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

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  1. #1

    Sitting lower: add more dump or bigger rear tires

    As many may recall, I made some big changes from my previous chair to my current chair, see below. One big change is that to get me lower in the wheels I added an inch of dump, where I currently have 3.5" of dump, really 3.75" with the caster in the bottom hole. RSF is 16" and FSF is 19.5" (19.75").

    In my next chair I desire to be down into the wheels a tad more. I already plan to have the FSF at 20", so this will add even a bit more dump than I currently have. To get me a little more into the wheels I would like to run it by the collective wisdom here on thoughts to drop the RSF another 0.5" to 15.5" or to go to 25" rear wheels instead of 24"?

    Here is a list of the changes I am looking at:

    * Going from 19.5 front (really 19.75 with caster in bottom) by 16 rear to 20f and 15.5r or 25" wheels

    * Regular forks with 5x1.5 instead of FL forks and 4x1.5

    * 85 degree front instead of 80

    * +0.75" frame instead of +1"

    * Standard footrest instead of flip back footrest

    * ADI solid back

    * 4 degrees of camber instead of 2
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    C5-6 Complete - 8/13/1982

  2. #2
    Senior Member brian's Avatar
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    Love the McIntosh in the background.

  3. #3
    You look pretty comfortable with 80 degree front. Your legs are pretty straight up and down. I was thinking of going from 85 to 80 to get my legs more straight up and down. Even with your 80 my legs would prob still be back a little since I like to put the tips of my shoes on the end of the footplate, not much hangover. I feel just too crunched up in my 85 the way I sit. I go from pc to mc so much I can't get comfortable in either. MC is like sitting in a spoon and pc is like sitting in a tank.

    4" dump is my sweet spot too. I don't think we, or I, get the full affect of the measured dump anyway because it seems we don't sit as far back in the seat in a mc with dump, so that may be taking an inch or so of sitting dump away? Then that leaves not as much cushion to sit on. My mc has a 16" seat depth and my pc has an 18" seat depth and my knees have the same amount of clearance behind to the seat pans. This is why in a mc I feel like I am forward too much like sitting out on a perch kinda, hence why I want to sit lower in the tires also for that cocoon affect. All of this is addressed in my prototype, like sitting in a sports car.

    Is there any particular reason why you want to get away from an 80?
    Life's perceived journey in this PMR is not to arrive at the grave safely in a well preserved body, but rather to skid in sideways, totally worn out, shouting "holy **** what a VR ride!"
    Pete C6/'97

  4. #4
    Senior Member jschism's Avatar
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    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.

  5. #5
    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.
    I can't lower the front because my foot clearance is less than an inch now, hence going higher in the front.
    C5-6 Complete - 8/13/1982

  6. #6
    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.

  7. #7
    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

  8. #8
    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.


  9. #9
    Is there any particular reason why you want to get away from an 80?
    If I didn't have the +1 in my frame I would be perfectly happy with the 80 degree, in fact, visually I would prefer my chair without any extra frame and going with 80 degrees, but I use that extra frame in transferring. In the pictures supplied I have my calf strap on my chair, but I removed it some time ago, and my feet are further back and frankly I believe they are sitting where an 85 degree front would set.
    C5-6 Complete - 8/13/1982

  10. #10
    Quote Originally Posted by Brianm View Post
    As many may recall, I made some big changes from my previous chair to my current chair, see below. One big change is that to get me lower in the wheels I added an inch of dump, where I currently have 3.5" of dump, really 3.75" with the caster in the bottom hole. RSF is 16" and FSF is 19.5" (19.75").

    In my next chair I desire to be down into the wheels a tad more. I already plan to have the FSF at 20", so this will add even a bit more dump than I currently have. To get me a little more into the wheels I would like to run it by the collective wisdom here on thoughts to drop the RSF another 0.5" to 15.5" or to go to 25" rear wheels instead of 24"?

    Here is a list of the changes I am looking at:

    * Going from 19.5 front (really 19.75 with caster in bottom) by 16 rear to 20f and 15.5r or 25" wheels.
    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.

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