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Thread: Sitting lower: add more dump or bigger rear tires

  1. #11
    Quote Originally Posted by Brianm View Post
    No, I am looking at gaining 0.5" of reach, hence going from 16" in the rear to 15.5" or a 25" wheel, which will in affect give me the 0.5". Dump will not be decreased with the 25's because the chair would be built with that in mind.
    Sorry, I wasn't too clear in my post - yes, you'll be gaining .5" dump, but not an 1", like I assume you want, hence my saying you'll be decreasing the goal of 1" gain, to .5 (thus, the statement 'decreasing .5" in dump')

    So, are the measurements you plan to have built, with the 25" wheels in mind are as I've asked earlier? The reason I specifically listed them as I did was based on the measurements you listed as wanting, and since you keep saying x "or" y, I assumed your option for 20f and 15.5r would be with keeping wheels at 24" and if you went with 25" wheels, your measurements would be 20f and 16r.

    Could you clarify?
    Quote Originally Posted by chick View Post
    So, you want 1" more dump, correct?

    And your options are
    20f and 15.5r and 24" wheels OR 20f and 16r and 25" wheels?

    If you go with 20 f and 16 r, and get 25" wheels, you're actually decreasing .5" in dump. You will be sitting higher off the ground and will gain .5" more arm reach into the wheel while sitting into the wheel that much more.

  2. #12
    Senior Member jschism's Avatar
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    Quote Originally Posted by Brianm View Post
    I can't lower the front because my foot clearance is less than an inch now, hence going higher in the front.
    so, I'd say probably a 25" wheel is what you want. You must be fairly tall or long legged. These wheelchair companies should have a a chart that indicates people over a certain height should try the bigger diameter wheel. I have this crappy italian chair with 25's and a 18" RSH, and even that has a really short stroke/push of the wheel cause it sits too high and you just don't have enough wheel to grip and turn.

  3. #13
    I assumed your option for 20f and 15.5r would be with keeping wheels at 24" and if you went with 25" wheels, your measurements would be 20f and 16r.
    Correct. In my current chair, if I was a half inch lower I would have better reach on my wheels, getting closer to the center of the hub with my reach. This has been my plan. I am concerned about the amount of dump I would have so I am wondering about 25" wheels and staying at 16" RSH.
    C5-6 Complete - 8/13/1982

  4. #14
    Quote Originally Posted by jschism View Post
    so, I'd say probably a 25" wheel is what you want. You must be fairly tall or long legged.
    I can't say specifically on my height, but estimate at 6' 2".
    C5-6 Complete - 8/13/1982

  5. #15
    Senior Member ~Lin's Avatar
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    Quote Originally Posted by jschism View Post
    looks like you could lower your seat heights another inch, you want your finger to be about the middle of the quick release button, looks like your just a little higher than that.
    What are the consequences when your finger isn't around the middle of the quick release button? I've been meaning to get some photos of me in my chair and post asking about that. Now that I'm remembering again I'll try to get that today or tomorrow...

    I think my hands are pretty far away from the middle of the wheel. I'm not entirely sure since I'm going by feel and not able to look at myself. I've wondered about what the difference is when you don't fit the chair that way. But I also started thinking about the youtube video JeffAdams made showing the difference between transferring from the lower wing of the icon and how thats better for your shoulders. So I thought maybe having the pushrims lower might be better for my shoulders? But in this thread it sounds like being lower (higher pushrim) gives you further reach, which means going further with each push and therefor better for the shoulders?

    I have 2" of dump now and have been thinking about increasing it because I have some difficulty carrying things on my lap. I'm concerned about my hips hurting from the more closed angle though.
    I am not paralyzed. I have a genetic connective tissue disorder called EDS with neuro complications.

  6. #16
    Senior Member SCI_OTR's Avatar
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    Is it even possible to do 25" wheels with projections?

    If so, I would verify that the projection rim being sold as a 25" version isn't just the 24" version with different mounting hardware.

    25" wheels would mean less clearance during transfers-especially with a shorter frame.

    On the other hand 4.5" is a lot of seat slope is over 16".

    Then consider you are going to lose a tad bit of seat depth with an ADI back and lose any sag in your back upholstery that may be increasing your effective seat depth. I would definitely get the Schulte Dimension, subtract 3/4" to account for the back, and compare it to the SD you get off your current chair.

    I think the "center of the hub" rule also goes out the window when you use projections. It's more whether or not you feel you are getting optimal leverage. With 24" wheels, that may mean 15.5"--or even lower.

    Have you contemplated surgical resection of 1-2" of your tibia & fibula in each leg? A shorter lower leg length means a lower front STF height and the ability to attain a 15" to 15.5" rear STF height with less dump.

    That is truly a difficult question to decide. One that you may want to contemplate until the TR Series 2 comes out.


  7. #17
    Senior Member SCI_OTR's Avatar
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    Quote Originally Posted by jschism View Post
    These wheelchair companies should have a a chart that indicates people over a certain height should try the bigger diameter wheel.
    Why? It would be about as useful as a chart classifying wheelchairs by HCPCS codes. Rear seat height, rear axle location, cushion thickness, and CAFT* all need to be considered.


  8. #18
    Senior Member SCI_OTR's Avatar
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    * Clearance Area for Transfers


  9. #19
    Senior Member feisty's Avatar
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    Quote Originally Posted by ~Lin View Post
    What are the consequences when your finger isn't around the middle of the quick release button? I've been meaning to get some photos of me in my chair and post asking about that. Now that I'm remembering again I'll try to get that today or tomorrow...

    I think my hands are pretty far away from the middle of the wheel. I'm not entirely sure since I'm going by feel and not able to look at myself. I've wondered about what the difference is when you don't fit the chair that way. But I also started thinking about the youtube video JeffAdams made showing the difference between transferring from the lower wing of the icon and how thats better for your shoulders. So I thought maybe having the pushrims lower might be better for my shoulders? But in this thread it sounds like being lower (higher pushrim) gives you further reach, which means going further with each push and therefor better for the shoulders?

    I have 2" of dump now and have been thinking about increasing it because I have some difficulty carrying things on my lap. I'm concerned about my hips hurting from the more closed angle though.
    this is a great question. I'm wondering if getting further down in my chair will give me a longer stride in my push, bc I feel like I make tons of short pushes due to my inability to really reach alot of the wheel. does lowering your ass allow you to reach back further in your push?
    An administrator made me remove my signature.

  10. #20
    Quote Originally Posted by SCI_OTR View Post
    Is it even possible to do 25" wheels with projections?

    If so, I would verify that the projection rim being sold as a 25" version isn't just the 24" version with different mounting hardware.

    25" wheels would mean less clearance during transfers-especially with a shorter frame.

    On the other hand 4.5" is a lot of seat slope is over 16".

    Then consider you are going to lose a tad bit of seat depth with an ADI back and lose any sag in your back upholstery that may be increasing your effective seat depth. I would definitely get the Schulte Dimension, subtract 3/4" to account for the back, and compare it to the SD you get off your current chair.

    I think the "center of the hub" rule also goes out the window when you use projections. It's more whether or not you feel you are getting optimal leverage. With 24" wheels, that may mean 15.5"--or even lower.

    Have you contemplated surgical resection of 1-2" of your tibia & fibula in each leg? A shorter lower leg length means a lower front STF height and the ability to attain a 15" to 15.5" rear STF height with less dump.

    That is truly a difficult question to decide. One that you may want to contemplate until the TR Series 2 comes out.
    Getting correct projections for 25" wheels has been a concern of mine, but I have swapped some emails and it appears to not be a problem. The form I fill out is very detailed in the dimensions, they are custom made and "yours" once made. They do ask about wheel size and brand as well as center-to-center dimensions, among other things. So excellent question and I do believe they will be made as needed.

    I will see about getting the Schulte Dimension, if the insurance ever comes through! I forgot about transfers; I suspect I can work around it, I just need to scoot down further. I did have the ADI back on my current chair for a (very) short time, wishing now I had more time with it.

    While I have better reach to my projections than my previous chair, I can tell I'd be better served if I was down a bit lower.

    Surgery, you are scaring me!

    What do you know about a series 2?
    C5-6 Complete - 8/13/1982

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