A wheelchair that is too narrow or too wide can cause discomfort. When too narrow, a wheelchair can become restrictive and increase the likelihood of pressure sores, while when it's too wide, becomes more difficult to push due to the angle of the arms from the shoulders to the wheels.

To determine the necessary seat width, measure the rider's widest area of the body and add one inch. This will allow for optimum seat width while maintaining ideal usability, comfort and safety.

To determine the appropriate seat height, measure from the bend of the knee to the bottom of the foot. Subtract the height of the seat cushion if one is being used. If the wheelchair is not being self propelled by the feet, also add about 2 inches to allow for foot clearance.

A chair's rear seat-to-floor height is most commonly set at a height 1" lower than the front seat height.

The rear of the seat is generally set at lower height than the front of the seat to prevent sliding forward.

When armrests are not fitted properly the wheelchair can become more difficult to push. Not all armrests are adjustable. Height should be fitted to allow the forearm to rest fully on the armrest without pushing up on the shoulders. For users who sit at a table or desk, swing-away armrest can beneficial.

There are four basic types of armrests:
1. Full length, fixed height (entire armrest is padded with a non-adjustable height)

2. Full length, adjustable height (entire armrest is padded with various height seetings)

3. Desk length, fixed height (partial armrest is padded for easier access with tables, non-adjustable height)

4. Desk length, adjustable height (partial armrest is padded for easier access with tables, various height seetings)

Armrest that can be easily removed or flip up and down gives users the choice of when to use the armrests.

There are two types of rear wheels, Spoked Wheels and "molded" Mag Wheels.

1. Spoked Wheels are made of metal and are similar in appearance to that of bicycle wheels. The number and size of the spokes affect durability, shock absorption, weight, and performance. The more spokes, the more stable the wheel will be.

2. Mag Wheels are made of molded plastic or a composite. They have a small number of wide molded spokes that are an integral part of the wheel. Mag wheels are more durable, require less maintenance, and usually weigh more then spoked wheels.

1. Pneumatic (air-filled) tires provide a softer ride, but need to be kept inflated. Because pneumatic tires are softer than urethane tires, they are harder to push, with more resistance to the shoulders.

2. Pneumatic Flat Free (foam-filled) tires provide a stiffer ride compared to air-filled tires, and will never go flat.

3. Urethane (solid, flat-free) tires provide the quickest and stiffest ride. And they will not go flat.

Tire Tread also affects the wheelchair ride. Tires with very little tread offer a quicker ride and turn more easily because there is less rubber in contact with the ground, causing less friction. "Knobby" tires with deep treads are helpful on unpaved and rougher surfaces, yet offer less maneuverability. A 1 3/8" treaded tire is a good basic tread for everyday use.

Casters typically come in sizes from 3"" to 8"". The smaller the caster the better the maneuverability of the chair and the less likely it is to shimmy. But smaller casters on unpaved surfaces, riding in and out of elevators, or passing over street grates can be more problematic. Smaller casters are typical of chairs used for sports like basketball, which is played on an even, hard surface, yet their maneuverability makes them popular for everyday use. 3"" casters require the most riding skill and may not be the best choice for a first time wheelchair user.

The large 8", pneumatic (air-filled) caster provides the softest ride and easily rolls over bumps and raised surface, yet makes propelling the chair more difficult. Because of their size, 8"" casters can be an obstruction coming into contact with furniture or the rider's foot. Pneumatic tires need to be kept inflated with the correct pressure, and are capable of going flat.

4" to 6" casters offer a good combination of maneuverability, performance and ease of riding over surface obstructions. Composite (airless) casters offer better durability and quicker ride, while pneumatic casters provide a softer, slower experience.