Let’s say you want to consider using a bicycle or alternate size tire on your wheelchair.
Based on the width of your rim, here are some recommended tire widths to consider.
Using the ISO Designation:
For example: the inner rim width of a wheelchair with ISO 25-540 (English 24″ x 1″) tires is typically 18mm. Looking down the column for a 18-20mm rim, we find that the tire widths should range from a minimum of 22mm (0.87″) to a maximum of 57mm (2.25″). Using the ISO designation, you could consider a tire measuring 22-540 up to 57-540 (width-rim diameter).
Using the English Designation:
There is no standard sidewall height for tires of a particular width, but a rule of thumb might be that tires have roughly a circular cross-section, so the sidewall height would be close to the width of the tire. Once again considering the 540mm wheel, a suitable tire would measure 540mm+(22mm x 2) = 584mm or 23″ up to 540mm + (57mm x 2) = 654mm or 25.75″ in overall diameter. Using the English designation the range would be 23 x 0.87 up to 26 x 2.25 (overall tire diameter x tire width).