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difference in diameter better 24inch(25-540) and 26inch(25-590) wheels

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    difference in diameter better 24inch(25-540) and 26inch(25-590) wheels

    if you calculate it based on the circumference and rounding the number it would be

    (26inch) 590 / 3.14 diameter = 187mm
    (24inch) 540 / 3.14 diameter = 171mm

    Or using the online calculator https://www.omnicalculator.com/math/circumference

    Anyway I need to know because I'm ordering a new chair and need to adjust my front frame and rear frame heights based on the difference in height of the wheels.

    A difference in height of 16mm seems too small from what I can remember when seeing both sizes together but I could be wrong.

    If anyone knows let me know?

    Thanks,
    Rob

    #2
    187mm = ~7.4 inches. Not sure what you're trying to work out there? Circumference is diameter multiplied by pi.

    it's my understanding that the 590, 559, 540, etc. is the diameter of the rim.

    25.4mm in an inch, so the difference in diameter is ~2 inches from a 24" to a 26" wheel. (which seems logical?)

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      #3
      Keep in mind that difference in diameter number is only half when applied from the axle to the ground.

      Comment


        #4
        I think 540/590 is the diameter of the rim, you then need to add the tyre height which is usually a % of the width. That isn't an easy number to find.

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          #5
          Not sure of the exact question, but for every 1" diameter difference you'll only get .5" of ride height difference. Important when trying to figure out ride height difference based on diameter differences,
          "I have great faith in fools; self-confidence my friends call it." - Edgar Allen Poe

          "If you only know your side of an issue, you know nothing." -John Stuart Mill, On Liberty

          Comment


            #6
            Originally posted by mrb View Post
            I think 540/590 is the diameter of the rim, you then need to add the tyre height which is usually a % of the width. That isn't an easy number to find.
            Yes. Use inches. 590 is the rim. 590 mm = 23.2 inches.
            I have had periodic paralysis all my life. I lost my ability to walk in 2011 beginning with a spinal block, which was used for a hip fracture caused by periodic paralysis.

            Comment


              #7
              I will also add that if the intent is to change from a 24" wheel to a 26" wheel (assuming the same center-of-gravity setting) you will not be as nimble in tight spaces, ie. washrooms. That extra inch behind you doesn't sound like much but it's actually a lot when trying to back over a toilet to get the door shut or even in a smaller apartment-style kitchen trying to turn around between the 2 countertops/cabinets.

              Comment


                #8
                Thanks for the replies.

                Jeez I just did those calculations without thinking haha! Yeah I had thought the 590 and 540 were the circumferences, when they are obviously the diameter!

                But the diameter from from the rim to rim because 590mm is only 23inches?

                Am I right in thinking the difference in wheel height between 26inch and 24inch is 50mm?
                This is what I had originally thought before doubting myself.

                I am moving from 26inch wheels to 24inch wheels, so it should be easier to manoeuvre.

                My front frame height in my current chair is 490mm and the rear frame height is 420mm, with 26inch wheels.

                For the new chair with 24inch wheels, I don't want to sit too much lower, but still have much the same pushing position.

                Between the 24inch and 26inch wheels there is a 50mm difference in height, yeah?

                I was thinking with the 24inch wheels a front frame height of 465mm and a rear frame height of 395mm. Both frame heights reduced by 25mm.

                So, for the new chair, by reducing my frame height by only 25mm for the new frame, instead of the 50mm difference in height between the wheel sizes, the distance between my shoulder height(sitting in chair) and the top of the wheel would be 25mm longer than the distance between my shoulder height and the wheel with my current set up.

                I know I have explained this badly, but if you get what I mean, is that correct?

                Thanks,
                Rob

                Comment


                  #9
                  Originally posted by rob1 View Post
                  ...For the new chair with 24inch wheels, I don't want to sit too much lower, but still have much the same pushing position.

                  Between the 24inch and 26inch wheels there is a 50mm difference in height, yeah?...
                  I may be a bit confused by your question, but here goes:
                  1. You will sit 1 inch closer to the floor since the diameter of the wheel is one inch less.
                  2. Your shoulder to axle distance will be the same since it is independent of the wheel size.
                  3. Your shoulder to tire distance will be 1 inch more since the wheel is smaller, that is the top of the wheel is 2 inches closer to the floor but your shoulder is only 1 inch closer.

                  But if you are ordering a chair, is any of this relevant? Don't you do this by FSH, RSH, dump, and wheel size? Just keep the first three the same as you have now.
                  I have had periodic paralysis all my life. I lost my ability to walk in 2011 beginning with a spinal block, which was used for a hip fracture caused by periodic paralysis.

                  Comment


                    #10
                    To muddy it further??.
                    AFAIK. 540, 559 etc relates to the bead set diameter, so not actually the rim diameter. I run Spinergy 559 and have some 540. If you wish I can supply you with the diameter of these wheels running Schwalbe Right Runs/Marathons.

                    If you intend to use the same tyres; to determine the difference in ride height, just add or subtract half the difference between your existing wheel-set and what wheel-set you anticipate purchasing.
                    I don't bother converting from ITRTO to inches; metric is far simpler to work with.

                    Are you looking for increased ride height or gain distance per revolution?
                    Ride height is easy enough to calculate; circumference will depend on your tyre choice.
                    Last edited by slow_runner; 27 Jun 2019, 8:27 PM.

                    Comment


                      #11
                      hey, slow_runner yeah that would be useful if you could tell me the diameter of the 540 running Schwalbe Right Runs/Marathons?

                      Can anyone confirm the difference in diameter between a 26inch(25-590) wheel and a 24inch(25-540) wheel both running Schwalbe Marathons is 50mm?

                      I measured my 26inch(25-590) wheel running Schwalbe Marathons and from the floor to the top of the tyre it is 650mm. I would like to confirm what the measurement of a 24inch(25-540) wheel running Schwalbe Marathons is from the floor to the top of the tyre?

                      I should probably make it a clear question. If your front seat height is 490mm and your rear seat height is 420mm and you have a 26inch wheel and you were getting a new chair with 24inch wheels and wanted to keep the same pushing position, how much would you have to lower your front and rear seat height?

                      Thanks,
                      Rob
                      Last edited by rob1; 28 Jun 2019, 11:20 AM.

                      Comment


                        #12
                        hey, slow_runner yeah that would be useful if you could tell me the diameter of the 540 running Schwalbe Right Runs/Marathons?

                        Can anyone confirm the difference in diameter between a 26inch(25-590) wheel and a 24inch(25-540) wheel both running Schwalbe Marathons is 50mm?

                        I measured my 26inch(25-590) wheel running Schwalbe Marathons and from the floor to the top of the tyre it is 650mm. I would like to confirm what the measurement of a 24inch(25-540) wheel running Schwalbe Marathons is from the floor to the top of the tyre?

                        I should probably make it a clear question. If your front seat height is 490mm and your rear seat height is 420mm and you have a 26inch wheel and you were getting a new chair with 24inch wheels and wanted to keep the same pushing position, how much would you have to lower your front and rear seat height?

                        Thanks,
                        Rob
                        Last edited by rob1; 28 Jun 2019, 11:21 AM.

                        Comment


                          #13
                          Originally posted by rob1 View Post
                          hey, slow_runner yeah that would be useful if you could tell me the diameter of the 540 running Schwalbe Right Runs/Marathons?

                          Can anyone confirm the difference in diameter between a 26inch(25-590) wheel and a 24inch(25-540) wheel both running Schwalbe Marathons is 50mm?

                          I measured my 26inch(25-590) wheel running Schwalbe Marathons and from the floor to the top of the tyre it is 650mm. I would like to confirm what the measurement of a 24inch(25-540) wheel running Schwalbe Marathons is from the floor to the top of the tyre?

                          I should probably make it a clear question. If your front seat height is 490mm and your rear seat height is 420mm and you have a 26inch wheel and you were getting a new chair with 24inch wheels and wanted to keep the same pushing position, how much would you have to lower your front and rear seat height?

                          Thanks,
                          Rob
                          This I have done in the past.
                          If the rim width is 25mm and same for all rims. Unloaded. Not on chair. 130 psi or 9 bar. Not new tyre but not overly worn.
                          540 with marathon equals diameter 598mm or 23.54 inch
                          559 with marathon equals diameter 617mm or 24.30 inch
                          590 with marathon equals diameter 648mm or 25.51 inch
                          The marathon tyre adds 29mm of sidewall height from the clincher bead. Rim size is measured to bead not edge.
                          3 ways to fix seat height. Seat height is set from floor.
                          Relative to the world such as tables and counters. Don't change measures from existing rig.
                          Relative to axle. Shoulder to axle. Used by most fitters. Lower seat height by 25mm or 0.98 inch. This is the difference in radii from 590 to 540.
                          Relative to push rim. Shoulder to push rim. Changing this measure will alter your stroke mechanics. Difference in elbow crock angle is noticeable. To maintain from 590 to 540 add 25mm or 0.98 inch to seat height.
                          Altering seat height relative to axle alters vertical center which can affect horizontal center of gravity for some depending on individual characteristics.
                          Did these measures with old-style marathons. Current marathon material is a bit more squishy.
                          Hope this helps. Went through all this years back with help from schwalbe and tilite. Back when you could email them for tech stuff...

                          Comment


                            #14
                            I thought that I would check in before heading outside to prep and paint the Shadow foot plates/brackets and sorting out the dimensions for Rob.
                            You have saved me some time digging out the wheels from my shed; thanks Grunt .
                            I am sure that Rob will be appreciative too. The information is an excellent reference - Top marks.
                            Perhaps a sticky of such tech stuff is in order?

                            Comment


                              #15
                              I did a this wheel tire measuring a while back.. Running a 25" wheels with balloon tires that have the same diameter as 27" wheels with standard wheelchair tires etc.. so they swap out with no changes to brakes, CoG etc.

                              Using standard wheel chair wheels and tires so approximately 1" wide rims (23mm-28mm) seems to be the range.

                              Diameter of wheels plus tires, floor to max height of tires full inflated.

                              24" 540mm bead diameter - actual diameter with tire 23 7/8"
                              25" 559mm bead diameter - actual diameter with tire 24 7/8"
                              26" 590mm bead diameter - actual diameter with tire 25 7/8"
                              27" 622mm bead diameter - actual diameter with tire 26 7/8"

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