles or to negotiate a trail, etc. When turning sharply, two primary techniques eliminate the problem.

The first technique "the point" is for turns not requiring power. The technique is to coast through the turn, with the turning side leg (right leg for right turns, left leg for left turns) pointing straight forward. In this position the heel of the turning side foot is far in advance of the tire. The other heel is back, but the front of the wheel is turning towards the opposite side of the recumbent, and consequently makes no contact. This works well for all coasting turns.

Often it is necessary or desireable to power through a turn. In this instance the technique "the lift" is to lift the heel of the turning side foot up and out of the way of the tire. The ball of the foot remains on the pedal, tilting the toe down and heel up to allow the heel to clear the tire, while still pedaling the crankset. This technique takes little practice, but requires remembering to perform it during slow, sharp turns.

If the rider forgets to use either technique during a slow sharp turn, the tire may hit the back of the heel, and may even pull the back of the shoe off the heel. This may be startling, but not dangerous. The rider is going slowly and can stop instantly to put the shoe back on. After several instances of hitting the heel, riders usually remember to lift or point.

Some riders do not want to deal with this issue at all. Instead a rain fender can be mounted backwards (the long side to the front instead of the back) on the front wheel. Then the tire does does not contact the foot, the fender does. Since the fender does not rotate, it simply pushes the heel reminding the rider to lift.

A second disadvantage with short wheel base recumbents is rarely applicable. During serious downhill recumbent mountain biking (going down rocky ski slopes), it is possible to shift too far forward and pitching yourself over the front of the bike (I haven't done this yet). During recumbent mountain biking in sand it is possible to stick the front tire, and pitch forward (I did this, then redesigned my front derailleur mount into a safety launch ramp). If you manage to drop your front wheel in an old drainage grate, you may pitch forward (I haven't done this, but it seems possible). This is less likely than on a recumbent than on a standard road bicycle, because the recumbent front tire is wider, and less likely to to fit through the grate slot. This is becoming less likely as these old road hazards are being replaced. Finally if you hit a huge pothole, it may be possible to pitch forward (I have hit my share of pot holes and haven't yet pitched forward, but it is possible). This can be alleviated somewhat with front suspension, but the best bet is to keep an eye on the road! During several emergency stops on short wheel recumbents over the years, I have thrown my body weight forward and dropped my feet onto the ground, while holding my bike up by the handlebars. I never was injured, and I did this only to keep the front chainring from contacting someone (who suddenly crossed the road etc) and cutting them. I do not recommend this technique, however in al my instances of doing this, I never pitched forward beyond the standing position.

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Simplicity in short wheel base recumbent design.

The underlying principle in my short wheel recumbent design is simplicity. The more complex the bicycle, the more margin for error and problems. If a simple system works well, making it more complex does not make it better. Many long wheel base recumbents were designed to alleviate the heel wheel problem described above. They are elaborate solutions to a minor problem. These solutions often create much greater problems than the one they solve. Some long wheel base models were also designed to give suspension to the bicycle. Suspension systems (suspension forks, and the rear shock) have outdated bicycle frame flex as a suspension system for recumbents.

There are many reasons to keep the various bicycle systems as simple as possible. Unfortunately it is not always possible (disc brakes are more complex than standard brakes, but they offer significant advantages), or the advantages of the complex system significantly outweigh the disadvantages of its complexity (suspension forks are another example). However when both systems are equal, the simple one is my choice. Simple systems generally weigh less, are more difficult to break, and are easier to replace or find a substitute for. There is a beauty in highly functional simplicity.

With short wheel base recumbent design, often what appears to be simple is not. A small change in bicycle componentry can make a significant change in performance. As an example many rear derailleurs do not have chain tension springs built to handle the significant chain weight that can be found on a recumbent bicycle. There are numerous options when faced with this situation.
1) Finding a derailleur that has adequate spring tension.
2) Changing the derailleur spring
3) Use a crossover drive to make the chain shorter and therefore lighter
4) Using a belt drive system
5) Making the bicycle front wheel drive
6) Using a lighter titanium chain
And this list could go on. Once the "simple" solutions have been found they often seem so apparent, however sometimes it is quite a journey to find them. In the example above, finding another derailleur may be easy if the right derailleur exists, is still made, and is in use enough that it is known. It becomes far more complex if it is rare, custom, no longer manufactured, and relatively unknown.

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Maneuverability in short wheel base recumbent design.

Sometimes maneuverability is not important, such as long straight runs. Generally however a more maneuverable bicycle is more versatile. I can ride my short wheel base recumbent on twisting dirt single tracks, through crowded festivals, up steep hills, through bicycle obstacle courses, and of course on all straight roadways. It can be like comparing a Porsche to a Cadillac. The Porsche can go anywhere the Cadillac can go, but the reverse is not true. Because of the high crankset, sometimes when I ride back trails, I don't even get the little velcro type weed seeds in my socks, because my feet are just above the grass line! Zig-zagging when I am going up a steep hill is a cinch whether it is an asphalt or dirt road. Since I am at a lot of mountain festivals, often the campsite areas were previously cow pastures, complete with huge holes and other obstacles. I have never had a problem maneuvering with my short wheelbase recumbent.

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Direct Steering in short wheel base recumbent design.

I consider direct steering to be a requirement. I have ridden recumbents with indirect steering and a number of problems emerged. The most common problem is play. Linkages create room for play. Even if the steering is solid when the bike is new, after the linkage has worn somewhat problems can emerge. With a good headset there is no opportunity for play on a bicycle with direct steering. Indirect steering must be accomplished with either a solid rod, or a flexible cable or chain. at each end of the rod cable or chain, there is room for play. If it is a cable or chain, the steering is accomplished by the pulling side. If it is a single rod, it is accomplished by either pulling or pushing. That rod can flex, bend or break, and the linkage connecting the rod to either the handlebar or the fork can flex bend or break. In either case that can spell disaster. Less than a year ago I was at a recumbent show where one manufacturer had about 20 bikes out for sale, all which had indirect steering that used a rod. I test rode his recumbent . I rode using the following standard recumbent riding practices.

When you are seated on a recumbent and not going anywhere, it is important to hold either the front or the rear brake. This keeps you from rolling backwards and falling over. Otherwise you legs slightly push you backwards, and after rolling a short distance, unless you grab the brakes and move you feet back, down you go. Because of this I teach new riders to hold the brake BEFORE sitting down when first getting on the bike. The "balance foot" stays on the ground to balance, while the "power foot" is positioned on the pedal that is pushed to take off. This is very similar to standard bicycle riding except that the power stroke is horizontal instead of vertical, so if the standard bicycle rider would ordinarily start pedaling with the right foot at the 1:00 position on a clock, pedaling clockwise, the recumbent rider would start with the right foot at the 10:00 position, exactly 90 degrees earlier. I teach riders to continue slightly holding the brake while positioning the power foot on the pedal, then to pedal backwards to position the pedal for maximum power stroke on takeoff, and to hold the brake until they apply enough pedal pressure to take off. Generally when you both hold the brake and apply pressure, the power leg is held in a state of readiness, and the moment you release the brake you move forward. This was not the case with the indirect steering recumbent I was testing.

Instead, as I applied slight pedal pressure, the rear wheel tried to push the recumbent forward, but because I was holding the front brake, the front wheel tried to keep the recumbent still. The tension was apparent, as I noticed the front wheel flopping back and forth slightly depending on how much pressure I applied. I released the pressure, then released the brake, then pedaled forward, when to my great surprise, the slightly turned wheel flopped completely around backwards! I let the bike slide back and the wheel straightened out. The steering rod had enough flex to bend, flopping the wheel, then bend back when the wheel straightened. I considered this to be a potentially fatal flaw: the wheel could flop backwards at high speed on impact with a rock in the road, with a pothole, or under other adverse conditions. In any case, once the wheel flopped backwards, the rider was going down!

I brought the recumbent back to the designer, showed him the problem, and he casually commented "Oh, the washers (at the end of the steering rod) are the wrong ones." I was amazed and dumbfounded. He had obviously seen this problem before and he was not concerned. (allow me to interject that I believe the vast majority of professional recumbent builders are far more conscientious than that designer was) The washers were not the problem, the design was. I have riden my recumbents at more than 50 MPH. I do not want my life balanced on washers, weak linkages or flexing rods. I want direct steering.

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Short control lines in short wheel base recumbent design.

With the advent of hydraulic brake systems brake cable length does not have to be a significant factor. It is however still a significant factor with any cable brake system. I want braking to be positive. I do not want my brakes to bottom out before stopping me. I do not want "cable stretch" to impact my braking at an inopportune time. I do not want brake cable housing slack to impact my braking. Both cable stretch and cable housing slack are created by long brake cables. The longer the cable, the greater the stretch. The longer the housing, the more slack. Some bikes I have riden had brakes where the lever bottomed out before applying adequate pressure. Keep in mind that both short wheelbase recumbents and long wheel base recumbents can attain very high speeds due both to the advanced aerodynamics and the "leg press" pedaling action. Stopping or not can be a life or death situation. There is no room for brake fading or brake failure. The short wheel base design in conjunction with under seat steering allows extremely short brake and control housings. Long wheel base recumbents that use above seat steering can have insufficient braking. Even with short wheel base recumbents that use above seat steering (which requires longer housing), you should consider hydraulic braking. Hydraulic braking also allows better "modulation" or brake control. Today I use only Magura hydraulic rim and hydraulic disc brakes. Allow me to repeat that. I believe strongly enough in braking, that I will not sell recumbent bicycles except with hydraulic brakes. This increases the cost significantly, but it is a very important safety feature on a high speed vehicle.

Shifting cables are a different story. While positive shifting enhances efficiency and makes the ride far more enjoyable, it does not create life and death events. Shorter derailleur cables certainly are better. Short wheel base recumbents with under seat steering have the shortest shifting cables, resulting in the most positive shifts.

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Frame flexibility in short wheel base recumbent design.

The longer the frame, the more flex it has. Before the advent of suspension, flexibility offered some degree of comfort. The longer wheelbase is less impacted by road roughness as the movement up or down (rock or pothole) is a smaller percentage of the overall base of movement (the wheel base) and consequently the overall up and down motion is more gradual when encountering obstacles or road roughness. The frame flex in conjunction with the longer wheelbase also adds to the comfort. It is back to the Porsche and Cadillac analogy. I have been riding unsuspended short wheelbase recumbents for over 17 years, without significant discomfort. Of course many road bike riders will tell you the same thing. A long wheelbase recumbent is bound to be more "cushy" than an equivalent short wheel base model. A full suspension short wheelbase model may be comfortable enough for most riders, but those with special needs for example recovering from back surgery, may need both full suspension and a long wheel base model. On the other hand a properly adjusted suspended short wheel base recumbent may be far more comfortable than an unsuspended long wheel base recumbent. Suspension offers protection not only for the rider, but it puts less stress on the frame too. After six months of riding my first purchased recumbent the frame flex started to wear on the frame, and eventually i broke that frame in six different places from over stressing it (it was considerably under built). Once I even folded the frame in half, from the pressure of the pedaling force unable to push the bike up a hill faster than the frame could collapse to bring the crankset closer to the freewheel!

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Frame weight in short wheel base recumbent design.

This is very basic. Short frames weigh considerably less than long frames. As the frame becomes longer the tubing must have larger dimensions or greater wall thickness to maintain the same strength. With riders willing to pay hundreds of dollars to shave a few grams off the weight of their bicycle, it makes considerable sense to lighten up the load by using less frame material if it is not needed.

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Short wheel base recumbent design summary.

Short wheel base recumbents are more maneuverable, lighter, and simpler than long wheel base models. With under seat steering have safer braking, better steering control, and more positive shifting. With suspension they are as comfortable as longer recumbents. Without suspension they are still far more comfortable than standard bicycles.