Life on Wheels (60 page)

The angle of your footrest hangers—the support that goes from the frame of the chair down to the actual footplate—determines where your feet will be in relation to your knees. A tight angle will put your feet more toward the knees than forward from the knees. Some footrests even angle backward, so that feet are farther back than the knees. A wider angle, of course, will bring your feet forward so that they are more forward, ahead of your knees. Which angle is best for you depends on a variety of factors, including leg length, physical limitations, and personal preference. The wheelchair order sheet is also likely to offer you the option of “tapered” footrest hangers. These angle inward toward each other and can help when you’re trying to turn in or pass through a narrow space. They also bring your feet closer together because the footplate width is narrower.

Recent designs have brought the angle of the footrests closer to the body, putting the legs into more of a perpendicular position. Table legs become less of an obstacle, removing the need for flip-up footplates for some people. A tighter footrest angle means a shorter “wheelbase” from rear to toe and, so, allows you to turn around in smaller spaces. You need sufficient range of motion to bend at the knees and ankles to use these closer footrest angles.

Some people like to be able to see their toes so they can tell where their feet are. If you are conscious of your posture and concerned about your feet being even and flat on the plates, you might want to choose a more forward angle. If you have long legs, you might choose a more-forward angle to bring your feet up away from the ground. This is an alternative to an even greater seat height, which can bring your knees too high to clear desks or tables.

For people with flexion contracture, in which the knee will not open to a 90-degree angle, the feet need to be supported underneath the leg. Some chair producers have an optional footrest that can be adjusted back underneath the chair. This is generally available only for manual chairs, since batteries and motors usually take up this space on power chairs.

The angle of the footplate itself can be either fixed or adjustable, raising or lowering your toes relative to your heels. The more forward the angle of the hanger, the more upward an angle the plate needs to be at to accommodate the natural posture of your feet. Most manufacturers offer an adjustable footplate as an option. This is especially useful for people whose feet are different, who go through changes with contractures in the legs, or who have progressive conditions that affect foot angle.

Tires influence the comfort of your ride and the amount of maintenance your chair will need. Some riders also consider the choice of tires an important aesthetic consideration. Generally, wheelchair tires are made of a gray rubber designed not to leave scuff marks on floors, as compared with the black rubber used for car or bicycle tires. Your choices range from pneumatic, air-filled-tires, to solid rubber tires, to solid inserts that replace the pneumatic tubes inside a tire. As you decide which type of tire will serve you best, keep in mind that larger tires will add width to your chair.

Pneumatic tires have inflatable tubes in them like bicycle tires, so they offer a more cushioned ride. Like bicycle tires, they can be punctured by a tack or piece of glass picked up on the street. The risk of punctures is greater for power chair tires because the extra weight of the chair against the pavement can help a sharp object pierce the rubber. Obviously, getting a flat tire means you might find yourself stranded away from home or going back for a repair, riding on the deflated tire. Riding on a flat tire can cause damage to the rim of the wheel. Flats can be minimized by using heavy-duty, thorn-resistant tubes or Kevlar tires. (Kevlar is a material used for bulletproof vests.)

Pneumatic tires must be kept well filled. Soft tires cause the chair to coast less, and that means more pushing for a given distance of rolling. This fatigues you sooner and puts more strain on your shoulders.

Pneumatic tires need replacement more often, since the depth of the rubber before reaching the fiber lining is thinner than that of a solid tire. The rubber wears down from normal use, particularly the more shallow treads of most manual chair tires. Knobby tires with a deeper tread are also available. They will last longer and provide better traction on unpaved surfaces but are harder on the hands of manual chair riders.

Thin-profile pneumatic tires—used on manual chairs when you expect to primarily travel on paved surfaces or in buildings with solid flooring— have less surface area in contact with the pavement, so there is less friction when turning. This makes the chair more agile, critical for sport use and preferred by some riders for daily use. The treads are substantially thinner, so if you plan to wheel on unpaved surfaces—or shoot baskets in the driveway, causing a lot of friction between tire and cement or asphalt—the thinner profile tires might not be for you. They also typically inflate to 100 pounds per square inch, so you need access to a strong pump or a gas station that goes up to that pressure.

Solid rubber tires make for a rougher ride. You will feel each bump of the pavement, but your tires will never go flat. You might value the security of knowing you will not get a flat, like this power chair user:

Many power chairs have solid tires with a deeper tread that lasts longer while providing better traction. Solid rubber tires tend to be slightly heavier than other options, since they contain more rubber.

A recent variation that is a compromise between pneumatic and solid rubber tires is a rubber insert. The insert is placed inside a tire as an alternative to an inflatable tube. The tire doesn’t need to be pumped up with air, so obviously it can’t go flat. Manual chair riders will find that the resulting apparent tire pressure is softer and that the chair won’t roll as easily. The wheels will also lose momentum faster, which means having to push more often—or burn up your battery charge sooner. However, some power chair users swear by rubber inserts, which continue to be improved in the efficiency of their ride.

Casters are the smaller wheels at the front (usually) of your wheelchair that allow the chair to turn. Casters rotate on their forks as you change direction in your chair. They can be large or small, soft or hard. The kind of casters you choose has a lot of impact on your comfort and mobility. You will want to weigh the advantages of small casters against those of large casters.

Small casters allow tighter footrest angles, thus the reason for their popularity on rigid frame chairs. Small casters are less likely to get in a position that prevents them from rotating when you turn. Greater agility has made small casters very popular, but, since they are hard—typically made of solid plastic or rubber—they make for a bumpier ride. Some smallcaster wheels are the same type as those used on rollerblades or skateboards. You will feel every crack in the sidewalk, you will need to lift the casters by doing a mini-wheelie to clear thresholds at doorways, and you must pay close attention on sidewalks for joints that are pushed up by tree roots or any other kind of change in the surface as you travel. They might get caught in a sewer or ventilation grate on the street. The smallest types of casters can even be stopped by very small obstacles, like a stone on a sidewalk. These kinds of sudden stops, as you know, can mean being thrown out of your chair.

Pneumatic casters are larger, at least six inches in diameter. They will provide a very soft ride. Any air-filled tire is at risk of being punctured, but it is also true that a flat caster will not strand you the way a flat main tire will. The chair itself will also last longer with larger, soft casters, as the vibration from harder tires causes more wear and tear on the frame.

Large casters can handle obstacles and rough terrain more easily. Picture a hard caster approaching a three-inch curb, and you can sense that it would require more force to roll over the curb than would a softer, larger tire. This is why frontwheel-drive power chairs typically have larger front, main wheels.

Before choosing a large caster, you’ll want to consider your ideal footrest angle. When larger, pneumatic casters are used, your heels must be moved forward with a greater footrest angle to clear the rotation of the casters, extending your overall length, “wheel to toe,” if you will.

Larger casters can also obstruct your movement suddenly if you are close to a wall or some other raised surface. As the caster begins to rotate, it becomes blocked by the wall, stopping your movement. You won’t be trapped; you’ll simply have to maneuver so that you get the caster free of the obstacle. Some people find this stressful, but many users learn to avoid these situations.

A compromise between the two extremes of caster options is the fourinch solid rubber caster. It cannot be punctured and is not stopped by small obstacles, but it does still transmit more vibration through the chair.

A manual wheelchair is more agile with smaller caster wheels. They also allow the footrests to come in closer—your heels have to be more forward to allow for larger wheels and the space they need to rotate around the vertical axle. Having your feet closer in means your overall length is reduced, so you can turn around in a tighter space.

But small caster wheels mean you can feel every little bump as you wheel, meaning cracks in the sidewalk, joints between paving tiles, or the cracks between floorboards. You can imagine that there are many surfaces you would wheel on that are anything but perfectly smooth. And if you’re a wheelchair athlete, you get banged around enough, so anything to absorb some impact is welcomed.

It was after seeing wheelchair rugby that Mark Chelgren decided to design a shock-absorbing caster fork for manual chairs, and Frog Legs were born (Figure 4-11). Integrating shock absorption into the caster fork makes it possible to use smaller, harder caster wheels and still have a soft ride. For some users, that has meant freedom from inflatable caster tires, which are always going soft and, sometimes, flat. Frog Legs are available for manual chairs and in a heavy-duty version for power chairs. They have been so popular that the major manufacturers have begun to offer them as options when ordering a new chair. Some have designed caster shock-absorption forks of their own, mostly for power chairs.

Figure 4-11 Frog Legs shock-absorbing caster forks
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One cautionary note: there are choices for how soft or firm the caster shocks are. If you go with something softer for a smoother ride, it will also mean that the caster fork will flex if you lean forward, for instance if you are picking up something from the floor. The chair could conceivably tip in this case, so take care to specify the caster forks properly.

Cars have shock absorbers to soften the ride, so, why not wheelchairs? This thought is occurring to an increasing number of chair designers. Outdoor terrain and vibrations from wheeling on sidewalks with all of their bumps and potholes have an impact on the tissues of the body. It is not good for us to be shaken up every day, so a soft ride is protective for people who encounter lots of vibration when they wheel. If you have back discomfort that is exacerbated by the bounce of your wheelchair, adding a suspension system can reduce the impact enough to spare you some back pain.

Several manual chair designs are based on shock-absorber designs, notably the Colours Boing and the Quickie XT. The manufacturers have worked with makers of shock absorbers for bicycles, engineering specialized shocks that address the specific kinds of forces and vibrations that are inflicted on a wheelchair and its rider.

As we’ve already discussed, one concern about rigid frame chairs is that they are less able to keep all four wheels in contact with surfaces that are not level, such as an outdoor trail or a city sidewalk with bumps and dips. This instability can mean a temporary loss of control, which potentially could be disastrous. Independent-suspension designs enable rigid frame chairs to have better contact with the ground.

Shock absorption is common to many power chair designs, especially those with independent suspensions. Heavy-duty outdoor power chairs particularly rely on shocks.

Spending the better part of the day—especially if you plan on a serious education, working full-time, or traveling—means that there is continuous pressure on certain parts of your body. Some people also have limited ability to remain in an upright position, at risk of fainting without intermittently reclining.