Questions About Wheelchairs/Components in General, and Specifically for TiLite Aero Z

[chasmengr]

When I needed to lower my RSH a bit more, my PT provided an adjustable cushion, and we adjusted the rear a bit thinner and the front a bit thicker: Comfort Company Standard Adjuster. I was able to lower my RSH about 1".



Switching from 25 to 24 wheels will likely decrease your pushing efficiency. It sounds counter-intuitive, but when you study the details, it's true:

The rule-of-thumb 'ideal' of fingertips touching your axle was derived from a research study (attached: Seat-Height propulsion effects highlighted.pdf) that identified the best elbow-angle range for pushing (ie., 100-130 degrees with good posture and hands resting top dead center on the push rims). Switching from 25 to 24 wheels will lower your RSH 1/2" and lower the top dead center of your push rims 1" because 24 wheels have smaller diameter push rims than 25". Thus your shoulders would be 1/2" farther away from top dead center of your push rims (in the pic 16-1/2 for 24 versus 16 for 25), increasing your elbow angle, which looks too obtuse already in your pics. Only accurate measuring of your elbow angles would reveal the facts.

[k4olin]

So I think what you're saying Chas is
A. based on where my arms are hitting... wheels should stay at 25"
B. based on where my arms are hitting RSH is correct or already lower than optimal
C. i should try to adjust my cushion to get the air to distribute lower in the back (i have a Varilite Evolution.. so i can let it air up and then sit down and let the air out some while really putting weight on my butt and not my legs to see if that helps.

[chasmengr]

A. yes.

B. No. I'm guessing from the fingertip-on-axle rule-of-thumb that your RSH should be lower, but measuring your elbow angle is the true indicator (100-130 degrees).

C. Maybe. Lowering your RSH by thinning the rear of your cushion (not changing wheel size) should be considered if your elbow angle is too obtuse (i.e., greater than 130 degrees). I doubt the Evolution will allow uneven inflation, but just letting air out may thin it all over; a folded towel beneath the cushion's front could then raise the FSH back up. (I have no experience with the Evolution.)

BE CAREFUL: I forget whether or not you're susceptible to pressure sores - be very careful if you are - consult a seating specialist - get mapped again with the thinner cushion. (I am not susceptible to pressure sores.)

[~Lin]

When I couldn't get my rsh lower, I went UP to 25" wheels. My reasoning was if I couldn't get any lower into the wheels, bringing the wheels higher up to me (relatively between the axle and my hand) would assist. I posted a few different times here with my theory, intially people disagreed later people agreed and after I went for it I was GREATLY pleased and will never go back to 24s. And in fact since then I've also seen others here on the forum make the same change for the same reason with good results. So definitely do not drop down in wheel size. While that drops your actual rsh, that makes the issue of wheel access for pushing efficiency WORSE. I've seen that happen to a member here, I can't remember her user name but her real name is Mimi. They dropped her to 22s because her rsh couldn't get low enough in 24s. Later, she got a new chair and went with 25s like I did and has been MUCH happier. You have to remember that the correct measurements are all for a reason, like rsh for pushing efficiency. Purely dropping rsh for the sake of dropping rsh without considering how it will affect your pushing efficiency is going in the wrong direction.

I also use a vicair cushion, the vicair vector myself and similarly much lowered the back and raised the height to increase my dump and get lower in the chair. I succeeded in getting as low as possible, probably 1" off the sling while being in the most comfortable cushion I've used so far, however I move around in my seat frequently, which shifts the air cells around so sometimes I have to lift myself up and punch things back into position or transfer out to reshape the cushion, because its made up of a bunch of different sections with individual air cells inside. I'm getting a stimulite pediatric cushion with my new wheelchair which I'm anxious to try out.

You can definitely try out lowering in the varilite and a towel in front. But yes if pressure sores are a concern you need to consider this! If it works and helps things out, you can purchase foam to raise the front of the cushion. Varilite I believe even sells a foam wedge, but its greatly overpriced. I'd get some firm foam from a sewing/craft or upholstery shop and cut it how you want (electric carving knife, or even kitchen knife depending on the type of foam and going slowly) and use some stick on velcro to attach it to your seat and cushion where you want it.

[WaveWolf]

Ive got the height set on the lowest possible setting. so there is no way I know of to change it. Though someone else may know of some kind of hack to lower it further.
But I agree. I sat in it with no cushion and bring that much lower felt better. So I may need to figure out something to keep most of my butt practically on the seat webbing but angled up to keep the knees higher.
Otherwise im guessing I'd have to change from 25" to 24" tires. Which isn't in the budget right now.

The measurements must have been quite off as it was originally set about 2.5-3" higher than where it sits right now.



Handrim wise. I think the problem is my instinct is to fully grab that wrapping my fingers all the way around them. So then I often get them squished when one of the hand rim tabs comes up while I'm trying to initially grab the spinning wheel.

Really nice looking chair!!! And so good that you are able to make the adjustments. From my limited experience, I am surprised that 25" wheels were ordered for you. I was told that fingertips should easily touch QR button, and yours are significantly above. Perhaps someone who is in the opposite position would trade parts with you?! I think the Natural Fit handrims would be far more safe for you if you are bashing your thumb or fingertips.

chasmengr, you seem to know a great deal about these things and I really appreciate your posts!

[chasmengr]

chasmengr, you seem to know a great deal about these things and I really appreciate your posts!

Thanks. I am very blessed too have had a long AB career in construction and engineering before becoming medically disabled. I really appreciate that I am still able to share my past training - I am unemployable now, and love to share here when I can.

[~Lin]

From my limited experience, I am surprised that 25" wheels were ordered for you. I was told that fingertips should easily touch QR button, and yours are significantly above. Perhaps someone who is in the opposite position would trade parts with you?!

Might want to take a look at my post above yours