I was talking with a customer yesterday who is looking to purchase a new wheelchair. He likes the TiLite “Z” series but wasn’t sure about the differences between the ZR and the ZRa.
The ZR and ZRA are identical in every respect except one. The difference is the axle plate on the ZRA is adjustable whereas the ZR axle plate is not. With the ZRA you can adjust the center of gravity, and the rear seat height. These measurements can be hard to determine when ordering a chair because each person is different so there is no quick answer to which measurement is best.
Center of Gravity, and rear seat height are measurements based on individual comfort and function. The only way to really know if you’ve got the correct measurement is to try different settings and see which feels best. Without an adjustable chair you may have to spend 5 years in a less than optimal position before you can afford to get another chair.
With adjustable chairs like the ZRA it takes only about 15 minutes to move the center of gravity. The greatest part about adjustable wheelchairs is you get added function without sacrificing style or paying any more. I always recommend a chair that is adjustable because you can play around with those measurements as often as you’d like until you find the fit that is right for you.
You’ve spent months researching which new wheelchair you want to buy. You’ve considered the function, price, and style of many popular models, and have decided on a chair that best fits your needs. Maybe you’re going to go with the new TiLite Aero Z. Or maybe you are opting for a power assist chair like the Tailwind to give you that extra independence without sacrificing style. Now that you’ve decided you get to the order form and realize you’ve just begun.
Measuring a wheelchair can seem difficult especially for new wheelchair users. I know for me it was always difficult because I couldn’t afford to get the measurements wrong. Below is a guide that hopefully will clear up some of your questions.
While each manufacturer may have the measurements in a different order, or under slightly different names, the measurements are universal for all manual wheelchairs.
A. Seat Width – Measure from the outside of one leg to the outside of other leg at widest point. Generally the widest point will be at the hips. You then want to add an inch to allow for comfort. * Use the same measurement for cushion width when purchasing a cushion for your chair.
B. Seat Depth – Measure from the furthest back point of the users hips to the back of the knee, while seated in normal position. This measurement is then reduced, based on individual comfort, to allow space between the leg and seat cushion. The general rule is to reduce the measurement by 2” but this can vary for each user.
C. Front Seat Height – Measure the lower leg length (underside of the leg at the bend of the knee to bottom of heel with shoes on) and then reduce by the cushion height. Then add a minimum of 2” of clearance for footrest. If using a 4” cushion and your lower leg length measures 19”, then your front seat height would need to be a minimum of 17” (19 – 4 + 2). When choosing a front seat height it is important choose a height that accommodates transfers and allows users to easily fit under tables or desks. So while a 17” may be the minimum you may want a 21” front seat height for users to transfer into car. Be sure to compensate for seat cushion.
D. Rear Seat Height –The difference of front seat height to rear seat height is called “dump”. In a chair with 0” dump, or identical front and rear seat heights, the hips and knees will be parrallel. By lowering the rear seat height the users knees are raised above their hips by the difference. This can be an effective way of adding stability and ease of push for patients. Also being lower in the back puts the user closer to the ground which can be useful for picking up things off floor or low shelves.
E. Seat to Footrest –This can be the found by measuring the lower leg length and subtracting cushion height. Raising the footrest (reducing seat to footrest measurement) will raise users knees in relation to your hips which may help with stability but will, in general, cause the legs to bend out more as well.
F. Footrest Width – Measure from outside of one shoe to outside of other and add an inch for comfort. The feet should be spaced apart to user comfort and should be done using shoes that will customarily be worn.
G. Rear Wheel Spacing – This is the space between the seat frame and the rear wheel. Measure from the outside of the back post to the inside of rear wheel.
H. Front Angle – The front angle is the degree of bend from the top of seat frame to the floor. This measurement is the same as the degree of bend in the users knee in relation to their foot. For example a 90° front angle would mean your feet are perpendicular with your upper leg.
I. Seat Back Height – Measure from seating surface to the point in users back that is high enough to provide necessary support. Be sure to compensate for cushion height.
J. Seat Back Angle – This is the measurement of the back rest post in relation to seat frame. A negative angle would result in user leaning forward while a positive will result in a reclined position.
K. Center of Gravity – The center of gravity is measured as the distance from the center of axle tube (middle of wheel) to the front of the back post. This relationship determines the distribution of the user’s weight. Increasing the center of gravity (moving the axle further forward from back post) will increase the ease of pushing the chair. However, this does also increase the “tippyness” of the chair. There is a risk of flipping the chair over if center of gravity is too far forward. Decreasing center of gravity will make pushing harder but will make it less likely chair will tip over. A good rule for new users is to align the axle directly under users hips in proper seated position.
One other very important measurement to consider is the overall width of the chair. You want to ensure the chair isnt too wide to fit through doors around the house or at work. This measurement is done by adding the seat width, the rear wheel spacing and the width of wheels. A standard 24″ x 1 3/8″ wheel width handrims adds 6″ to overall seat width.