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What. Size wheel do you prefer and why?

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  • slow_runner
    replied
    That bike shops (tyre manufacturers) are inconsistent in their inch sizing is why we should only heed the ETRTO sizing. The ETRTO is without variance, it is the international standard.
    https://www.etrto.org/About-us/ETRTO
    559 tyres are never far away; as for the correct tubes, high pressure, they are easy enough to carry as a spare. These days, good quality tyres are well protected from puncture.

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  • nauticalmike
    replied
    Has anyone else noticed that bike shops are inconsistent on what the inch equivalent is for the 559 wheelchair wheels? The tire manufacturers are not consistent either. I have some kenda 559 knobby tires that work on my 559 rims, but the sidewall says 26x the width, which I don’t recall with any certainty At the moment, I think like 2 or 2 1/2, but then in another location Around it’s sidewall it also says that it is a 559. I am also surprised by everyone’s statements that they are commonly stocked at bike stores, because although I do have a bike store that stocks them now at my request, they didn’t previously. Also trying to find 25x1 inner tubes is often difficult because in my experience they are not really all that common, especially at stores that sell bikes, but that are not bike stores, like Walmart or target, or the now defunct k-mart, actually at these stores you can pretty much forget about finding anything 25”. If you are lucky they may carry a 25” x 2 because mountain bikes seem to use those frequently. Sorry I kind of went off on a tangent here...

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  • slow_runner
    replied
    Originally posted by pfcs49 View Post
    @Oddity: IMO the acceleration of the wheel/tire's initial moment is insignificant. Imagine your wheel in air in front of you. Spin it up to rolling speed with one finger. The torque required is so small that it makes you want to move nearer the hub and give it a 20mph++ spin to see how fast you can get it going! ...............
    I recall when I was a child I enjoyed to play about with the gyroscopics of spinning a wheel in the horizontal. It was a revelation to find that such a large item could be balanced on one finger and with increased speed it became 'lighter' and could be moved from the horizontal plane for a few degrees. I thought, "No wonder spaceships were disc shape"

    Originally posted by Oddity View Post
    .......Bottom line for me: tire pressure is where it's at for pushing efficiency. Size matters (huh huh huh), and is notable when comparing between them, for me, but it's nothing compared to the effects of tire pressure!
    Yep I agree and jokes aside and included. No matter the size, if it cant be inflated to the correct pressure, all you have is a frustrating experience.
    25" and 110psi for me - my compressor wont pump much over 110 and I cant be blowed making the adjustment.

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  • pfcs49
    replied
    I certainly can agree on tire pressure! Every time I top up my tires is like losing 10 years of age!

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  • Oddity
    replied
    I think when we put that wheel onto the ground and add 100-200lbs to the initial moment, then it begins to matter. Like I said, whether it *really* matters, in terms of repetitive stress or pushing, I don't know, but I CAN feel it. If I can feel the difference, then that is enough for me to care about it, without any other specific knowledge or info.

    I get the "inches" of a push, but that's not the measurement that really matters. Wheel speed is where the differences can be calculated, in RPMs. E.g. A 27" wheel rolling one complete R moves (27*3.14) 84.78". A 25" wheel moving one R moves (25*3.14) 78.5". The 27" wheel takes more energy to complete one R, in exchange for more motion. The trade off ratio is equal, more or less, to the distance benefit, mathematically speaking (and laws of thermodynamics speaking), with tons of other variables adding to the equation not accounted for here! It mostly comes down to the amount of energy to maintain a certain RPM, not the "distance" of each push, which is technically also different with partial rotations!

    Bottom line for me: tire pressure is where it's at for pushing efficiency. Size matters (huh huh huh), and is notable when comparing between them, for me, but it's nothing compared to the effects of tire pressure!

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  • pfcs49
    replied
    @Oddity: IMO the acceleration of the wheel/tire's initial moment is insignificant. Imagine your wheel in air in front of you. Spin it up to rolling speed with one finger. The torque required is so small that it makes you want to move nearer the hub and give it a 20mph++ spin to see how fast you can get it going!

    Also, let me repeat what other have said, the mechanical advantage, hand to surface is the same irregardless of diameter; a 6" push will move the chair 6" no matter what tire is in the middle.

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  • Oddity
    replied
    I don't believe the push physics are the same between different sized wheels.

    The moment of inertia (needed to overcome to get rolling) is higher with larger diameter wheels. It requires more energy (torque) through the axis to get a larger wheel rolling to a given wheel speed (RPM) than a smaller one.

    The trade off for this increase in energy requirement to get going is a farther roll. A small wheel vs a larger wheel spinning the same RPM will not go as far as the larger wheel over the same amount of time.

    A key factor for consideration re: pushing a wheelchair is that we are more often over coming moments of inertia than we are constantly maintaining a given wheel speed (since our energy comes in 'pulses', between which the moment of intertia rebuilds, up to its max when we stop.) This means we are affected by the increased energy requirements of a larger wheel more often than we benefit from its greater rolling efficiency, generally speaking.

    Larger wheels have other desirable attributes, especially on less than perfectly smooth and clean surfaces, but the physics of getting them (and keeping them) moving aren't the same as smaller wheels.

    Whether the differences are large enough to matter, over time, is an open question. For me, any difference that I can easily feel at the wheel is a difference that matters.

    Of course, the biggest obstacle most of us face, day in and day out, IMO, when it comes to the efficiency of our push strokes, is: not keeping our tires inflated enough!!

    (Push rings being the same distance from the outer diameter of tire means the ratio between input energy and output rotation will be the same, between the sizes, but the amount of energy needed is still greater for a larger diameter setup.)

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  • NW-Will
    replied
    So many variables.. your size, and how much dump you want, how close to the axle your butt will be etc. and then how comfortable your push stroke is with the various wheel sizes.

    Just like bicycles the larger the wheel the easier the roll.
    The physics of the push is the same, as the pushrim is generally the same distance from the edge of the tire(where it touches the ground) no matter what size you go with, it has more to do with the mechanical comfort action of your shoulder, elbow and arm length to achieve the most efficient push.
    And then just your personal preference.

    As folks have mentioned 25"(wheelchair size wheels) 559 have by far the best selection of tires.

    I started out with 26" 590's and you pretty much have 3 tires to choose from, similar problem with the 24" 540's

    I'm 6" and ended up with 25" 559's with balloon tires that achieve the same outside diameter as 27" 622's, I can easily swap out my 25" wheel tire combination for my 27" wheel tire combination without having to adjust anything (brakes CoG etc.). With maximum dump I get 15.5" rear seat height to ground.

    Then put my 26" natural fits on my 27 622 rims. works good for me.

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  • fuentejps
    replied
    I've always ran 24s because I'm a tall guy and I like my chair to sit low makes it easier to get under tables and things like that I try 25s twice and it always raised my height, so I was cracking my knees on tables

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  • Oddity
    replied
    25" (559) for me. I picked it because it was in the middle of the 3 common sizes, and just stuck with it over the years. I've tried the others since, and noticed: 590 were noticeably harder to GET going and 540 needed to be pushed a lot to KEEP going.

    I think I lucked into the right pick, 15 years ago, before I knew anything about wheelchairs.

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  • pfcs49
    replied
    I run 24". Super easy to change, available everywhere, and any thing larger, a pair would not fit in the passenger's footwell of my GTI!

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  • funklab
    replied
    Originally posted by slow_runner View Post
    I heard that the 559 tyre size was more available at bike shop
    this is the reason I switched from 590. Was out of town for school and a marathon I’d just installed kept slipping off the rim (I probably overstretched it trying to install). I had to get a tire if some kind, went to or called every bike shop open in my city that weekend nobody had any tire that would fit that rim. I had to pay for overnight shipping of a tire ($90 for the shipping iirc) and I was stuck inside for two days until the shop got the tire and I could have them install it.

    While I was in the shop I asked them if they had any 559 tires that would fit a 1 inch rim. They had several.

    So now I run 559s. The 590s were nice, a little more efficient on long pushes and definitely easier to hop up curbs, but turning radius is a tad wider. None of that makes a serious difference if you really really need a tire right now though.

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  • slow_runner
    replied
    559s here. Reason? I am used to them - they feel right (that I am longer in the body could have a bearing on it) - I heard that the 559 tyre size was more available at bike shop and there were a better choice of tyres. Having said that, I always run RightRuns on my rims.






    not

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  • nauticalmike
    started a topic What. Size wheel do you prefer and why?

    What. Size wheel do you prefer and why?

    I am just wondering what the perceived advantages are between 24”, 25”, and 26” wheels and tires on a wheelchair are. Are 24” wheels actually easier to push? Are 26” wheels faster? etc...
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