Carry the main weight. The diameters of the wheels are 51, 56, 61, 66 cm. Except for a few use environment requirements and solid tires, pneumatic tires are mostly used.
There are several kinds of diameters of 12, 15, 18, and 20cm. Small wheels with large diameters are easy to overcome small obstacles and special carpets. However, the large diameter makes the space occupied by the entire wheelchair larger and inconvenient to move. The normal small wheel is before the big wheel, but in wheelchairs used by lower limb paraplegics, the small wheel is often placed behind the big wheel. It should be noted that the direction of the small wheel should be perpendicular to the big wheel, otherwise it is easy to tip over.